73aussie455

Hi all.
Well it looks like the motor will need to come out for the mods I want to do, and then I MAW detail the engine bay somewhat as I've been spurned on into action by some of the great threads I've been reading.

So I MAW also take out the TH400 and clean it up too after an inspection.

Question is, has anyone done the mods that firm up the 1-2 and 2-3 shifts I've been watching on youtube, ie drilling out the 2 & 3 feed holes, leaving the spring out of the 2-3 accumulator piston?

Has anyone had success with these seemingly basic free modifications?

brddg

MAW buy a shift kit.

Fun71

I agree, buy a quality shift kit like a Trans Go.

nsnarsk65cutlass

Modifying a used trans is not a good idea,now if it's being rebuilt that's ok.Nick

455man

I've done those mods on a tranny that was given to me about 15yrs ago. My TH350 went out so i took the pan off, drilled the holes a little bigger, pulled the spring, took out a few checkballs and put it in the car. It shifts good. Got about 10k miles on it after the mods. No idea how many miles are actually on the tranny but I dont think it's ever been rebuilt.

Octania

"took out a few checkballs"

Seriously?
8-0

Just removed a few parts at random, or was there a clever plan to this?

455man

Seriously. Some tranny's come with 6 checkballs and some are not needed.
http://www.jegs.com/InstallationInst.../130-20260.pdf
Step 9 and figure 11 explains which ones to keep. I figured the OP knew about the checkballs since he has researched it.

73aussie455

Thanks 455man. I have researched the mods extensively and am considering some of them for my TH400. I really wanted to hear from someone with REAL experience doing these mods, not just the virtual cyber ones so thanks for that.

Octania, these transmissions have been around for long enough now that some very clever trans mechanics have, through trial, error and time, worked out how to get the best from them and how to mod them without doing damage, to suit their particular applications.
There is a wealth of info out there on modding the TH400 and 350 transmissions to various levels of performance. There is a standard set of easy basic mods that have been tried and tested over time, so I would feel confident I'm not screwing up my trans. Yes, a shift kit does give the same mods but i'm a tinkerer kind of guy.

Changing shift points by changing the weights also doesn't seem so hard when you research the process, but just a little more complicated.

matt69olds

If your comfortable removing the pump and valve body this is basically what I do for my street performance transmihttp://jakesperformance.com/TH400_Rebuild_Tech.htmlssion builds

Get a service manual that covers TH400 overhaul procedures. Trans-Go is the only shift kit that can dual feed 3rd gear without transmission dissasembly. In my opinion, if the transmission is out of the car, following Jakes tips is a much better and cheaper way of doing it. The shift kit does the same basic thing by blocking the hole in the case where you would have to install the freeze plug, and blocking the hole in the valve body where you would install the set screw.

If your using a stock converter or slightly above stock follow trans-go or Jakes drill sizes. If the stall speed is in the 2800-3000 or higher range drill both holes to 3/16th. If you can locate an extra horseshoe shaped shim for the pressure regulator valve use 2 and the stock blue spring, this will provide about 180psi of line pressure.

If the transmission is in good shape installing a shift kit wont hurt anything. If the trans needs rebuilt or is nearing the end of its life following these instructions, with good performance friction clutch plates a TH400 will easily handle 600-700 hp.