Monthly Archives: April 2011


316600931one issue that must be addressed on ANY build with one of these piece a shit plastic accumulators is that it MUST be replaced. the picture here to the left is a typical cracked piston from a mid 70’s bop tranny. starting in the mid 70’s most of the gm trannys had these in the valve body. the older ones had an aluminum pistons which are the replacement of these. over the years as trannys are rebuilt in the name of normal service, good builders replaced these with aluminum. so it is hit or miss as to whether or not you will have a plastic or an aluminum piston in your valve body. one thing is for certain, if you rebuild a tranny and don’t swap this out knowing full well it can crack, melt, and fall apart….you’re an idiot. so, this is first and foremost an obvious performance upgrade for any th400.  when this cracks it makes 3rd gear sluggish and you usually have to gun the throttle to get it to move in reverse.

3 setNow, the spring below the piston was different from one th400 to another….BOP’s may have had a softer spring vs a chevy truck would have had a stiffer one. quite often once there is severe abuse, these springs will break. so for heavy duty/race applications i chose to remove the spring render the accumulator useless. this omit’s a fluid cushion and make for a more crisp shift for the 2-3… well as reverse depending on your build.  you can accomplish this in a couple of way. if you have an older piston you can simply take the spring out and install it upside down. newer aluminum pistons have 3 tabs toward the top so you will have to grind those off to fit the valve body bore. the way i chose to do it is to install the piston in the bore completely, then install a 5/16″ set screw in the oil port next to it to block oil flow. the picture above is pointing to the port you tap and plug. i like doing it this way simply because your piston is installed correctly in the bore and the servo piston to the low 2 band will seat against the top of it correctly. now, if you have been paying attention……yeah the set screw might leak a bit, but the rest of the plumbing of the tranny via the servo will equal that of the 3rd gear circuit and the servo spring holds the whole works down .

the 1-2 shift accumulator sits inside of the rear servo. this is one of the places where bypassing an accumulator can effect numerous things. i have tried sealing off screws in the case-omitting accumulator piston seals, and all sorts of chicken shit. i wouldn’t suggest doin anything like that unless otherwise specified in an aftermarket shift kit or valve body per manufacturer. Gm had 2 or 3 different large servo springs over the years…not the small inner spring on the servo shaft itself the larger outer one….the most common are a blue spring and a yellow spring. i have found that the yellow springs were most common in heavy duty chevy truck applications and seem to be stiffer, so i prefer using that one and saying piss on it. the softer the spring-the softer the shift…and vice versa. it is not uncommon to find these springs busted upon disassembly. there usually isn’t much point in doing much with the 1-2 accumulator other than a large servo spring change in my book.

TH400 Direct Drum

351788749Now, one of the achilles heals of the th400 is the direct drum, which houses the 3rd gear/reverse drive clutch. the drum itself is a very strong piece. however, the intermediate sprag set up located to the rear of the drum is a weak link. some of my earlier blog post’s from way back address the different drums over the years so i am not going to rehash all of it. from the factory there were two styles- shown here is a pre 1971 drum with 16 element lug type sprag. 71 and later had 8 rollers…and they let loose and explode in heavy duty or race application. so, you want to start off with an early model drum. you then can get an aftermarket 34 element borg warner sprag that fits the older drum. the more lugs there are- the more it evenly spreads the load. when in 1st gear, the direct drum spins the opposite direction as engine rotation. to hit second gear, this drum comes to a dead stop to give you planetary action to create second gear. that shock load is immense in a racing application….and it’s not a matter if rather than a matter of when it will explode the roller clutch. in normal driving conditions….and to be honest anything up to 400 hp nbot using a trans brake or manually shifting….will usually handle a stock roller clutch. for full manual, trans brake, or heavy hauling, the 34 element sprag upgrade is a must. as a matter a fact on the 4L80 transmissions they went back to the 34 element lug sprag. i have been told the 4L80 drum and sprag assembly will interchange with an older 400 but never tried it as a total assy.

