What transmission do i need?

what do i need to get for my transmission and how much will it cost. Well, i truly feel that everyone needs to have a transmission built for their particular needs and desire. this is why i truly believe no “off the shelf” transmission will make everyone happy. usually you end up paying a lot of money for something that gets the job done but really isn’t exactly what you want. i mean you have your engine built to your desire with a cam of your choice and compression/power/budget you want right…..well to me the same applies to your transmission AND rear axle. really they need to compliment what your trying to do otherwise you aren’t taking full advantage of your engine. you’re making due with a one size fits all tranmission. 

when it comes to the th400, it is a very sturdy platform to begin with so to beef it up to handle descent power is relatively affordable. although debatable, i feel in stock form it can handle up to around 400hp in stock form with good stock replacement clutches like a raybestos or borg warner. if you’re going to be using any kind of a shift kit, the next thing is to insure you have an aluminum direct drum piston as not all th400’s had aluminum pistons. when you push near the 500hp mark and are going to hammer on it at the drag strip or upgrade to a full manual valve body of some kind, the next thing is to upgrade to a 34 element performance direct drum sprag. this is the most common weak point of the 400 in 71-later transmissions…..and when it was retired and replaced with the 4L80, they went back to the older stronger sprag.

the next level is over 500hp+ and above 5000rpm, trans brakes, and nitrous oxide. this is a level that most derby engines never get to and if they do-they never apply the power fully. the first thing that needs to happen is to upgrade the input shaft and mainshaft must be upgraded to a hardened aftermarket shaft.  they loosen and snap. the direct drum and intermediate clutch should be upgraded to a 4 disc set up instead of the 3 disc stock….and you must modify or replace the direct drum and sprag to accomodate this. also thrust loading of the rear planetary can become an issue and planetary gears can snap when you get toward the 700hp mark and both straight cut and aftermarket 5 pinion carriers can be used as well. torrington bearings at the rear of the planetary and be machined and installed also.

now spinning a th400 over 6000rpm and up is somewhat of a rarety as a lot of bracket racers usually will opt of a lighter th350 or powerglide as they do not have to rotating mass and do not eat as much power as the 400 does. there are aluminum and lightened components out there to help the 400 in high rpm application hp, and you bend over and take it in the ass on price. so when you get to that point you should definitely consider all options on the table and look across the board at other transmission options for the price. you may want to go powerglide, th350, or even crower or a top loader manual at some point. i mean if the 400 was that great pro stock cars would use them….ya know what i mean? know when to say when.

the th350 pretty much was light duty from the get go and to put any real hp for anything over 250-300hp, you need to upgrade the center support to one out of a later model 4L60 or 700R4, and completely replace the direct drum and sprag assembly to an aftermarket sprag similar to the 34 element th400 sprag. also machining the aluminum piston down to accept 5 clutch discs on the direct is a good idea as well. there were numerous gearsets used on the th350 so you may or may not need to upgrade things like planetary’s and sun gear shell. BUT if you spend the money….the th350 WILL out perform the 400 as far as weight in the car and power put to the ground through the power range. here again- know when to say when.

the powerglide is the choice of transmission for bracket racing in my book. you pretty much have to gut it and use all aftermarket parts, but the consistancy is undeniable when you only have one shift point to worry about.

but as far as derby, the 400 can be built fairly affordable with stock parts and literally has the raw strength needed for the application over most other transmissions period. as i have stated in other parts of my blog, the th350 is not well suited for derby in my opinion, but some people have good luck with them. here again it doesn’t work for everyone.  a lot of guys like running a manual clutch, but for big shows most people go back the 400 and run their clutch set ups at the county fair to have fun. manual trannys for derby are inconsistant and to me it seems like it is a matter of when not if they will fail. the 727 chrysler is a descent tranny, and will work for derby. still not a th400.

1st/reverse only th400 works well for guys running less than a 4.56 gear in old iron and 4.10 in new iron. after that you wind the piss out of your engine. BUT i do know guys running 1st/reverse with 5.13 gears and scream across the track from one end to the other without a care. for the guys that like the 4.88 and up gears i suggest either a regular shift 400 that is modified for holding 1st gear(which is actually quite simple) OR a full manual valve body so you basically have a 3 speed manual transmission without a clutch. a lot of guys prefer the fulll manual over a regular shift as they can hammer 2nd gear to reverse and if they get to a point where they need to move a pile out of their way or their engine is overheating, they kick it down to 1st gear and bull doze around the track with the 5.13 gear. food for thought.

hope this helps guys.

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