Monthly Archives: November 2011

4L80E Transmission Teardown

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Well, although i have had this core for quite a while, i finally had the time to take the thing apart, document it, and most of all LEARN from it. this one in particular was a core out of a dumpster that i paid fair price for. it was missing the wiring harness and filter so basically what you see here is what i saw. basically the overall scheme of this tranny is a th400 with an overdrive unit glued infront of the front drum. the valve body is very similar to the same appearance and function of a 4L60 or even a 4R70W Ford. it is an aluminum valve body with a PWM, two shift solenoids, and a pressure switch manifold. what is absent though from the 4L80 that you find in the 700R4/4L60E is the TCC solenoid. the pressure regulator like the older th400’s is in the front pump. in addition there are also two TCC valves located in the front pump. i will get into detail on this a bit later, along with some model year stuff. unlike the 4L60’s and 4L60E’s, there isn’t as much info on these trannys easily found like there is on most others.

first thing to come off is the outer switches and cooler line fitting, specifically the rear cooler line fitting. there are two speed sensors to the left side of the case that you shoud remove to replace damage. also the shift position sensor. basically they moved it from the steering column to the side of the tranny and made the shift selector shaft longer. it has nothing to do with the internals of the tranny. you would also remove the rear cooler line fitting from the case. it protrudes into the center support and will make removing the rear planetary gearset damn near impossible. since the overdrive unit interrupts lubrication circuits that would have flowed similar to the th400, they re-routed the lube return fluid directly to the center support. anyways just don’t forget to remove the fitting.

After the pan and wiring harness removal,  the pressure switch manifold is next at this point. like the 4L60E, this is the signal manifold the connects to the ECM S3700022to let the on board computer know what the hell is happening in the tranny….and signal shift or set off idiot lights accordingly. it is help on by 6 bolts that go all the way through the valve body to the case and are an 8mm head. next is the clamp and steel lube line to the rear housing bushing and seal area. this is a 10mm bolt and clamp and is easily removed. anfter all that, you remove the rest of the valve body bolts and lift off the valve body assembly.

 

This leaves you with the valve body passage containing 8 check ballsS3700023, the low 2/front band servo, and you can also see the rear servo cover assembly like the th400 and center support bolt, but there is also a front support/fourth gear piston housing bolt as well. it is a torx head bolt.

 

 

 

 

 

hereS3700048 is a picture of the front bolt locationunder the valve body to be removed like the rear center support bolt on this tranny….and the TH400 trannys. at this time i would also go ahead and remove you rear servo assembly from the case so that there is no hardware left to interfere with the rest of tranny disassembly. the rear servo is VERY similar to the Th400 in that the rear band pin is an adjustment, but the piston, accumulator, spring, and cover are different. so don’t get the brilliant idea to interchange the parts.

 

Next, i pulled the tail housing. it is 6 bolts and although a similar pattern to a th400 tail, it is not the same. S3700028some of the 4L80’s used a tin oil shield like the older Th350 tranny’s did, some did not. they all had an internal oil seal thought. it may look like a roller bearing but it’s not. the rear bushing is actually smaller than a 400! if you have a tin shield it has to be removed, the seal does not. it can be removed and replaced later.

 

 

time for the front pump to come out.S3700026 first and foremost, remove the input shaft o-ring so you do not pull the guts out all over the shop floor. remove the pump bolts and like i do on the th400…..coax it out with a large screwdriver. pictured is what you should see. this is the front of the tubbine shaft/overrrun clutch assembly, and 4th clutch assembly to the outside of it. the center assembly pulls out like a forward drum assembly on a Th400. the 4th clutch assembly is held in by a snap ring and can be removed next.

 

the 4th gear clutch assembly housing/piston assembly can be removed and you are now down to the forward clutch. from here back it is damn near identical to the Th400 transmission. now although they may seem identical to the th400, not all the components of the aft assembly interchange. i will get into this in other articles. here you remove the forward drum, direct drum, low 2 bad, 4 disc intermediate clutch, and rear planetary/center support. the center support on these fits pretty damn tight to the case. they make a tool for removal, however i used a lead hammer and tapped it out of the case. i also used a big brass drift to coax it back home into the case during assembly. use good judgement when doing this if you are worried about it….don’t ram rod it!

