01 grand prix gt, 3.8 engine, 4t65e trans.

**joeybrown** · 04-08-2011

Im not to sure where to start but here goes. When my problems first started with this transmission it would happen when the car was getting ready to shift into overdrive and it would chug. When I let off the gas for a split second and started going again it would go into OD just fine. It wouldnt do this all the time just once in a while. One day I was coming down the interstate doing about 75 and heard a weird whinning noise. When I looked down the tach was at about 4000 rpm's. When I got off the interstate and started going again after the stop light I noticed that it shifted fine from 1-2, 2-3 but wouldnt go into OD. The car still runs and drives but has no OD and with gas being 4.00 a gallon thats not a good thing. Once in a while now while driving the car, it will shift through the gears (no OD stll of course) but it feels like it has a shift kit in it. If I shut the car off and restart it, it will shift smooth in the first 3 gears. I was told by a guy thats a mechanic that does transmissions on the side that it sounded like the torque converter is bad. I also read some place that the PCS goes out on these transmissions. Im really hoping someone can help me out here with the problem because I sure cant afford to have it rebuilt right now. Also, if it is the torque converter or just the trans is bad, what years will fit my car? Thank you guys in advance for the help..

**FordMan77** · 04-08-2011

Any trans from 98 to 02 will work, but I believe the 98 has a different style of line on it but is swappable. Stick with a trans. from a GT and not a GTP as the gear ratio is different in them (3.29 in the GT vs. 2.93 in the GTP) and you would need a tune to correct for that.

As far as the no OD, it sounds like you have a stripped 4th clutch hub. the splines on the end of the shaft were not hardened at the factory and after years of hunting between OD and 3rd they wear thin and eventually round off, hence no OD. The RPM's you are seeing on the highway are normal for no OD. I drove my 00GT like that for almost a year before replacing the trans. I just kept it in "3" instead of "D" because I knew it would never hit OD anyway. Back the speed down a little and see if it helps your mileage.

Check the fluid and see if its full. If so, check the condition. Is it nice and red or brown/black? Use a WHITE paper towel to be sure on the color. If it's burnt, then try replacing the fluid/filter and see what you get. You probabaly won't get OD back, but the whinning may stop. It almost sounds like you have a clogged filter and the trans is starving for fluid.

**joeybrown** · 04-09-2011

If its starving for fluid, could it be the pressure control solenoid or something in the valve body? I was really hoping that it was just the torque converter..lol.

**BillBoost37** · 04-09-2011

I'm in agreement, likely it's the 4th splines and potentially a clogging filter. Likely it's not the tc or the valve body/pcs, but that doesn't make the overall repair of the 4th splines much easier.

**joeybrown** · 04-09-2011

is that something "easy" to replace?

**FordMan77** · 04-09-2011

If by "easy" you mean tearing the trans. down to get to it, then yes

**TheOtherNick** · 04-09-2011

Remove the trans, remvove side cover, remove 4th gear clutches, remove shaft. May have forgotten a step or two.

**joeybrown** · 04-09-2011

I know its going to be a big deal to take the trans out, just didnt know if it was something that could be done while it was in the car or not. Is it pretty basic once you get it out as far as taking it apart? I seen that a rebuild kit for this transmission is like 200 dollars. not to bad I guess..Can I also buy the 4th gear hub? If so are those expensive?

**FordMan77** · 04-10-2011

Yes, you can buy the new hardened 4th clutch hub. I know ZZP sells it, but you may be able to get it cheaper somewhere else.

As far as the rebuild kits go it can be done, but from what I've read there are some special tools needed to do it properly that add to the cost. If I have to do it again then I'm just going to pony up the $$ and get one from Dave at Triple Edge Performance so I won't have to replace it again in another 90K.

**2000gtpscreamer** · 04-10-2011

would the fluid from trans be nasty if the 4th clutch hub is bad? cus im having the same problem and the fluid is good and red with around 10k miles on it...

**FordMan77** · 04-11-2011

I wouldn't think the fluid would be affected to the point of burning it like you normally see when a trans. is slipping. Although running in 3rd at highway speeds will shorten the life of the fluid as there is excess heat being generated by the higher rpms.

**joeybrown** · 04-14-2011

Other then the gear ratio, would a gtp transmission go in my gt? Also what would the difference be between the gear ratios? Would it make the gas mileage worse? Please let me know how it would effect my car. Thanks again for all the help guys

**FordMan77** · 04-14-2011

Yes, technically the GTP trans will fit. The GT trans has a non-HD differential in it and has 3.29 gears.

The GTP trans has the HD diff. and 2.93 gears. So, you would actually get better mileage, but loose acceleration due to the lower gears. Cruising on the highway would net you the most increase in fuel mileage.

Downside- You will have to pay someone to tune your PCM to accept and properly operate the GTP trans. due to the difference in the gear ratios, otherwise you will have all kinds of strange issues (short shifting, etc...) because the stock PCM is programmed for the 3.29's. It will not "learn" the new ratio.

**joeybrown** · 04-19-2011

Thank you for all the information.. what other years transmissions will fit in my car? I found a 2002 that doesn't have many miles on it. Will it work? It has the same engine. Also can I just replace the 4th gear hub if id rebuild it or do I need to go in and replace everything else also? Thanks again

**FordMan77** · 04-19-2011

If it is an 02 GT then yes that will be a direct swap. Anything that is 99-02 will swap directly. The 98's and 03's are an odd duck. And don't bother with the 97's as they were vacuum operated.

You can replace/upgrade just the 4th clutch hub and leave everything else alone. Youl will still need a channel plate gasket and whatnot, but the rest is fine. May want to drop Dave a line and see what else he recommends be done at that time, or do a quick search in the trans. section and see what others have done. There may be a few other small things that you should replace while in there (solenoids, etc..). Not too sure on that one.