[Greg T]

Hi folks!! Newbie here to these forums and this place looks really good.

I have a question about my 1988 TH475 in my 95 S10. I am installing a B&M shift kit into it in a day or so, and while I was zipping thru the instructions I read about a checkball being in position #7 (factory) ONLY if the tranny was installed in a vehicle with less than 10,000 GVW. With vehicles of 10,000 GVW and more they remove the checkball at the factory. Does anyone know why this checkball is in there only UNDER 10,00 GVW and not in there over 10,000 GVW? Does anyone know for sure what this checkball is for? I could see removing it as per shift kit instructions or some other modification, but whay do they do it at the factory?
Thanx!!

[Greg T]

No TH400 gurus here?

[jakeshoe]

Factory calibrations differed.

I wouldn't use the B&M kit.

I usually suggest a TransGo especially in a TH400, it is the only kit that will dual feed the trans without internal mods. This helps the direct clutches live.

[briscoe]

I second that motion!!

[Greg T]

Originally Posted by jakeshoe

Factory calibrations differed.

I wouldn't use the B&M kit.

I usually suggest a TransGo especially in a TH400, it is the only kit that will dual feed the trans without internal mods. This helps the direct clutches live.

I understand it's a cailibration change. Do you know exactly what that one check ball does?

[briscoe]

Is the #7 checkball you have the option of leaving out beside the servo assembly hole in the case?

If so, this is the 2-3 circut. Many shift kits suggest you leave this ball out.

[Greg T]

Originally Posted by briscoe

Is the #7 checkball you have the option of leaving out beside the servo assembly hole in the case?

If so, this is the 2-3 circut. Many shift kits suggest you leave this ball out.

Nope, they wanna leave out #4 for street/strip calibration. The difference is the ball towads the center that only the 88 and up trannys have. 65-87 do not have this ball. Also, it says the factory leaves it out when the tranny is installed in a vehicle with 10,000+ GVW. In lighter vehicles the factory installs the ball.

[jakeshoe]

The checkball is not critical, otherwise GM would have always installed it. Checkballs usually force fluid to go through an orificed feed or exhaust hole instead of through a larger passage.

It is for reverse on an 88-up model IF it is the same as the #7 checkball in the ATSG manual.

We are somewhat working in the dark, as most transmission builders do not use B&M valve body kits. So when you are referring to their instructions we may or may not be able to decipher what exactly it is you are speaking of.

[Greg T]

Originally Posted by jakeshoe

The checkball is not critical, otherwise GM would have always installed it. Checkballs usually force fluid to go through an orificed feed or exhaust hole instead of through a larger passage.

It is for reverse on an 88-up model IF it is the same as the #7 checkball in the ATSG manual.

We are somewhat working in the dark, as most transmission builders do not use B&M valve body kits. So when you are referring to their instructions we may or may not be able to decipher what exactly it is you are speaking of.

Damn, I should have brought the manual home and scanned it. I've got the kit installed and the tranny buttoned back up already so it's kinda irrelevent now. But I was just wondering why they only used the ball below a certain weight. This would be the ball that is not included in the 65 thru 87 models.