another weak link is the direct drum backing plate358343488. these things are prone to breakage primarily where system pressure has spiked or there was a clutch failure-it burned the clutch and overheated the backing plate causing it to crack. to keep this from happening, i ALWAYS make sure i use a rigid aluminum piston for the direct clutch . it is not quite as critical on the forward drum as it is not considered a shifting clutch. the stamp steel pistons will have a tendency to belleville/crown when installed in the direct drum from slam shifting and high pressure. this creates a wedge and in effect breaks the backing plate from the inside out as you can see by the picture. notice this one has an aluminum piston- the piston was cracked at the center  from a pressure spike due to a hung psi regulator-doing the same thing. so using an aluminum is not fool proof, but it drastically reduces fail rate. you can also use the backing plate out of a 4L80 which is made of a stronger material than the replacement 400 backing plates.


Another upgrade for a th400 that is a standard feature on the 4L80 is the spiro wound clip that retains the intermediate sprag. at high rpm, the stock retainer clip(laying on top in the pic) will have a tendency to release  due to centrifugal force. i have even seen some performance trannys go as far as welding in the stock clips to prevent this. although it is a bit of a pain to get it in, i suggest using the 4L80 spiro clip on all  performance trannys using the 34 element sprag. cheap insurance.

now last, but not least, is to apply both sides of the direct piston in 3rd gear application. primarily this is done by omitting the center seal of the piston and blocking oil port to reverse either using a set screw installed in the center support OR using a small freeze plug in the oil port of the case. you can also wedge a check ball in the port and stake it in place lARS017either. any one will work. you can also remove the second sealing ring down on the center support as well. this will allow the oil to flow more evenly into both passages of the drum to the piston. shown here to the right is an aftermarket direct drum and notice there is no provision at all for the center seal or seal ring for this reason. lightened billet drum are the cat’s ass, but they are not cheap and usually only last about 5 seasons for someone running a trans brake and a large bracket racing schedule. your wear rate may vary depending on manufacturer. you can also omit the center seal on the forward drum to achieve a similar effect for derby application only.

if you forget to plug the reverse oil port, it will lock itself up so don’t forget. what this does is give you full surface area of the piston to give apply force to the entire surface of the clutch. you will still have reverse as it will backfeed through the 3rd gear circuit. however, this mod will delay the reverse apply and for this reason should never be done on a derby tranny. this is only for street and forward race applications where reverse is not critical.


now, i am going to divulge a bit of a trade secret. shown here in the pic to the left is a center support and i am pointing to the 3rd gear apply port. this IS NOT the ony you plug for racing. the one you want for the modification above is the one to the right. the port at the center is the hollow bolt going to the intermediate clutch. now, i mentioned before that omitting the center seal creates even strong apply for 3rd gear. by omitting the center seal in a 1st/rev tranny you do the same in reverse. so you basically do the same racing modification ass396007831 backwards. ya plug the 3rd gear port and meter all your reverse apply through the reverse port. you control your reverse apply using a drill bit similar to the 3rd gear port.

another thing that i also do on 1st/reverse is to omit the intermediate sprag all together. like the check balls, it is unnecessary. you can then spot weld the lubrication ports to force extra oil to the planetary gearset

TH400: Check ball locations,shift kits, and mid plates

this is one of the things that a lot of guys will struggle with on both a th350 and th400, especially with all the rumors of guys leaving this one out-leaving that one out-drilling plates. well first off, for anyone who does not do this every day, you should really get yourself an ATSG manual, which is an Automatic Transmission Service Guide. they are available for most transmissions across the board and have very helpful charts and specs including check ball locations. i must also stress that although you can leave out check balls and drill ports, a QUALITY shift kit like the ones from trans-go are the way to go as they have not only a custom mid plate, but new springs and check ball locations to get the job done right. some kits also include extra springs for the low 1 band piston to severely limit accumulator action and/or make apply more aggressive.

