Game ova

I've done some research on the subject of restricting the feed circuit on Th400s. It seems that some get away with not restricting, but then there are guys who have what's been called a "Killer 400". Is there any way identify one of these killer transmissions by year, or anything else? And are any of you turbo guys having success with simply running the transmission as it was designed? Not sure if it matters, but my transmission is an '88 th400 and I'm using a PTC 9.5 inch converter.

Game ova

Anyone??

Dimeomboost

Without sounding idiotic I don't exactly understand the question when u say run the transmission as it is are u asking about just running it as it came from the factory ??

Game ova

I may have worded it a little funny. What I'm looking for, are guys running the 400 without modifying/restricting the converter circuit....and not having thrust bearing issues. I've read about some guys having thrust issues, just not sure if it's always transmission related. I really don't want to be restricting flow to the converter if it's not really necessary.

PBA

To eliminate the thrust bearing issue, you need to remove 2 splines on the input shaft 180 degrees apart. This will solve the balance issue here. GM knew about this back in the late 1960's early 1970's. I have seen this happen to 454 BBC's taking out the thrust bearing. Once this modification was made, it never happened again. Talking to John Kilgore, he has been doing this for many years to prevent this. Some GM TH400's had these two splines removed from the factory on very few 1970 W30 Olds, Buick GS Stage One and Pontiac RA IV & V TH400 transmissions.

Dimeomboost

Well that's new to me my 5.3 block had no issues with the th400 not sure y and the 6.0 doesn't either seperate cars separate transmissions neither has had an issue but maybe I should be looking more often to make sure

Game ova

Did you get your transmissions from a race oriented performance shop?

Nathaninwa

Doesn't a lot of it come from a ballooning converter. When doing a turbo build you should have a custom one done anyways, usually with a billet front cover and antibalooning plate

forcd ind

iTrader: (7)

When I pulled my engine last winter for a rebuild, the thrust bearing was eaten up-I went thru the trans also, and decided to plug the hole in the pump and drill it out to a smaller size, but I never hooked up a gauge to ck the pressure-I don't plan on pulling the engine, but am changing the pan, so at that time I will ck the thrust bearing.
Was the converter ballooning, was it pressure that hurt it, I don't know-I also had a new converter built, and had a balloon plate installed.

Dimeomboost

no mine is a regular short tail th400 from a truck I think . It's just got a better pan on it and has been built to hold the power better but is not a fancy unit from any well known race trans builder or anything like that

Game ova

I'm using a PTC converter built for turbo app. Custom made for my lil setup.
See, this is EXACTLY what I'm afraid of. I'm leaning towards just going ahead and restricting it just to eliminate the possibility of this very issue. Are you running a FI setup?

forcd ind

iTrader: (7)

Yes, fuel inj/turbo
There is a guy that sells a kit that limits pressure, I think it goes in the cooler line-Hutch, he is the mod in the trans section on Yellow Bullet

Jays_SSZ28

iTrader: (2)

The converter ballooning is not the problem, thats just one other thing that can happen from excessive converter feed.

Excessive converter feed pressure pushes the converter out of the pump and into the crank pilot. And obviously pressurizes the converter.

FTICONVERTERS

iTrader: (3)

We fix this issue inside the pump of the Th400. We also have a Charge pressure blow-off valve kit that we use for turbo setups to allow for a more efficient converter that will still spool up. We open back up from our holiday vacation tomorrow if you would like to give us a call and speak with one of our transmission techs.

Game ova

Will check with you when I get back in town. Will be on vacation till mid month.