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tranny guru's: output shaft swap

muddybuddy

muddybuddy

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i finally got the right output shaft for my th400, so i just need to swap it in. how difficult is it to change the output shaft? can i do it by just pulling the pan, or does the tranny need to come completely apart? how hard is it? im trying to decide if i should attempt it or just take it to a shop and have them swap it in. thanks
 
you need to pull the frotn pump and the input drum, it is not to bad, if you have a clean space to do it and are careful it is pretty easy
 
The trans needs to come completely apart, the output shaft is the very first piece that goes into the case. IIRC there is one special tool needed.
 
TH400 can be done without any special tools IIRC...I don't recall needing any for just disassembly. The TH350 needs something to compress the rear piston assembly.

x2 that you need to take it completely apart though...valve body needs to come off, plus everything else internal needs to come out. But that's not THAT big of a deal. It will be interesting the first time you do it. :) (by completely apart I mean removal of major assemblies, not as in depth as breaking the clutch drums apart etc)
 
itll be the first time i tear into an auto tranny, so this should be interesting haha. im gona call a couple shops and see what they'd charge. im sure their quotes will scare me into doing it myself haha.
 
Since you can have a TH400 completely rebuilt for $500, why not do that and have the shaft installed at the same time? Since it will be torn down anyway, you should just spend the extra $100 and rebuild it.
 
kennyw said:
Since you can have a TH400 completely rebuilt for $500, why not do that and have the shaft installed at the same time? Since it will be torn down anyway, you should just spend the extra $100 and rebuild it.
Click to expand...

yea i know. i was originally getting a rebuilt 400 from a buddy so i was gona just swap the shaft in, but that fell through, so ill probably just get a core and get it rebuilt and swap shafts at the same time.
 
Unless your doing the labor yourself, replacing the output shaft will cost nearly the same as a full rebuild. The only difference is the cost of a rebuild kit, torque converter and maybe an hour of labor at most.
 
yea i guess so. my buddy whose got a built trans am got his tranny built by some guy who builds race tranny's, and said the guy charges $700-$800 for a solid race build for th400, so im going to look into that since i plan to eventually get a built motor. im sure a stock th400 can handle some big power, but i figure if im gona do it, im do it once and then never worry about it.
 
Watch out for a "FULL RACE BUILT" tranny... it will have options that are useless in a truck like a manual valve body. I have a stock TH400 in a 1990 K2500 Suburban that has lasted 275,000+ miles and is still going strong (with regular maintenence). I wouldn't worry too much about a stocker.
 
yea im gona give the guy a call and see what the deal is. i definitely dont want manual valve-body. apparently he builds them from mild to wild depending on what you want and what the application is.
 
IMO from doing a TH350, TH400, and TH200-4R, the TH400 is the best tranny to learn on, at least of those three.

The good thing is, if you tear down a running TH400 for just the output shaft, you can bolt it back together with all the same parts, and it should continue to run fine. Good way to get started IMO.

I think I was able to put my last TH400 (granted, it's been a few years) together, with a rebuilt converter, for about $200. I did nothing fancy to it, since the TH400 is pretty darn strong as is. I couldn't see trying to improve that unless I was pretty certain I'd kill it, and I knew I wasn't making that much power.
 
kennyw said:
Unless your doing the labor yourself, replacing the output shaft will cost nearly the same as a full rebuild. The only difference is the cost of a rebuild kit, torque converter and maybe an hour of labor at most.
Click to expand...

i just had a output shaft replaced on mine, cost $100 in labor, he had the output laying around. a full rebuild with good crap for a 400 ran me about $445
 
Grab a good rebuild kit from a online rebuilder and do it yourself...

most of the kits come with the instructions or there are cheap videos,,,
if you can read and follow instructions,, you'll be fine !!
 
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