Tourque Conv.? Throttle Body? Trans.?

nate2424 · #1 02-16-2007, 01:51 PM

Gentlemen,
I have a 98 Grand Prix GT. 191,000. No issues whatsoever till this point. for reference, Im in Detroit, (cold) and I have an Eibach pro kit on, plowing snow with my bumper.....
All of a sudden on the freeway, went to make a pass at aprox. 70 mph, car down shifted, and never shifted back. All other gears work fine, 1,2,3 but as I approach 60mph the RPM just keep on rising. Seems like it just won't shift into drive/OD. Has anyone ever experienced this? is there something I should look at? I took a look at the throttle body, but I am not sure what the proper operation is, so I am not sure how to diagnose if it is sticking....

Nate

BNaylor · #2 02-16-2007, 02:39 PM

That does not sound good. The shifting is controlled by the PCM module. But your problem could be a 3-4 shift solenoid/valve body problem in the transmission. Also, if OD - 4th is totally gone you may have a bad 4th spline so it could be a mechanical problem. When was the last tranny service....ATF & screen filter?

nate2424 · #3 02-16-2007, 02:45 PM

Thats the scary part, I bought the car @ 108,000 and never thought to dump the trans fluid. again, has always run smooth. Im afraid your right, I may have lost 4. How do I be sure? if I had it flushed, could it possibly rectify this? How is it that every thing else is working so smooth still and I have no 4? is this something that can be fixed, or is a new trans in order?

BNaylor · #4 02-16-2007, 02:56 PM

Either way unless it miraculously cures itself it is not a good situation to be in. A full flush used for when there are bonifide problems may resolve the issue or due to the mileage you have make it worse and you'll lose everything. Replacing the 4th spline is a major overhaul action and requires tranny removal/teardown. In the process other worn out parts should be replaced - rebuild.

You could drop the tranny pan and inspect for metal parts or excessive shavings/clutch material. The 4th spline literally strips and visible wear may be seen.

I don't think using your car as a snow plow helped but thats mother nature.

nate2424 · #5 02-16-2007, 03:11 PM

I will do that tomorrow and keep this thread updated. The next question is this, If I drop the pan, I am basically going to change the fluid anyway, what do you recommend? synthetic, standard?? Also, when I do this, say I don't see shavings, or un-normal wear, what would I look at doing next? or should we tackle that then?

BNaylor · #6 02-16-2007, 03:19 PM

Quote:

Originally Posted by nate2424

I will do that tomorrow and keep this thread updated. The next question is this, If I drop the pan, I am basically going to change the fluid anyway, what do you recommend? synthetic, standard?? Also, when I do this, say I don't see shavings, or un-normal wear, what would I look at doing next? or should we tackle that then?

You have nothing to lose by doing a pan drop. You will replace about 7.5 quarts of ATF in the process which is better than nothing considering your current mileage and unknown maintenance history. I would stick to dino regular ATF - Dextron-III like Castrol brand. If the pan drop service doesn't resolve the issue at least you gave it a try and then it would be time to make a major decision on getting the tranny either rebuilt or replaced.

Please keep us posted and good luck.

nate2424 · #7 02-16-2007, 03:25 PM

You dont think that it could possibly be the PCM, or something of that nature?

nate2424 · #8 02-16-2007, 03:28 PM

BTW, big Bobby Knight fan, Go Red Raiders. And thanks for the advice

troy1 · #9 02-16-2007, 10:27 PM

with that many miles and no check engine light I bet its the 4th shaft.

nate2424 · #10 02-17-2007, 05:24 PM

UPDATE:
Well, I pulled the Trans-pan, and the thing is as clean as a whistle, fluid is pink and clean, no metal shavings, I have a feeling from the condition of the rubber gasket that was in there that I wasn't a total idiot and I had changed it recently.
So now what I did was drive down the road at about 65mph, and I had my foot on the throttle to offer a little pull from the engine, and manually downshifted the trans to third, and nothing happened. This tells me I was already in third.
Then what I did was bring it up to about 70mph, and manually shifted into 3rd, not on the throttle, and then it definetly downshifted! When I manually shifted back, again, not on the throttle, it definetly changed the RPM. I dont know if it went into 4th or not, but it shfted to somewhere, Im pretty sure 4th gear is fine, not sure whats going on now. I am led to believe that it is definetly electrical...
anyone? beuler....beuler...??

troy1 · #11 02-17-2007, 10:47 PM

what happens when you give it a little gas drop back into 3rd? While coasting (foot not on gas) It should try 4th and because your coasting you really can't tell if 4th holds. I'll still put money on the 4th shaft. Do you know if you have a 4T60E or a 4T65E 98's can be kind of weird.

drjimmy · #12 02-19-2007, 02:48 PM

It must be a bad week for this because my 2000 just started doing the same thing on saturday. I was about to post a new one and saw yours. Called a tranny shop and he said bad shaft. $1600 cdn.

nate2424 · #13 02-20-2007, 10:46 AM

Bad shaft huh....Is this common? I can tell you right now a new Trans isn't that much, although it doesn't look like its going to be very fun to replace. damn.....did you have the solenoids, and the system checked for codes? It engages the drive gear up to about 2500 rpm, and then downshifts after that, at about 50 mph.....
Im wondering if it is the same, Im inclined to think my problem is electrical, Ive heard this weekend that there is a solenoid in the trans that goes bad as well. Im going to have to look into both.

BNaylor · #14 02-20-2007, 11:16 AM

A bad 4th shaft/spline is a common problem because the shaft was not hardened. Replacement shafts are. I don't recall the cutoff year. The hub/shaft is part of the 4th clutch. No clutch no shifting/gear.

Good idea to rule out other possible causes but I would take the advice of Troy1 since he is a tranny pro and works on these POS trannies for a living.

Even if it were a solenoid it is still a major repair job which could cost in a range of $500 and up. See thread below which is in our Tips and Maintenance section for solenoids.

Click here

nate2424 · #15 02-20-2007, 11:37 AM

alright, before taking it somewhere and having them put a tech II to this thing, (or would you not even recommend that?), lets say it is the 4th spline. what are my best options? is it like drjimmy said, Im out the $$ for a trans?

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