I have a 1999 trans am, I recently rebuilt my trans mission about 3 months ago. Earlier today my trans mission started slipping between every gear while in overdrive. but if I manual shift or put the car into 3rd gearthe transmission never slips and I have no problem with it...any idea what the problem is?

 

The forward sprag is slipping.
The overrun clutch is (usually) engaged when not in [OD] which lets you drive the car that way. However go light on the throttle until this is fixed as the overrun clutch cannot handle much power (only two frictions).
Did you rebuild it yourself? If yes, then you should know where this is.
Heavier duty sprags are available for modest cost ($50).
Depending upon the damage to the current sprag, you may have to rebuild the entire trans to clean metal shavings out. Just need a gasket kit.

 

no I did not rebuild it myself but it is still under warranty from the person who rebuilt it, is this something they would've caused?

 

mrvedit is right on as usual. Replace the sprag with a heavy duty unit and you should be good to go.

 

And I assume I have to pull the transmission to fix this right?

 

Sorry, but yes the trans has to be pulled. Good that it is under warranty. Ask the builder to use a Borg Warner sprag and offer to pay the extra $20 over the price of a stock one.

Here is a similar recent thread that you might find informative:
https://ls1tech.com/forums/automatic...downshift.html

The symptoms were similar but not identical and it turned out to be a mis-assembled servo. It that thread it often wouldn't shift into 4th, but was not slipping in every gear. The slipping in every gear while in [OD] is a near-certain indicator of a slipping sprag.

Ted.

 

is it safe to drive it for a while by manually shifting the gears? and it doesn't seem to start slipping until it gets up into the 40 mph zone no matter what gear it is in

 

I would suggest that you drive it very easy until you can get this fixed as you risk burning up the overrun clutches and the sprag altogether sending this debris through the rest of the transmission and converter.

 

i don't plan on driving it very long just until the transmission shop can work me in or i can find another car, it's my daily driver lol

 

Well, I was going to take it to the transmission shop for him to drive it around today and see what he thought, but I got in the car this morning and drove around and it did not slip at all, since I think the previous suggestion is wrong what else could this possibly be? I didn't take it to the transmission shop as planned because I figured he'd just say there was nothing wrong with it at this point

 

http://www.facebook.com/photo.php?v=...54771879990168

I took it the the track last night and here's what happend over and over again my race starts at 1 min

Everytime it shifted from 1 - 2 in OD it hit the limiter and wouldn't shift and if i Had it in 3rd gear it would hit the limiter 2 - 3 but lose alll momentum from 1 - 2 I really need help, It's a full bolt on LS1 with a 216/224 cam with .550 lift running 9.21 and not even spinning the tires on street radials something major must be wrong

 

Mantrycarguy and I posted what we think is wrong. There is a possibility it is not the forward sprag, but it is almost certainly internal and it needs to be rebuilt.
You obviously did not take Mantycarguy's advice to drive easy, and part of your symptoms appear to be the overrun clutches now slipping. That is no big deal, but I fear you will soon be stranded on the side of the road.

 

mrvedit +1. If there were anything left on the overun clutchs before his trip to the track there is probably little material left now. Oh well, seems a complete rebuild is in order at which time he can replace the sprag and all of the friction material and steels etc.

 

just now dropped it off at the transmission shop, they said it was defiantly not the forward sprag clutch for what it's worth

 

Is there any chance my tune has something to do with this? I was rewatching the videos and I realized my car didn't even spin the tires and it's full bolts ons with 3.73 gears and a decent cam. The transmission shop told me when it was rebuilt a few months ago that it had a 3800 stall in it and the previous owner opted to put the stock stall in it, is there a chance it is still tuned for a stall? It also cuts off when you put it in gear when it is cold, I figured that was just a sign of the cam being a little big.

 

anyone?

 

When the PCM is tuned for a high-stall converter, the primary change is to reduce the WOT shift-MPH by about 5% to compensate for converter slippage. With WOT, both the shift-MPH -AND- the shift-RPM must be reached. Therefore a high-stall tune should have no effect when a stock converter is put in - it should still shift at exactly the same RPM. (A tune for a high stall converter might also eliminate misfire detection, converter slippage detection and a few other things - none of which affect driving.)

The tune also controls line pressure and shifting pressure in the trans. Nearly always the tune will have those set to max when the engine is at WOT. A really bad tuner could set those way too low, but I doubt that is your problem.

Have you scanned the PCM for both engine and trans codes?
If the TPS, MAP or MAF sensors are malfunctioning, the PCM might not know you are at WOT and could be setting the trans to minimal line pressure, causing slippage.

You took the car to a trans shop. Did they hook up a line pressure gauge and scanner to it? IMO a good shop will do that as the first step. You say they didn't think it was the forward sprag; did they base that on driving the car and experiencing the problems or just on your description? If your description to them was a bit different than what you posted here, that might account for the difference in diagnosis. Keep in mind that the forward sprag can partially fail where it will hold under light load, but slip under high load.

I recall a thread a few months ago where the OP reported similar slipping of a trans he had just rebuilt himself. I suggested that the forward sprag was defective or installed upside down. The OP opened up the trans and determined that the forward sprag was good and installed correctly. He then dug deeper and discovered that the Low/Reverse roller clutch (also a sprag) was defective. I don't know if he also replaced the forward sprag just to be sure, but I recall that the trans then worked correctly.

I suspect that having a trans shop connect a pressure gauge and scanner to your car and drive it to replicate the symptoms will let them diagnose it correctly.

 

yes they tested all the pressures and they drive it around, the only codes it are throwing is things that it should be throwing ie I don't have air conditioning so it's throwing a code saying it's disconnected, they said that all the line pressures were correct it's just not shifting like it should, it's been at the transmission shop now since Friday morning, they also said all the fluid levels were correct and it doesn't smell burnt so it's leading me to believe the problem is somewhere else and not in the transmission, hopefull they'll give me a call today and tell me what they found out from pulling the transmission if not I'm going to go up there tomorrow since they were supposed to have pulled it yesterday

 

and as far as I know hawks third gen did all the tuning