Conversion car, 88 TransAm with 98 LS1. Combo has been running for 2 or 3 weeks now and we've been working out a few bugs and trying to get a good tune on it. Basically stock except for CAI and exhaust.

Tonight we reset LTFT and started off to log some miles to get data to update the VE table. Everything was great for about 45 miles. Interstate driving trying to vary throttle position/speed to get all the cells covered. Running about 65 and gave it enough thottle that it should have downshifted, no downshift just a rise in RPM. Felt strange so we headed for home. Overdrive seemed to be working fine at this point. Exit interstate, pull away, good strong 1/2 shift but at 2/3 shift rpms just went up and no pull at all just like 3 wasn't there anymore.

Fluids and pressures look ok. Let it cool off and tried to drive again, same thing, no third gear.

Not much of a trasmission guy, I know the basics and may learn more here shortly.

Any suggestions on where to start trouble shooting, known problems to look at? My best guess is clutches are gone in 3/4 just hoping maybe there's some other known problem that's an easier fix. Got the tranny used off the board and seller said known good for what that's worth. Before it failed we had done several down shifts and they felt good and firm and hadn't noticed in slippage with normal driving.

Thanks for any suggestions!

 

Well, sounds like it was good when you started out driving it. Maybe you're low on fluid. Check that first, hot with engine running and on level ground. Did you hook up the brake pedal wire to release the torque convertor clutch when you step on the brake?

 

Checked fluid first thing when we got back into the driveway, it was right on the full mark. Yess the TCC stop switch wire is hooked up.

I've been wondering if this is just a 3rd gear only thing and not a 3/4 problem. Driving in 4, kicked down but 3rd wasn't there, let off 4th kicked back in ok and drove it for a few miles in 4 with no problem. Thought I might drive it this morning and command a 2/4 shift and see if 4 is working.

Trying to figure out where I can monitor transmission rpms in HP Tuners and also see if the TCC is locking/unlocking properly. Just got HPT last week so haven't got it down pat yet. Any suggestions on trouble shooting and where to look at things in HPT appreciated.

Tony

 

Im assuming you have the MAF unpluged right if your tuning the VE table? If so try plugging it back up & see how the trans reacts to that.

 

Not sure why this would affect it but I'll give it a shot, I'm open to all suggestions at this point. Want to make sure I've checked everything else prior to pulling this thing out.

By the way, when I checked the fluid it was appears to be clean with no off color and had no burnt smell at all.

 

The MAF plays a role in line pressure. When I first ported my MAF the trans wouldnt shift to 3rd without banging the rev limiter. Went back to the stock ends & have no problems.

 

Well I hooked it back up and no change but thanks for the tip I wouldn't have ever associated the MAF with the line pressures. MAF is descreened and I'm not sure if it's been ported or stock, came with the motor when purchased.

Trying to figure out where I can see pressures and such in HPT so we can try to monitor that, solenoids, etc.