700R4/4L60 Valve Body Overview

When is comes to this area of this line of transmissions, it is real difficult to nail it down. i have literally three different manuals open on my desk here and a catalog of footnotes i have gathered from builds i have done and advise i have gotten. so at best, this is an overview to give you an idea what to expect.

there are two major groups of valve bodies on this line of transmissions. what most people call a type 1:which is 1982-early 1987, and type 2: which is mid 87-92……often called an auxillary valve body tranny.  they are both a cast iron valve body similar to the older th350’s and 400’s.  there are 13 valve passages in the body. one being your manual valve, another being your TV, or throttle valve(which controls shift point like a vacuum modulator), and one passage believe it or not is is usually rendered useless on most transmissions for non-electric TCC engagement. there are then 3 primary shift valve passages for your main shift points. the 1-2,2-3, and 3-4 shift valves. these three valves receive oil signal from your governor and TV valve to trigger shift at the appropriate pressure signal. this leaves 7 more valve passages. these valves control downshift and accumulator characteristics and work in conjuction with the other 5 or 6 valves.

basically, during a standard rebuild, most people clean out the valve body with solvent then use a small screwdriver to make sure the springs on all the valves are not broken and the valves move freely. if there was a problem with the quality of shift at all with your transmission, you should buy the shift kit and follow the instructions. i have found that the primary source of wear in these things is the spacer plate/accumulator and not the valve body specifically. all of these trannys are prone for spacer plate wear to the point the check balls get stuck in the spacer plate. the accumulator also comes apart and beats the shit outta the plate as well.

Type 1 trannys use a fairly common midplate from what i can gather, differences being between diesel and gas models. most had 6 check balls in the case-one of em being larger than the other 5  for the TV exhaust port, and one for the accumulator housing.  there were also usually 3 check balls in the valve body on the opposite side of the spacer plate making a total of  8 check ball locations.

here you can see ach the type 1 installed on a unit. the upper left hand corner is you accumulator housing. this housing holds the 1-2 accumulator. below this accumulator under the mid plate is also your 3-4 accumulator piston. most early type set ups use a piston with a teflon seal. later type 2 set ups often used a different style piston with a rubber seal(which is considered more desirable and can be interchanged). the accumulator springs are also color coded for different tensions and shift characteristics. my transtar book list 7-9 different colors/springs here. from what i can gather black springs are thought to be the weakest and white the stiffest. the stiffer the spring the more aggressive the shift. red color being above average and blue color being just under that.  often these springs will have damage or be busted. also note that next to the accumulator is a flat plate…..similar to what a non-lockup th350 has to the front of the valve body. this is the location of the auxillary valve body on type 2 valve bodies.

type 2 valve bodies, also called auxillary valve bodies, are slightly more complex than the older trannys. the valve body is similar to the type one but is different. interchanging early and late model valve bodies is NOT recommended. also between 87 and 92/early 93 there were literally dozens of different style mid plates. there is even an interchange chart in the later model ATSG manual that at a glance…….seems like about 50 different plates! also the check ball locations change. the one later model i did for myself omitted two check balls over the type 1 i did. valve body gaskets are also different between the two valve bodies. TAKE NOTE OF WHICH GASKETS YOU HAVE DURING DISASSEMBLY! most kits come with 4-6 different gaskets. make sure you get the right ones or you will be in deep shit. gaskets are usually marked “C” for the case side of the mid plate and “V” for the valve body side, or lower valve body gasket.  one set will have a hollow pie wedge out of a spot on the edge representing the “V”, whereas the other type gasket will have a more distict “V” shape. which one goes where? well, take note during disassembly.

the Type 2 auxillary valve bodyt is located here, and has a tube that runs to the top of it from the front of the transmission. it bolts on in place of the rear cover plate location. GM started having trouble with a harsh engagement when shifting into drive or overdrive on some 700R4 models, which over a period of time not only irritated the customer but tore up the forward clutch of the transmission. so, in mid to late 87 they added this in place of the plate you saw earlier. basically it’s only job is to cushion engagement from neutral or park, especially at high idle which most fuel injected cars seem to do for a short period of time after start up. these are prone to having the center pin of the accumulator. there is also a check ball location beneath it. do not put it in the wrong port as there is an orificed plug next to the check ball location.

