1998 grand prix won't shift from 3rd to 4th

carlson74 · #1 03-12-2007, 04:21 PM

1998 grand prix won't shift from 3rd to 4th
Trans will shift correctly from 1-2-3 but won't even try to shift into 4th. no code, fluid is full, looks red in color and doesn't smell burnt. Other posts talk about the 4th gear shaft or a Solenoid issue. I can't fine any metal or debris in the oil.. I'm assuming it's electrical? Is there a way to test the solenoids?

BNaylor · #2 03-12-2007, 08:03 PM

Welcome to AF.

I would not assume anything until diagnostics is complete. A tranny shop can test solenoids with their high end scanner. The GM dealers use a Tech II scan tool. Or you can ohm out the shift solenoid coils. There are two. 1-2 and 2-3. Shifting determination is in the form of a matrix/gate through the PCM module and transmission range switch. For 4th gear (OD) the 1-2 shift solenoid is energized and the 2-3 is off, range switch 4th gear (OD).

Resistance can be checked at the 20 way connector tranny side.

1-2 shift - pins A-E 19-24 ohms
2-3 shift - pins B-E 19-24 ohms

Readings at 68 degrees F.

12 volts is always present on one side of each solenoid at ignition to on. The PCM module provides a ground/low.

BTW - It would help to post your model or engine size and which autotransaxle you have. '98 models could have either the 4T60E or 4T65E. RPO code M13 is 4T60E, M15 is 4T65E and MN7 is 4T65E-HD.

drjimmy · #3 03-13-2007, 12:38 PM

Mine was doing the same thing. Just had the tranny pulled today. Bad shaft.

The teeth are supposed to go all the way to the top.

The symptoms where not shifting into 4th. No codes. No engine braking in 4th. (take foot off gas pedal and rpm's drop to idle)

BNaylor · #4 03-14-2007, 05:06 PM

Thanks for the feedback drjimmy. Yours looks as bad as Troy1's. Off the top of my head that is at least 4 confirmed 4th clutch shaft/spline at Grand Prix alone over the last year.

troy1 · #5 03-15-2007, 09:18 PM

his is worse than mine

mine still had splines.

BNaylor · #6 03-15-2007, 09:31 PM

Quote:

Originally Posted by troy1

his is worse than mine

mine still had splines.

What I don't understand is why? Is it a manufacturing defect? It seems like you would have to be pulling a load/trailer way over the GVW in OD all the time. I'm surprised mine has held out all these years with all the strip time but then again I never make it to 4th gear crossing the finish line.

However, my overdrive works fine.

carlson74 · #7 03-15-2007, 10:18 PM

That exactly what mine does,,, when I let off the throttle the engine goes to idle.. Is this fixable? I'm a mechanic by trade but I've never done front wheel drive transmissions.. My car has a ton-o-miles but I would like to keep it as a spare with out putting too much money into it. swing it? or risk the repair.. I'm not afraid of attempting a repair,,, just wondering how hard it is..

drjimmy · #8 03-19-2007, 03:46 PM

Quote:

Originally Posted by bnaylor

What I don't understand is why? Is it a manufacturing defect? It seems like you would have to be pulling a load/trailer way over the GVW in OD all the time. I'm surprised mine has held out all these years with all the strip time but then again I never make it to 4th gear crossing the finish line.

However, my overdrive works fine.

Never pulled a trailer. I'm the only owner and I have never raced it. Does have over 120,000 miles on it.

maxwedge · #9 03-19-2007, 03:56 PM

The aftermarket and GM have revised the " stovepipe" with hardened shaft splines for this common condition.

guitarfish · #10 03-19-2007, 06:18 PM

I have a '98 GT with 220K and I'm holding my breath.

troy1 · #11 03-19-2007, 10:22 PM

Quote:

Originally Posted by bnaylor

What I don't understand is why? Is it a manufacturing defect? It seems like you would have to be pulling a load/trailer way over the GVW in OD all the time. I'm surprised mine has held out all these years with all the strip time but then again I never make it to 4th gear crossing the finish line.

However, my overdrive works fine.

Just cheap soft metal.

troy1 · #12 03-19-2007, 10:23 PM

Quote:

Originally Posted by maxwedge

The aftermarket and GM have revised the " stovepipe" with hardened shaft splines for this common condition.

That was on the 4T60E's Max 4T65E's don't have an issue with the "stovepipe"

maxwedge · #13 03-20-2007, 09:36 AM

Had to replace it my 98 LTZ with the 4t65e!!, and I know of others so it is both units.

BNaylor · #14 03-20-2007, 10:59 AM

This is just probably annecdotal information more than fact but I have never run across the 4T65E-HD versions having a 4th shaft/spline problem. Most of the failures I see where the 4th shaft is actually bad is on GT/SE model Grand Prixs. Also, the failures seem more predominant with the 4T65E autotransaxles that have GM RPO code M15 which is the one delivered with Grand Prixs and Chevys. The MN3 version of the 4T65E autotransaxles delivered with Buicks like the Regal, Park Avenue, LeSabre and Olds Intrigue don't seem to have as many 4th shaft failures.

Just to clarify the original poster should list whether he has a 4T60E or 4T65E autotransaxle and the model Grand Prix. The 98 models could have either. M13=4T60E and 4T65E=M15. Code is located on the SPID label on the back of the trunk lid.

'97 and up GTP/GTX have the 4T65E-HD GM RPO code MN7.

maxwedge · #15 03-20-2007, 01:06 PM

Bob, probably because "old farts" like me drive the Buicks less aggressively!

POST REPLY TO THIS THREAD