Thread: Powerglide in Drag Racing

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I have a question for anyone who might know.
I have had my powerglide transmission rebuilt by my transmission guy, which is familiar with all the stuff.
The puzzling question is after installation you put it in gear and you give it some gas and it rolls forward just about a half an inch or so as you rev it then all the sudden it goes in in gear then you switch gears and it stays in the gear you were just in and then jumps into the gear you selected a few seconds later.
The Transmission was a Factory 1965 Chevelle 283 combo.
It has been rebuilt using all BTE parts including trans brake.
Any help on this I would greatly appreciate. Thanks!

Sorry, but that sounds like the behavior that I got out of my cast iron PG in the '57 Chev when I was younger. Girlfriends hated it, and it was due to some internal problem or other. Can't help more than that. Done right, the aluminum PG is a terrific trans for drag racing, but you need a wide power band and/or low gears. And lots of revs.

Valve body problems, maybe? That delayed reaction just doesn't sound right.

Sounds a lot like low line pressure. Excess end play, bad pump, etc. I'd ck. line and apply pressures and air ck. it first before yanking it back out. You'll zero in on it that way.

Didn't they have a combination, centrifical weight/vaccume governor on those???
That could be the problem.

I have presented the trouble you are having to my tranny guy to see if he can help. He is top notch when it comes to PG troubles, and uses BTE exclusively. I'll post his reply as soon as I get it.

Sorry to take so long. he he he Below is his reply.

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I would first check to make sure the shift link pin on the "rooster comb" inside the pan did not somehow come disengaged from the manual valve; the valve that slides in and out of the valve body to select gears. Also you could check line pressure at the servo cover test port on the right side of the trans. You should see at least 175 psi or so at an idle in low gear with your foot on the brake pedal. A shift to second with it sitting still and idling should not change things other than a quick spike down and right back up with line pressure. Then push the transbrake button with it idling in first gear; pressure should spike down and recover immediately. If anything is funny here with the tests....let me know! Hope this helps out!

Originally posted by SnakeHerder
Sorry, but that sounds like the behavior that I got out of my cast iron PG in the '57 Chev when I was younger. Girlfriends hated it, and it was due to some internal problem or other. Can't help more than that. Done right, the aluminum PG is a terrific trans for drag racing, but you need a wide power band and/or low gears. And lots of revs.

Valve body problems, maybe? That delayed reaction just doesn't sound right.

B
That's what I keep hearing but my transmission guy thinks it shouldn't be that because its a brand new valve body BTE brake
valve body, Another guy told me its the pressure relief spring in the valve body, so I am changing cases getting another pump shaft machined and going to reinstall, if the problem is still there I will put my friends already working BTE brake in it and see if it cures the problem. Hopefully the next time it works properly.
I do have the 1.82 gear set and a 4400 EDGE racing Custom built converter out of California, we will see how it launches then!
Thanks

Originally posted by pro60chevy
Sorry to take so long. he he he Below is his reply.

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I would first check to make sure the shift link pin on the "rooster comb" inside the pan did not somehow come disengaged from the manual valve; the valve that slides in and out of the valve body to select gears. Also you could check line pressure at the servo cover test port on the right side of the trans. You should see at least 175 psi or so at an idle in low gear with your foot on the brake pedal. A shift to second with it sitting still and idling should not change things other than a quick spike down and right back up with line pressure. Then push the transbrake button with it idling in first gear; pressure should spike down and recover immediately. If anything is funny here with the tests....let me know! Hope this helps out!

What kind of gauge do I need to check line pressure.?
The soleniod on the transbrake activates, but when I put it in low gear and apply it, it does not engage.
Does this sound like a pump problem?
or should I use A differant case?
Thanks for everyone's help!

Another reply.
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Q. What kind of gauge do I need to check line pressure.?

A. 0-300 psi with a decent line to ensure no leaks!



Q. The soleniod on the transbrake activates, but when I put it in low gear and apply it, it does not engage.
Does this sound like a pump problem?

A. not necesarily....if the solenoid does engage (and I am presuming the correct valve was installed into the valve body under the solenoid...yes, I have seen them left out..lol!!) then you have some sort of hydraulic issue. First confirm line pressure at the low servo port as first mentioned. Once I have some pressure readings to go on we can move along the diagnosis from there....also take a peek at my site Oldani Motorsports and click on the 'trans tips' page. Scroll down and look at the photo which shows the governor support and tin plate/gasket to use...this is for the 'pro' brake which is the one where you must push the button to back up. BUT, there are some mismatches that can occur with a non-pro brake that will leak reverse circuit pressure out the governor support. You need to pull the support and verify no leakage as some cases feed reverse down at the 7:00 position as viewed from the rear of the car and others feed through the support and into the case at the 11:00 position. If you have a mismatched support/gasket/etc. it can lose reverse pressure there, but that would have NOTHING to do with not having low or second gears. That is why you need to FIRST check line pressures!!! Hope this helps!!!

I got the powerglide working.
I changed the case to a newer case that did not have a rear pump and it works great! It picked my e.t. up from a couple weeks ago
About 3 weeks ago I put my TH350 in the truck with the same converter ran 7.38 at 91 or 92 mph with a 1.58 short time at best.
Now with the powerglide it ran 7.27 at 92 mph with a 1.52 short time spining about 3 revolutions out of the hole.
So its picked up nicely and shifts instantly. I shift the motor at 6,000 rpm and cross the traps at 6,000 so it worked out great!
Thanks for everyone's help and posts! Race on!

I sure am glad you got that thing fixed. Good work! Great times too. Drag racing is a blast!

Originally posted by us7
I got the powerglide working.
I changed the case to a newer case that did not have a rear pump and it works great! It picked my e.t. up from a couple weeks ago
About 3 weeks ago I put my TH350 in the truck with the same converter ran 7.38 at 91 or 92 mph with a 1.58 short time at best.
Now with the powerglide it ran 7.27 at 92 mph with a 1.52 short time spining about 3 revolutions out of the hole.
So its picked up nicely and shifts instantly. I shift the motor at 6,000 rpm and cross the traps at 6,000 so it worked out great!
Thanks for everyone's help and posts! Race on!

The truck has Surprised me again, tonight it ran it's best ever
it ran 7.09 at 93mph with a 1.494 Sixty Foot!
That was a big surprise I love that powerglide! Thanks