but, if you are a cheap bastard like me, you want to try doing it yourself. well, yes you can, but it may or may not bring good results depending on the wear of the valve body springs you are using.  this is where a good kit with the springs will make a difference. i have fairly good luck with the th400 fabbing up my own stuff  so that is what we will be doing here.  on the th350’s, usually just buy a shift kit for street/strip, but fabbing your own kit on a th350 can be done.  i have never really persued it much to be honest and don’t see the point. i’m rambling again…..anyways, figure out what you want to spend and what you want to accomplish, then make your decision there. if you’re going to buy a kit, don’t waste your money on a cheap one that simply omits a few check balls and gives you a tin plate for a mid plate….that’s what we are going to do here.

bomber check ball


these are the 6 check ball locations found in most th400. i did a rather shitty job with a paint program to number them, but you should be able to get the idea here. 1 is for the modulator, 2 is the check in the 2nd gear oil passage that leads to the low 2 band, 3 is the check for oil going to the intermediate clutch(which gives you 2nd gear, 4 is the check located above the accumulator port(which to be honest i forgot wtf it really does), 5 is the check that bobbles between the low 1 and reverse oil ports to keep the tranny from locking itself solid while in low 1, and 6 is the 3rd gear check ball.

the only real critical check balls you must have under any and all conditions is numbers 1 and 5, the rest are there to block the port during clutch application but unseat to releave pressure rapidly. so, obviously by omitting 4 of the 6 check balls, you application and shift will be dramatically quicker….sometimes too quick. when i build 1st/rev or full manual set ups i only use these two check balls since there is no real point in having the rest of em if you aren’t shifting is there? for an aggressive street/strip i also will only use these two check balls and drill the 3rd gear port  in the mid plate to a 3/16″ diameter. you then calibrate your shift by modify’n the governor and adjusting the modulator valve so you get a hard shift at the right time. what we are doing here is controling the atittude of the shift, not the timing of the shift point, that’s the job of the modulator valve and/or the governor.

check ball number 6 can be omitted during ALL rebuilds, and even suggests that in the ATSG manual for a th400. on some of the 77-80 bop short shaft transmissions, there was no check ball port in the mid plate(even thoug there was a check ball for some odd reason), so to increase flow of oil to the 3rd gear you must drill the mid plate at this location for aggressive street/strip rather than the port shown in the picture below.


i found this picture that illustrates  both the second and 3rd gear oil ports in the mid plate of a th400. you are looking at it here from the upper valve body- or rather the case side of the mid plate. you will notice that while the 2nd gear port has the larger check ball  port next to it, while the third gear oil port does not. that would be the number 6 check. all oil is metered through this 3rd gear port for 3rd gear both in apply and disengagement, therefore you really don’t need the check ball. for agressive street or full manual valve body, you would simply leave out the 2nd gear check ball and drill the 3rd gear port with a 3/16″ drill bit. if you wanted to step up you shift to “firm” it a bit, you could leave the 2nd gear check ball in and drill both 2nd and 3rd gear ports to something like a 1/8″ or less to meter the oil orifice that controls the rate of apply. obviously the larger the port- the quicker more harsh the shift becomes. some shift kits even suggest just leaving 5 of the 6 check balls than drilling ONLY the 3rd gear il port to a whopping 5/32″ to give added oil flow for heavy towing conditions. i can only assume this is to improve holding of the 3rd gear clutch that drives you down the road most of the time.

now, modify’n the mid plate and leaving out check balls will only do as much as the rest of the tranny is built for. by that i mean you still have fluid accumulators for both the 1-2 and the 2-3 shift. so if they are still functioning, the shift with a 3/16″ hole may be just what you want whereas if you disable the accumulators(which is another article), a 3/16″ drill size may seem VERY aggressive.  in several builds for heavy towing, i will disable the 3rd gear accumulator, use 5 check balls, and omit the center seal from the direct clutch(here again another future article). depending on the mid plate you may or may not need to drill the 3rd gear port as well. you must know what the other components in the system are going to do before you go apeshit drilling everything out than….ooops.

