TH400 build-pictures

I was building a TH400 at 3 a.m. last night and had the same thought. :biggrin:

I haven't spent much time looking at them yet but I will check them out when I have a chance.

The Th400 will operate with only one checkball in place near the modulator valve.

One issue you'll find here,
shift calibration is somewhat subjective, mostly opinion.

I try not to make them shift killer hard, not reason to, and doing it from 1-2 will kill the sprag.

You could omit most of the checkballs on the TH400 and with a stock plate you'll still have pretty hard shifts becuase there is no restriction at many locations.

To do good testing you would need a solid unit (fresh), a stout car, and the time (spare is hard to come by), and play with it.
You would also want a combo with a tight near stock converter, so you get a better judgement of shift feel getting progressively harder with throttle.

I know the setup I use works, and works well, and doesn't break parts.

However it would be fun to spend a day and test about 6-7 different calibrations in the same combo.

I may try it sometime on my car. '69 Chevelle, 427 BBC, variable pitch converter (very tight in low stall).

Mine is setup to the above specs.

Pre- VP setup vids:

YouTube - Chevelle

YouTube - Chevelle Video
 
Also,
some of the factory 1-ton TH400's had the 3rd feed drilled to about 3/16". But they still had all the checkballs and accumulators.
 
jake most of the time you have a bathtub used for a splitter circuit.this is true at the low reverse passage.w/out this ball reverse oil will leak out the manual low circuit and cause no reverse.or intermittent loss of movement in reverse.like you said ,you are not breaking parts.that is where those balls and controlled orificing comes into play ,and without low throttle shift shock OF COURSE.
 
this thread is probably the most informative piece of trans tech ive read yet!!

thanks alot
 
All very good stuff! I wish someone would put together a new turbo 400 book, not saying Ron Sessions didn't do a great job. I would just like to see some good color pics and all of the latest and greatest tips and tricks in one source.
 
Some of you already know this, but my experiences:

Turbo Action's kit for the 400 just had a custom plate & the 2 gaskets. You still need the PR boost & the L-R check balls with it, but you leave the other balls out. We put it in 2 of our cars. It was OK, but not great.

I used the rebuilder type Transco SK400 Shift Kit on one of my cars, with all the springs, and drilled the 1-2, 2-3, and front band release feeds on the new plate to .140", and left out the Direct clutch exhaust check ball, GM started leaving that ball out in 1975 or so. It shifted pretty good, but not racing types of shifts. I liked the shifts in this car better than the Turbo Action kit ones, however. The Transco/TransGo kits increase line pressure as well.

I had a friend with the TransGo 400-2, HD sprague, and all flat steels in the clutches in his 402 Chevy II. Rear axle ratios also affect shift firmness; 4.11:1 gears would break the tires loose at even part throttle, but 2.78:1 would only do that at heavy throttle. We also noticed the TransGo 400-2's special plate had a .160" 2-3 feed hole in their plate.
 
TH 400 build

I would like to say thanks to everyone's input on my tranny build.The transmission shifts are crisp,better than my 2004-r.Car has alot of power so I'm taking it easy with low boost.All the modifications were done as described this thread including installing the check balls the way jake has them in his article and all I can say is that"I love my 400 Tranny"..The vacuum by-pass valve is a work of art.Next one will be the same to include extra clutches throughout..Thanks again guys,great stuff!!!
 
I would like to say thanks to everyone's input on my tranny build.The transmission shifts are crisp,better than my 2004-r.Car has alot of power so I'm taking it easy with low boost.All the modifications were done as described this thread including installing the check balls the way jake has them in his article and all I can say is that"I love my 400 Tranny"..The vacuum by-pass valve is a work of art.Next one will be the same to include extra clutches throughout..Thanks again guys,great stuff!!!

Thanks for the feedback. :biggrin:
Some here would claim they are the only ones who know how to calibrate a trans for proper shifts :rolleyes:

I like one to shift crisp at all throttle angles but not brutally hard, especially at light to part throttle. Most of us like a firm shift so we know it's there and we know the trans is functioning correctly. It's an "indicator" for us to use to let us know when something is going away. However there is no need for the parts breaking shifts.

My calibration has been installed in literally hundreds of TH400's over the last several years by myself and no telling how many others with my advice being posted on the internet.
I've had dozens and dozens of comments on how well it works.
I've used it in almost bone stock cruisers to 900+ HP turbo'd street/strip cars. One of those has been in service now for 3-4 yrs, no freshen up, nothing, just driven hard.

I've studied the checkball functions a bit more since this was posted and we are still installing 5 :cool:
 
I'd like to say thanks to all who donated to this thread with so much info. I now have one bad ass th400 with a CK rmvb w-brake and a Dusty PTC TC it's awesome solid firm quick shifts
 
I have read and re-read this post several times and have found it to be a wealth of information but not much has been said about the 1-2 shift other than to keep it firm, not harsh.
Question... If you are running the 34 element sprag drum and the 4 friction power pack what modifications should/can be done to the VB, spacer plate and/or accumulator, etc to firm up the 1-2 shift more than just drilling the spacer plate?
BTW I'm new to all this and TH400's so if I've asked a stupid question then please tell me. Rather than than not ask and forever not know!!! LOL
 
I have read and re-read this post several times and have found it to be a wealth of information but not much has been said about the 1-2 shift other than to keep it firm, not harsh.
Question... If you are running the 34 element sprag drum and the 4 friction power pack what modifications should/can be done to the VB, spacer plate and/or accumulator, etc to firm up the 1-2 shift more than just drilling the spacer plate?
BTW I'm new to all this and TH400's so if I've asked a stupid question then please tell me. Rather than than not ask and forever not know!!! LOL
on page 5 is a picture of accumulator modification(by-pass) and the other mod was installing the intermediate power pack(set up right)..and drilling plate..Basically everything in this thread is what I did to my tranny and 2nd is firm..Then more you step on the gas,the harder it shifts to 2nd..part throttle will kick the tires into second...also make sure your tranny has good pressure....I'm sure some one else will chime in some more info for you or you can send them a pm...hope I was able to help...
 
That has helped. It's made me look at the hydraulic circuit again and I now see that even tho the mod is done to stop direct oil flow going to the accumaltor it also looks like it makes the 1-2 shift firmer due to the spring being removed?? Correct me if I'm wrong!
 
Accumulator valve controls 1/2 shift feel.soft shift =a spring outboard of the valve,medum firm shift great for most applications=no spring on either side of the valve,super firm = a spring inboard of the valve(you can use a 400 int return spring in there if you like but usually toofirm for my liking).Keep feed hole down to 110 or the accumulator valve mods dont result in changes you can feel or shift shock.then there is the 1/2 accumulator spring in the servo.no need to play here it doesnt do much when you do what was previously mentioned.These mods are for auto shift obviously.
 
update

Tansmission is running perfect to date...getting ready to up-grade art carr 3200 converter to ptc 3800 stall....still smoking the tires on 2nd gear..:biggrin:

may have art carr converter for sale soon..
 
why such a high stall ?just wondering.

Sent from my SAMSUNG-SM-G920A using Tapatalk
Eight yr old thread. He probably has sold the car by now.

As far as the stall, It gets the boost room to spool and hopefully the converter tightens up at the top end.
 
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