1995 4t60e first gear issue

Hello everyone I am a first time poster in this forum and have a problem that is driving me batty at best. I will try to be brief and explain in detail, but I have a few questions about things that I found as I tried to diagnose the problem. could the fallowing problemo be a traction controle issue? I know what it is for but how does it work?


I yanked a known good tranny out of another 95 up donor car at a U pull it style junk yard about 2 years ago (78k miles). I installed it immediately and then did absolutely nothing with it until about a week ago. Oiled the engine and transmission, Fueled the engine, and snuck it out on a rural dirt road for a little test drive. The transmission works when in reverse, and Drive. But starting out, the darn thing will not go into first or any gear unless I manually shift into first. After moving, if you manual shift into second. The transmission will hold 1st gear and shift at the appropriate time. If the transmission automatically down shifts to first, it will engage first gear. It does WOT down shift into first appropriately timed and smartly.
I checked the resistance of the A&B shift solenoids, and they tested 19.4 ohms at 30F. I also monitored the solenoid states by jacking one front wheel and watching as the transmission selected appropriate gears. The states are changing just fine. When blocked with one wheel off the ground, the front wheel will turn enough to go into 2nd gear. But on the ground and blocked and braked in D, it feels similar to a smoked clutch or a low oil condition. Now hear is what is driving me nuts. When blocked, in D at idle, if I monkey around with the Neutral/gear select switch. It will engage 1st gear. This will happen by rotating the switch to the full adjustment clockwise rotation. BUT if you tighten the switch down and try to engage 1st gear by placing the car in drive…. No dice, it is the wet sponge again. ( not to mention trying to find a P/N spot to start the car)
Checking the neutral safety switch against a Function A B C P logic table is just fine and dandy when adjusted correctly. All functions such as P/N start work correctly, the backup light, power lock and unlock works just fine.

Now for the silly questions. Think that if I just drive the darn thing carefully starting out in with an extra-added heap of Magic Transmission goop in the mix, will loosen things up? Or do I need to replace a few seals in a servo, or accumulator? Hopefully… Can I get to the problem without yanking the darn thing out again? From what I can see the B and C logic at 1/1 is used to auto lock and unlock the doors. But the rest is stumping me what do they actually do? By looking at the table it looks as though it is dependent the entire host of sprags rollers bands and clutches. And what exactly does the traction controle do?
Thanks

This needs to be scanned with a trans function scanner to look at internal trans functions, especially solenoid operation, also look at the tps inputs and vacuum to the modulator.

OK I know that it has been a while since I posted the question, and I have not visited back because I just have not gotten around to fixing the problem. But I do need to fix the car because I need to drive the thing. I do know with the later obd I cars the engine can make some problems with the tyranny so I decided to get the engine running perfectly first. This is what I found wrong with the Engine that made it run funny after it was warmed up. Number three intake valve cracked, number 3 exhaust spring broken, and some where in there I must have popped the lower intake gasket because the darn thing started pulling only 11 inches of vacuum at idle. (By the way it did go into first better with only 11 inches, and how on earth it had 195lbs of compression cold and about 100 hot is beyond me) then I had to R&R the ignition coil drive board because it would cause a misfire on number 2 after running about 30 minuets. (now the engine runs perfect)

All that being said and corrected I have tried a new redline NAPA modulator valve. And a few used ones from the standard and HD tyrannies and I still have a no gears in first. Then I noticed that if I goosed the throttle and let go it would go into first. If I plug off the vacuum line to the modulator valve the darn thing shifts PERFECT!

Recording the engine/ tyranny states using a Acutron CP9185 scanner and laptop the engine group PIDs 1 and 2, the darn thing is doing what it should do when it should do it. SO again I will ask what on earth is causing this, and can I get to it with out pulling the tyranny and repair/replace what is wrong without doing a complete tear down. And, will it hurt the darn thing if I just drive it without the Modulator Valve hooked up? About the only other strange thing going on is: I have a secondary cooler installed in series with the factory radiator cooler that was pulled from a Ford Ranger because I plan on doing a little towing with it. I have done this before with a Buick and a 4t60 without any problems and have dumfounded the neighbors how I could pull a loaded car trailer all over creation. Not to mention pulling 1-2 ½ tons two to three times a week for several years without any problems.