TH400 :Holding 1st gear from automatic upshift in low 1

Well, i get this question 3 or 4 times a year. “When i am hauling ass across the track in low 1 the damn thing upshift’s right at the last second to 2nd gear and i lose all power before the hit!”  the other complaint is those of you guys using th400’s still for heavy towing applications, but you don’t see that very often these days because of gas prices, so pretty much the th400 is more of a performance item these days. i digress…….GM designed the th400 to force upshift even in low 1 to prevent engine damage. you usually have to hit 3500-4500 (depending on wear)and be on the throttle to make it upshift, but it does happen.  well, here’s the simple mod’s to hold the low 1 gear at all speeds .


First off, you must drop the oil pan and remove the valve body. you then remove the 2nd gear shift valve exposing the spool and sleeve assembly. there are three valves on this end of the valve body, all of which the pins remove from the case side of the valve body, so therefore the valve body must be removed to do this. there are the 1-2 shift, the 2-3 shift which has a spring at the rear against the retaining pin, and the smaller 3-2 downshift valve to the opposite side. you want the large 1-2 valve assy as shown.

On the spool valve, you then grind 3 small lands in the large area to the rear of the spool, of which there is an arrow pointed to it in the pic. this is to allow oil flow to bypass this area of the valve. you then must plug the exhaust port in the valve body itself, which is the other arrow in the picture. to do this you can either wedge a check ball in place, or what i do is tap it for a 1/4″ set screw and plug it using loctite….being careful not to tap and install it too deep preventing the valve from moving at all. i suppose you could also spot weld it…..but never done it that way since this is an area you do not want to warp otherwise the valves for the shift will bind! remember you must plug the exhaust port AND grind the land for relief on the spool valve otherwise it won’t work.

once you are done with this, re-assemble it and beat on it. it is obvious that this kind of a mod is a pain in the ass for something installed in a car, but it is a piece of cake during a rebuild. i do this for most all serious street/strip builds and derby guys who insist on a normal shifting tranny for derby. this way they can still hold 1st gear without issue.

TH350/TH400:modulator block off plug mod’s

302049547Well, this is the first in a new series of posts in the name of performance upgrades you can do for your transmission. what you see in the picture here is an aftermarket aluminum block off plug you can get from most any performance autiomotive supply outlet for about 10 bucks. it not only makes for a much cleaner appearance on you tranny, but in demo derby application it keeps the modulator valve from ripping off on the floorpan and causing a major leak.  unfortunately as i have stated a few other times  throughout my blog, this creates a major pressure spike while in reverse causing severe internal damage to the tranny. usually the modulator valve will act as a blow off valve while in reverse, but with this rigid plug it doesn’t move and deadheads the psi. well, i am going to show you the simple mod’s to get around this.

396007828Basically, what we are going to do is render the boost valve of the pressure regulator useless.  on a th400 shown here, the pump is removed to expose all the oil passages. the pick is pointing to the oil supply port from the reverse circuit. this supplies oil to the boost valve of the psi regulator that is in the front pump of a th400. we need to block this oil. here i have tapped it and installed a 5/16″ set screw to block the oil. some builders simply jam a check ball in here with a punch. Aftermarket valve body kits will simply omit the supply hole in the valve body mid plate to accomplish the same thing.

400boost01Now, this is not a total seal to the boost valve when using a check ball or set screw. Even though it stops the signal pulse of the oil, some oil may seep through and slowly raise the boost valve off it’s seal and trap the oil in the circuit so even when it is suppose to dissengage the boost valve- you have a high psi situation causeing internal damage in all gears- not good.  To solve this issue we grind two small lands on the large face of the boost valve. this insures the boost will not come off it’s seat.

using this modification, your th400 system pressure will remain a constant 155psi or there abouts in all gears where a stock blue psi spring is used. your main regulator spring is the sole psi adjustment now and obviously can be inceased with a stiffer psi spring, which are available aftermarket. you can do these mod’s and not install a plug-leaving the modulator valve in place to go along for the ride- it will still maintain the constant 155psi. this is more than enough oil and psi to make a th400 do whatever you want it to in my opinion. if you have to run more psi to make it shift harder- you really ought to be looking at modify’n your valve body and/or mid plate rather than increasing system psi.

