GTP Consistent Weird Shift Into Overdrive (4th) Only When In "D"
- Thread starter iseektruth
- Start date
iseektruth
New member
That's what I thought at first, but wouldn't it do it when I waited til I got to 50 to put it in drive too then? It's very consistent at only happening when it is in "D" when it hits shifting speed. It doesn't do it at all if I start in 3rd and shift it myself when it gets to 50.
Scottydoggs
Killa Bee
i have to go park my car, so im going to take it out to see if it being in performance shift helps, haven't been really driving it in perf shift mode to much since i got the used trans put in, only 700 miles ago. this one has a shift kit too.
but what i described above my old trans also did. i to always thought it was odd how the rpm's would float for 200 rpm and then pull down the on the tach, yet you cant feel any of it, just see it. well at least when the cars quiet. :th_winking:
but what i described above my old trans also did. i to always thought it was odd how the rpm's would float for 200 rpm and then pull down the on the tach, yet you cant feel any of it, just see it. well at least when the cars quiet. :th_winking:
Scottydoggs
Killa Bee
the over drive wont lock up unless you let off the gas some, while in drive
when in 3 rd and shifting it manually to 4 th it should shift fast and solid, pulling the tach right to where it should be for that speed you are traveling at.
when in 3 rd and shifting it manually to 4 th it should shift fast and solid, pulling the tach right to where it should be for that speed you are traveling at.
Scottydoggs
Killa Bee
ok so with the perf shift off it floats a bit then sucks in (in drive) with perf shift on it i let off the gas some and it pulled into 4 th like a champ. and shifting from 3 rd to fourth while giving it gas in perf shift mode it shifted like it was a 2 nd gear shift lol, nice. i like my new used trans lol thanks again max!
iseektruth
New member
I usually let off the gas a little. I'll see what it does when I don't next time I'm going into overdrive.
iseektruth
New member
And for me, performance shift doesn't really make a difference if I remember correctly. It acts the same.
I should also note that it seems to lose power a little going up steep hills, but that might just be cuz I'm not pushing the gas hard enough to compensate for the incline.
I should also note that it seems to lose power a little going up steep hills, but that might just be cuz I'm not pushing the gas hard enough to compensate for the incline.
BillBoost37
New member
Ton's of good stuff in here already. Sooo I'll add to it.
Our transmissions are programmed to not lock the TCC until they are up to a certain temp. I forget what temp it is..I think it's something low like 100F.
When you are in third with the TCC locked up, it should release, shift to fourth and reapply the TCC. This is kind of what I hear you saying it's doing. Although since you are noticing it, maybe it's a little slower than it should be. On the HD trans (which you have) the factory programming on light throttle will shift into 4th right around 42mph. TCC can lock at that point, however it also might not. TCC lock/unlock is based on torque, load etc. Meaning if you are heading up a hill, your TCC can unlock to give allow the engine rpm to raise up and provide you with the power needed w/o downshifting.
A couple other things that factor into how your transmission shifts are the TPS, MAF and the ignition system. If you say had Platinum plugs in the engine, then they might cause you to have slight misfires or poor ignition and this could cause the pcm to be goofy with load calculations and shifting/tcc lockup.
Our transmissions are programmed to not lock the TCC until they are up to a certain temp. I forget what temp it is..I think it's something low like 100F.
When you are in third with the TCC locked up, it should release, shift to fourth and reapply the TCC. This is kind of what I hear you saying it's doing. Although since you are noticing it, maybe it's a little slower than it should be. On the HD trans (which you have) the factory programming on light throttle will shift into 4th right around 42mph. TCC can lock at that point, however it also might not. TCC lock/unlock is based on torque, load etc. Meaning if you are heading up a hill, your TCC can unlock to give allow the engine rpm to raise up and provide you with the power needed w/o downshifting.
A couple other things that factor into how your transmission shifts are the TPS, MAF and the ignition system. If you say had Platinum plugs in the engine, then they might cause you to have slight misfires or poor ignition and this could cause the pcm to be goofy with load calculations and shifting/tcc lockup.
iseektruth
New member
I'll ask my dad what kind of plugs he put in. They were replaced in August along with the MAF, the ignition wires, and the coil packs. Also, I noticed this before that. I'm not sure what kind if plugs were in before, but I guess they were fouled pretty bad. In fact, there was rust where the first wire plugs into the coil pack. What you're saying sounds like it might be what's happening.
And that makes sense about the temp and TCC, because it only delayed like that when it was below freezing. It would also explain why it doesn't make the sound when it's really cold because the TCC doesn't unlock and re-lock if it's not locked in the first place. It might be that it's doing it slower it I might just be overly observant because of the loud exhaust. If it is doing it slower, is it doing any damage, or should I not be concerned?
And that makes sense about the temp and TCC, because it only delayed like that when it was below freezing. It would also explain why it doesn't make the sound when it's really cold because the TCC doesn't unlock and re-lock if it's not locked in the first place. It might be that it's doing it slower it I might just be overly observant because of the loud exhaust. If it is doing it slower, is it doing any damage, or should I not be concerned?
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Brandonb0013
New member
I skimmed through all the comments and didn't see anybody say what I'm 99% sure the problem is. It happened to mine, sounds like exactly the same thing. It'll jump out of gear (4th/overdrive) on occasion. Gradually mine got worse and worse over a year or two's time. Turns out the 4th gear hub goes out on these cars quite often. Eventually if you're like me, you keep driving it and eventually you just lose overdrive because the gears get "stripped" so I was told. My advice, is if you plan on having the car for a few more years, get the trans rebuilt, and make sure they put the hardened 4th gear in. The shop I took mine to said they wouldn't put the oem one in anyway, but ask to be sure. That's my advice and my opinion on the problem. If you want more people's opinions, check out mnclubgp.com like someone said earlier. A lot of the people on there know a lot about these cars and modify them to 300+ wheel horse. In other words, they also know a lot and might be able to help diagnose the problem.
Chadgervais
Former GP Owner
That is really good advice. I often drive in a hilly area where the limit is between 35 and 55, i just leave it in 3. at 55 it registers 22-2400 RPM, i dont think thats a big deal.