Thank you

PS the darn thing just walked through an state saftey emittion test with flying colors with the Modulator Deceptively plugged

The modulator unplugged has no effect on an emissions test. Again the solenoid functions in the trans must be checked for proper operation using a high line bi- directional scanner that has trans function capabilty. I assume you mean it does start in 1 st gear, if so it may be in default.

I would like to take the time to apologize for asking silly questions in my typical long-winded anthems. After all I should know better to ask questions that I can typically answer myself because I know how to read and where to buy the appropriate books.



The 95 olds is OBD I compliant. That means that solenoid state is determined by engine RPM and VSS. This also means that beyond a good electronic knowledge and a good pressure gauge there is not much that a transmission tester can tell anyone that is semi competent. I agree that a Trany tester is a darn good replacement for an initial test drive but it will not give you any information that cant be had by jacking in a pressure gauge and monitoring all of your solenoid states with a good OBD I/II/CAN compliant scanner/reader. It is amazing what a little experience and the seat of your pants can tell you all by itself.
We also know that the modulator valve functions as the pressure regulator in the 4t60 transmission. Disconnecting it increases the fluid pressure providing enough pressure for proper transmission operation. This means that there is either an internal leak caused by hardened o-rings because of the rather long storage, or a contamination in the pump. (That is of course ruling out a plugged filter because it was new) and definitely not a bad solenoid. So after ordering the transmission book from Napa and using the best diagnostic tools on the planet, (my brain) I determined that the transmission would need to be pulled to find either crap in the pump, a blown pump seal, or a internal seal that is leaking like a colander. Because of the fact that even after several minuets of not moving from a dead stop in the OD position it sort of points to some thing other than a typically stuck accumulator.
So in a desperate attempt to avoid ruining two weekends turning wrenches. I decided to slop 3 quarts of transx into the mix and drive the wheels off the car with the modulator disconnected. After approximately 3 hundred miles the car notably began shifting harder. And after 4 hundred it was harsh. Reconnected the modulator valve to vacuum and it shifted fine. Drove another 200 miles and replaced the fluid and filter. Another 500 flawless miles even towing a 3500 lb boat, it is still working fine. Will it run another 130k miles? I don’t think so. Considering the fact that my original transmission was suffering from a granaded reverse reaction drum therefore would require a complete internal cleaning. This beats the complete rebuild hands down and the price was right. Less than 100 dollars invested. (two fluid fills, two filters, a book, and two cans of magic goop) hay at least I have the book for when I need it and I am sure that I will.
And by the way, with the modulator disconnected or stuck in the retracted position you will generate 1,2,3, and 4 gear selection codes, possibly a clutch slippage code, and aluminates the MIL. That means the car fails an emission test. In this state any car with more than two codes will fail. And car with more than 2 incomplete drivability tests fails. Even if one or more of the codes is silly such as, transmission temp to low, and “cannot set cruise above 85mph” and If the dash panel MIL does not light with the Key on and the engine off…… it fails.

Try disconnecting the modulator on an obd1 car it will not set a code, I am an inspector in NYS and have tried this, obd11 will eventually set a code. Also some trans codes will not set codes available with a normal scanner and require a scanner with a trans cartridge such as a Snap On mt2500. We both live in NYS, so I assume you seem to know the regs. any live emissions code will fail, or the cel naturally. People here try to beat the system by disconnecting the battery, of course without the drive cycle it will fail anyway. BTW engine load also figures in the shift solenoid commands. You are correct by getting the trans to shift with the mod disconnected points to an internal leak, good work on semi-solving the condition.