Now, these modulator plugs can be used on the th350 asth350 boost well, and yes they also need some internal mods as well, but ironically we are going a slightly different direction. pictured here is the psi regulator valve ocated in the valve body of a th350. Basically, the reverse/modulator boost valve needs to have a “slight” relief cut into it on the land the arrow is pointing to in the picture. what we are doing here is creating a small shallow groove on the large land of this valve to bleed some of the psi off the circuit while in reverse. now, this is somewhat of a trick as if the groove is too deep you will bleed way too much psi off in reverse and burn up the clutch packs: not enough and it won’t bleed enough and it will spike your psi and also cause damage. the goal is to create a slight bleed of psi in reverse to keep the psi realistic in reverse. don’t get the brilliant idea to just weld the valve in place through the sleeve cause then there is no movement and your pressures will do goofy shit in several different gear range.  i usually don’t mess with it on the th350’s as the short modulator valve sticks out the back of the tranny and really isn’t in the way anyways.

Ford 9″ Center with Pinion Brake

396111114well, i got the opprotunity to go through a ford 9″ center section and install a pinion brake set up this week. this one is from Winslow Custom Shop in Abilene, Kansas.  i will make some comments about the brake later in the article. this center in particular, i used a lightened spool of unknown origin, richmond gear, and a basic run of the mill center section with small bearing caps. 

Now, Ford had a few variations of the 9″ center section over the span of many year. you had what i would call a standard case, a WAR case, and the Nodular iron or”N” case. 396111102 Standard late model case is easily identified by the single front center rib to the case. i have my parts dry’n on my tailgate after cleaning here and you case it pretty clear to the left side of the picture. a Nodular iron case has two ribs on the front of the case and is marked with a big” N” in the casting above the pinion directly on the front. these are the strongest and most desired- and are available aftermarket these days. the WAR case is identical to a nodular “N” case but does not have the big “N” in the casting. these were produced in the 60’s and got the nickname WAR because of the big W-A-R cast into them on the back side of the housing next to the carrier cap. although they look stronger than a standard single rib carrier, they are actually slightly weaker, so basically they aren’t anything special. guys actually took WAR cases and welded an “N” on the front so they could sell them for more money before the aftermarket arrived with new production “N” housings. so  when someone has a factory “N” case, pay close attention to look for this scam.

Another weak point on the Ford 9″ is the pinion and pinion support. under high horsepower, or slam shifting, or both…..the pinion has a bad habit of taking a shit right out of the front of the case. also the pinion has a rather small spline count so it can snap off easier than a GM 8.5  or a beefy Dana gearset.  Here again, the aftermarket comes into play with both heavy duty input housings and larger diameter pinions . all in all, a Ford 9″ is a power eating weak assembly in stock form, but the interchange capability’s at the track AND sturdy housings and axles make it a must for a lot of guys. the aftermarket axles, center sections, custom housings, andstronger internal components make this style set up very durable for most any application. You can basically build an entire new ford style rear axle these days and omit all the factory weaknesses if you have enough money.  There are even custom center sections on the market to put a 12 bolt gm style center into a Ford housing so you get the best of Both worlds. Anyways i digress back to the project…..

