[90GMCVortec]

Hey everyone, I'm Kevin. i'm 15 and me and my dad have a 90' GMC 1500. we've just put a new summit cam and headers on it about a month ago. we were doing testing to find the best timing for it. we advanced the timing up pretty high and then took it for a test. we got on the gas hard and it started spinning in 1th 2nd and 3rd (But it was raining) but as soon it it kicked into 4th something happened and it dropped back into 3rd. it won't shift into 4th at all anymore. we stopped at a stop sign and when we went to take off again, we found that it wouldn't shift into 2nd too. from 1th the rpms would climb to about 3000 with light throttle and then kick into 3rd. with no 4th. we got home to see if the TV cable had slipped, but that wasn't the problem. we don't think it has anything to do with overheating, because we didn't run it hard for too long, and we have a trans cooler on it. could the 2-4 band slipped off its anchor pin? We don't think it had anything to do with the clutches, because we've replaced the clutch packs. What could the problem be?


edit: when we put it in 2nd manually, it feels like its in neutral

[Crosley]

Originally Posted by 90GMCVortec

Hey everyone, I'm Kevin. i'm 15 and me and my dad have a 90' GMC 1500. we've just put a new summit cam and headers on it about a month ago. we were doing testing to find the best timing for it. we advanced the timing up pretty high and then took it for a test. we got on the gas hard and it started spinning in 1th 2nd and 3rd (But it was raining) but as soon it it kicked into 4th something happened and it dropped back into 3rd. it won't shift into 4th at all anymore. we stopped at a stop sign and when we went to take off again, we found that it wouldn't shift into 2nd too. from 1th the rpms would climb to about 3000 with light throttle and then kick into 3rd. with no 4th. we got home to see if the TV cable had slipped, but that wasn't the problem. we don't think it has anything to do with overheating, because we didn't run it hard for too long, and we have a trans cooler on it. could the 2-4 band slipped off its anchor pin? We don't think it had anything to do with the clutches, because we've replaced the clutch packs. What could the problem be?


edit: when we put it in 2nd manually, it feels like its in neutral

Does reverse still function?

No 2nd or 4th gear indicates a problem with the band IF the trans still has reverse.

Band struts can break.

Double check the TV cable for proper adjustment and angles.

[90GMCVortec]

Originally Posted by Crosley

Does reverse still function?

No 2nd or 4th gear indicates a problem with the band IF the trans still has reverse.

Band struts can break.

Double check the TV cable for proper adjustment and angles.

Reverse does work not it acts like its in nu and the TV cable is in installed and set properly. it acts like its in neutral

[Crosley]

Originally Posted by 90GMCVortec

Reverse does work not it acts like its in nu and the TV cable is in installed and set properly. it acts like its in neutral

you will need to reword that, i do not understand the first half of the post.

Reverse works or does not?

[90GMCVortec]

Originally Posted by Crosley

you will need to reword that, i do not understand the first half of the post.

Reverse works or does not?

Reverse does not work

[90GMCVortec]

So reverse, 2nd and 4th no longer works. that could rule out the 2-4 band, but what could the problem me?

[Crosley]

Originally Posted by 90GMCVortec

So reverse, 2nd and 4th no longer works. that could rule out the 2-4 band, but what could the problem me?

that is a broken drive shell. That should have been caught during the rebuild as the wear on a drive shell usually is high and cracks are looked for too.

I would have a chat with the shop that rebuilt the trans.

trans will need to come out and apart for repair

a photo of the problem. broken splines or stripped out splines:

[90GMCVortec]

Originally Posted by Crosley

that is a broken drive shell. That should have been caught during the rebuild as the wear on a drive shell usually is high and cracks are looked for too.

I would have a chat with the shop that rebuilt the trans.

trans will need to come out and apart for repair

a photo of the problem. broken splines or stripped out splines:

Yep! that was the problem, it didn't stripe them, it sheared it off at the base. in other words it looks just like the shell on the right in that picture. Thanks for your help

[C-10]

An elaboration on the reaction shell thing.

They sell the 'beast' reaction shell as a fix for the above problem. Then I've seen the same shell machined some, then a torrington bearing put in place of the thrust washer normally found there... Does this defeat the purpose of the heavier reaction shell?

[Crosley]

Originally Posted by C-10

An elaboration on the reaction shell thing.

They sell the 'beast' reaction shell as a fix for the above problem. Then I've seen the same shell machined some, then a torrington bearing put in place of the thrust washer normally found there... Does this defeat the purpose of the heavier reaction shell?

Those fancy modified OEM drive shells can do this:



I'd buy the 'beast' drive shell. I have not seen one fail yet.

Those round holes in the OEM shell... are balance holes the OE punches out the material