Dave Simkus

I need advice and help diagnosing the problem. I finally saved up enough money and got a very well built 4L60E.
I did keep my old torque converter, it was flushed and the shop told me it was fine to use. (yes I know it voids the warranty)

Anyway, I drove it very gently home from the shop. After about 5 miles as I was driving at about 40mph it downshifted to like 2nd gear and wouldn't shift back up. No weird sounds or anything just stayed in 2nd gear so I pulled over and turned the car off for a few minutes. Started it again and it drove perfectly fine again all the way home.

I've now put about 200 miles on this transmission and it still does the same thing. It drives really well for 5-10 miles and then 3rd gear disappears. Either while accelerating or cruising. I turn the car off for a minute and it drives great again.

Some Info:

Stock LS1 Trans Am

The converter I have is a cheap brand and I am going to replace it but could a converter cause this?

I haven't had the PCM tuned yet.

Could it be something caused by heat since it always happens after a certain time of driving? I didn't have a cooler installed.

Thank You for any help.

DietCoke

iTrader: (18)

This should get good...

Jake's Performance

iTrader: (2)

It sounds like a tuning issue. I would suggest getting it properly installed, tune included, before you ruin a good rebuild.

You are a transmission builders nightmare.... Used converter, improper installation, and the subject you post is who built it and it doesn't work...

Dave Simkus

You're right, I just changed the subject. They do amazing work, I didn't mean to imply it's their fault because it's not.

Thanks Jake. I did get it properly installed by a great shop that deals with their transmissions often and focus on muscle cars but I should of asked them to get it tuned too.

Problem is, I'm at my buddys house right now and I have to drive home 20 miles before I let it wait for a tune. Do you think It's alright to drive if I drive gingerly and slow as hell?

mrvedit

I would connect a scanner that can monitor what gear the PCM is commanding and the trans' temperature sensor. Perhaps you already know, but the trans makes no shift decisions by itself, it is all controlled by the PCM.
Since you have all gears when cold, I suspect the trans is OK and that for some strange reason the PCM is commanding 2nd gear when it gets hot.

Just a wild guess, but if the cooler line were clogged, the trans would get very hot, report the high temp to the PCM and it will switch to a safe mode. (There is a seperate HOT shift table.)

If you are sure it is not overheating, put the shifter in D2 and drive the 20 miles.
Sorry I don't know how to easily test for overheating; perhaps someone else does.

Dave Simkus

Thank You very much for that advice. Very helpful. I will try that. It does seem to happen after driving a certain distance, then when i restart the car perhaps something resets and allows all gears again. But I will allow the car to cool down just incase. I have to drive it home now, I'll leave it in the garage before I can afford to get a new converter and tune.

Thank You and everyone for the help.

mjs1012

iTrader: (36)

so youre running no tune no cooler and a used converter? asking for issues

mrvedit

So true.
Dave: When you said "No cooler" (which I missed in 1st reading), do you mean just the stock cooler, or no cooling lines hooked up at all.
(Can you even run the trans with no cooling lines at all???)

Bazman

I'm sorry you are having issues, that sucks. But seriously my tuner would not LET me drive away from his shop without a test and tune to make sure all was well.

I have a Level 6 4L60e RPM Trans under construction now, and I know my car will not turn a wheel until the tuner has checked the trans tune on the dyno. These are not 700's or Turbo 400's with an overdrive - the tune controls everything.

Dave Simkus

I'm using the stock cooler. I got the car scanned today and it said 'The ECM has detected a faulty combinations of range inputs from the transmission fluid pressure manual valve position switch'

Dave Simkus

Thanks, It's my first time having a new transmission so I didn't know it had to be re-tuned. I did get a check engine light when I left the shop and when I scanned it today it said 'Transmission pressure (TFP) switch manifold fault. The ECM has detected a faulty combinations of range inputs from the transmission fluid pressure manual valve position switch. Check for poor electrical connection, open or short circuit condition, failed transmission fluid pressure manual valve position switch.

mrvedit

That is not a tune issue. The pressure manifold switch in the trans is leaking/faulty or wasn't tightened down during the rebuild. That should be a trivial fix.

You didn't mention you had a Check-Engine light. First, you should have immediately returned to the shop to get that checked. Second you should have mentioned it in your first post.

Dave Simkus

Thanks for the explanation. I'm new to this so how far would the trans have to be disassembled to get to the switch?

mrvedit

Drop the pan (save the fluid), pull out the filter. Remove the electrical connector on the pressure switch. Remove the 5 bolts (3x 10mm, 2x 8mm) that hold it. Put in a new one ($25??) and reassemble, replace fluid.

BTW - The bolts are tightened to 95 in/lbs which is just 8 ft/lbs; i.e. just snug.

BTW2 - If you don't have a drain plug on your pan, you can pump the fluid out from the dipstick with a $8 fluid pump from Harbor Freight (or $12 at any auto store). Otherwise it can be quite messy.

The pressure switch is the rectangular plate in the upper right hand area with the 5 bolts:

Vince B

iTrader: (1)

How large of a stall speed are you running? Its been my experience that with over a 3000 rpm stall you will want to have two tests removed from your computer. These are P0751 and P0757. Both of which will trigger a limp mode condition. Your tuner should know how to remove these tests if you are getting a trouble code for either of these. HTH Vince

Dave Simkus

Thanks for the nice explanation. I would like to save labor costs and do this myself and it looks not too complicated. Honestly my only concern is putting the car on jack stands because I'm not sure exactly where to put them or where to jack from since there are so many contradicting answers on jacking in the forums. I need a clear picture of where to place jacks and where to jack up from. The first owner already bent the tabs where you're not supposed to jack > The rest seems simple even if I've never fixed anything before.

Dave Simkus

I don't know the stall speed, it came with the car when I bought it. I was told by the shop that installed my trans that the converter was some cheap brand (I think he said reman or something like that) After the install and all I have no money for a converter. I just want a stock stall or slightly higher.