In my experience, older housings had a larger LM603049 carrier bearing, later model cases like this one has smaller LM102949 bearings.  larger bearings are more sought after because they can handle more load, but unless you have a stronger case to hold the bearings in, it is a mute point  cause the case will take a shit. in this case ,i got a used spool with large bearings and had to R&R the bearings with smaller ones. most spools for the ford will take either the large or small bearing, but the case is either or you cannot put large bearings in a smaller case or vice-versa. 396111101396111105Another thing that you will run across is when you go to install your ring gear to the spool, the factory replacement bolts are WAY too long and bottom out. in the picture on the left o ran the factory bolts all the way in bottomed in the ring gear to show you how much it is. the picture on the left is the carrier installed using a 3/4″ grade 8 fine thread bolt and red loctite. you should always use new bolts anyways for ring gear installation. i also recommend using good quality bearings like Timken bearings. yeah, you can use cheaper stuff and get away with it usually….i believe the Advance has National as their premier line of bearing along with China made stuff. i have had new National bearings fall apart just trying to press the damn things on the pinion and spool. i have never had issue with Timken and i use them in my entire maintenance fleet here at work as well.

Another Tip for the ford center sections-mark your carrier caps AND adjustment nuts to the side of the carrier you remove them from. this will make aligning everything up a lot easier. very similar to how you would mark your connecting rod and main caps on an engine for rebuild. it is also imperative to clean this part of the housing well for re-assembly. basically you sit the cap down flush to the housing and get your adjustment nuts settled in the thread spinning freely BEFORE you torque you carrier cap bolts. once you fully torque your carrier caps and have your assembly installed, the adjustment nuts should spin without binding and the carrier should spin freely. if it does not, you will not be able to get your backlash and carrier preload right to save your ass.

once you assemble the pinion and have the carrier installed, it is pretty down hill. 396111109you adjust your pinion depth with selective shims beneath the pinion support, and use a spanner wrench to adjust your carrier nuts to achieve backlash, and go by tooth contact pattern. it makes it a lot easier if you omit the support o-ring until final assembly. i outline some of this in a prior blog on rear axle set up. it is fairly easy compared to a Dana or 8.5 GM axle by far. once you get you get it where you want it, you preload your carrier bearings and install the locks and you’re done.

Now with the pinion Brake Kit, basically i got a brake rotor for a 95 escort that was drilled for a yoke, a custom CV style yoke,  a custom bracket to fit the outside of the support housing at the front, and a list of parts i still have to go out and buy. after i got my gearset dialled in, i had to go back and remove the CV yoke to install the bracket, then bobble the pinion, bracket , and 5 bolts into place. it helped to loosen the adjustment nuts on the carrier so i didn’t have to fight the mesh of the gears trying to line up all this bullshit. Then, i discovered the stock bolts were too short and of shitty grade. so i ran out to the hardware store and got some grade 8 bolts about 1 1/4″ long to compensate for the width of the bracket. i had enough room to get the torque wrench in and around to achieve proper torque. i went with a standard torque of 45 ft/lbs. other than not having support bolts provided(which i think should have), everything lined up without issue and looks to be a descent set up. with any aftermarket item for derby use, you have to expect a bit of fabricating. this wasn’t that bad. have fun!

The Original Warlord: Pt.4

190548_1900068617911_1127542558_32235499_7251568_n188573_1900069577935_1127542558_32235504_3141742_n195943_1900068817916_1127542558_32235500_7020513_n199279_1900068257902_1127542558_32235497_5370664_n196523_1900068417906_1127542558_32235498_858964_n205316_1900069137924_1127542558_32235501_7167623_n167790_1786825746910_1127542558_32075548_7478079_n168121_1786825466903_1127542558_32075546_6603062_nwell, this was the aftermath of two runs of the first two runs on the warlord. it was installed in a lincoln with rotted crush boxes. the real overall goal was to see if a tranny could be built to take all the strain and keep the nose of a car down by utilizing the floorpan. this was the raffle car at the blizzard bash in kansas dec of 2010, and another derby a month later. other than the bolt to the back of the housing rubbing through the floorpan, i would call it a success for the most part. it went on to compete in metal mayhem the next year, and two other derbies in the same mayhem car later that summer, both of which the car was victorious.