now i said earlier that there was a valve that is pretty much a dead slug in there. GM actually has a valve set up for hydraulic engagement of the TCC in place of the TCC solenoid and computer controlled engagement. most transmissions never got it and the factory installed two aluminum plugs in the passage to render them useless. sometime in 1989 they quit casting the bore in the valve body, but up until then you could remove the two aluminum slugs and put in the hydraulic valve set up for hydraulic TCC engagement. Companies like Superior make a kit to retrofit this valve into your transmissions so you can do away with the electrical lock-up all together. i have never done one of these, so please don’t ask me what is involved. i do believe the part number though is a K017, and is currently around 100 bucks if you shop around.

For performance, it seems GM had many parts that were corvette specific. so upgrading several parts in your 700R4 with corvette calibrated components seems to be a going theme. the TV valve in this case may not allow an upshift to 4th gear past 3/4 to full throttle. here you can get a different “corvette” sleeve for the TV valve in the valve body to correct this.

well, this is the last i am writing on these trannys for a while- my brain is fried now i need a cup of coffee!

Parasitic Drag/Oil Shear Effect on Clutch Packs

so something i have been trying to find a happy medium on transmission builds is what is largely known as parasitic drag. this is the amount of power it takes to make the transmission function. on a stock th400 it is around 30-35hp it taxes off the engine, whereas a th350 is about 10hp less than a th400 on the average.

parasitic drag i always thought was due to rotating mass and power requirement of the hydraulic pump. simply put, a hydraulic pump needs power, and the resistance to flow creates a power loss as well. you also have slippage in the torque converter as it is a fluid coupling(essentially a pump). internal components also have some weight to it. basically the more it weigh’s- the more it takes to get it moving. i’ll spare you the law’s of physics.

there is also something i have been trying to deal with lately called oil shear. on your clutch packs, oil circulates from the center out for lubrication and cooling. when the clutch is not applied, the surface area of both the clutches and steels are still covered in circulating lubricant oil. now, if we are spinning a dissengaged clutch pack at any kind of an rpm, the oil will sling to the outside…..literally sucking the flat clutches and flat steels together and causing them to drag. i want to say it is fairly similar to a kind of capillary action caused by centrifugal force. obviously a dragging clutch pack will increase tranny temperatures, and if severe enough, clutch failure.

the solution is basically put a relief area in the clutch pack for the fluid to escape. the easiest way to battle this is to loosen up your clutch pack clearances. this though is a catch 22 as if your clearances are too loose you will have other consequences.

the use of radial grooved clutch discs and waffle clutch discs are the best solution to resolve the problems caused by oil shear on most of your older trannys. gm did it on different clutch packs in both the th400 and the th350.

later model 4L80E’s and 4L60E transmissions used what is termed as turbulator steels. basically they are steels that have an oblong hole in the middle to relieve the oil shear caused by centrifugal force. they are found in the 97 and newer 4L80E’s in the overdrive clutch packs.

on the 96 and newer 4L60E’s , they used turbulator steels in both the reverse input drum and the low 1/reverse drum. ironically it is erie similar to the same areas that fail on a th350 in a demolition derby….anyways the late model turbulator steels can be swapped into earlier 700R4’s as an upgrade.

now as an example of oil shear. on my 1st/reverse th400, i got a guy that gives it time to shift, but floors it from one side of the track to the other all night in forward. after 40 minutes of running the piss out of his suicide lincoln……he loses reverse or it starts to slip. upon teardown there is nothing wrong with the seals- the seal rings-the pistons- the forward clutch is fantastic- gearset is fine. the direct/forward clutch is burnt to a crisp- i mean no linings. on a 1st/rev the direct drum spins just as fast in the opposite direction but dissengaged. even when using stiffer trans brake springs to keep the clutches dissengaged- the discs still suck together!

this is chronic oil shear….and can happen on ANY transmission used for demo derby. even with the use of waffle clutches, chronic oil shear still can happen. we are experimenting even to this day with combinations of different linings-number of discs vs number of steels, different fluids/additives, and clutch pack clearances to prevent this. there is no answer at this time for derby transmissions.