Road Race Neon Transmission Woes

Hi guys,

I've been campaigning a 1st gen Neon ACR in SCCA ITA this season. During the first race of the season I lost fourth gear and everything went south quickly. I tore it down and needless to say there was a lot of debris. It's pretty hard to tell what failed first. Because of time constraints I decided to have a reputable shop rebuild a spare 3.94 T350 transmission. The gear sets were reused but a higher quality aftermarket (brass) synchros, bearings, and seals kit was used. I ran it this weekend but had problems again and am trying to decide on a course of action. 

Symptoms:

• Notchy/rough 2-3 upshift, 3-4 upshift, and 4-3 downshift in race conditions
• No issues when transmission is cold or during easy driving
• No problems noted with other gears. Clutch engagement/disengagement seems fine. Shift cables appear normal and fully to fully engage each gear. 

At this point I've tried changing the fluid to Amsoil Synchromesh, verified clutch cable adjustment is working, adjusted the shift cables, etc. Nothing I've found works beside driving around it but that costs a lot of time. My best guess is a faulty 3-4 synchro but it was brand new. What do you guys think?

I had similar issues with a t5 that I was road racing.

It ended up being clutch not fully releasing.

I was able to easily turn the driveshaft by hand with the clutch pedal pressed, so I thought it was fine.

I fought everybody who pointed to clutch disengagement....

I redid the system with another thin spacer and looked up the fsm for what the spec is.  

It turns out, it was like .040" of space was called for between the clutch disc and flywheel when fully released.  

After adjusting everything, the problem magically went away...

Verify you can stick something like a ziptie between clutch and flywheel when clutch pedal pushed.

I drilled a hole in the bell housing so I can see the interface and measure the gap.

When I start munching synchros, I know it is because my clutch fork is cracked again and preventing full disengagement.

(note: not a Neon)

In reply to wvumtnbkr :

This is what I initially thought but the problem doesn't seem to be in all gears. Looking in the inspection plate there is plenty of gap between the clutch disc and flywheel when disengaged. I tried shimming the clutch cable differently to no effect. I'll try to find a factory spec if there is one and measure it to confirm.

In reply to Knurled. :

I've seen that in other vehicles. The clutch fork in the car appears to be in good shape with minimal wear. 

What does Chrysler call for oil in those transmissions?  The older cars called for motor oil, but modern oils don't have the right additives in them to help with wear and it leads to real notchy hard engagement.  I started running 10-30 Mobil 1 extended life in mine and they shift great.

Id say your having oiling issues. I go between 10-30 Mobil one extended life (during the winter) and pennzoil synchromesh for summer and track duty. My DD has been on a ATF+4 diet for the last 180k. Its mostly a DD, been to the track twice, and 8 auto crosses. 

In reply to minivan_racer :

The FSM recommends a fluid that no longer is available. They switched to ATF+4 in later years but I think that was a cost save and isn't ideal. Supposedly those were used because of the material of the original synchros but they've been replaced with brass. I haven't tried Mobil1 yet but am running Amsoil 10W-30 Synchromesh.

In reply to Professor_Brap :

I think the next step is to try a different fluid for a test session. However, I can't imagine another synchromesh fluid will be much different from the Amsoil version that is in there now. 

You can shift quickly when it's cold but not when it warms up?  It might be worth trying a thicker gear oil.

In reply to APEowner :

I'm not 100% sure it's better when cold as I have never found an opportunity to try a fast downshift at high rpm when it's still cold. However, on the pace laps and first lap or so it seemed to shift fine. 

As I reread the original post I'm thinking the best thing would be to contact the transmission shop and see what they suggest.

enginenerd said:

In reply to APEowner :

I'm not 100% sure it's better when cold as I have never found an opportunity to try a fast downshift at high rpm when it's still cold. However, on the pace laps and first lap or so it seemed to shift fine. 

This is EXACTLY how my trans behaved also.  Once the system got a little heat in it, 5th gear was not available and the other gears were "notchy".

wvumtnbkr said:

enginenerd said:

In reply to APEowner :

I'm not 100% sure it's better when cold as I have never found an opportunity to try a fast downshift at high rpm when it's still cold. However, on the pace laps and first lap or so it seemed to shift fine. 

This is EXACTLY how my trans behaved also.  Once the system got a little heat in it, 5th gear was not available and the other gears were "notchy".

Interesting. I did verify clutch disengagement last night. At idle the clutch disc does stop spinning when the clutch pedal is pressed in. I can't imagine that clearance changes significantly with engine speed or heat.

As it has a new flywheel, clutch disc, and pressure plate and they are all a modular unit I think it's unlikely those are the problem. I've verified the clutch cable and adjuster work properly. The only thing that could be left if clutch disengagement was the problem is the clutch fork but it looked to be in good shape. 

I know my ACR did NOT like the amsoil. 

With a modular clutch it'd be basically impossible to check how loosely the clutch disc splines onto the input shaft. Even if you did have .04" clearance with clutch released, it would take very little looseness between the clutch hub and input shaft to get .04" runout at the edge of a 9" clutch disc and still be dragging against the flywheel/pp. Any lateral play in the input shaft would create the same effect. You might want to try checking for drag at 6-7k with the clutch in. 

A few more data points:

I checked for clutch drag with the car in the air. I put it in 3rd, pushed in the clutch, and went to about 6k rpm. Zero movement from the front wheels. I repeated the test with the car on the ground and obviously it didn't creep forward or anything.

I changed the Amsoil fluid to ATF+4 which some guys were running at the track. No change in symptoms. I think the only thing it can be at this point is the 3-4 synchro or 3rd gear itself...which is disappointing as it was just rebuilt. Will be pulling the transmission again next week.

Make sure and let us know what you find out. The more things it isn't the more i want to know what it is!

If your transmission specifies a type of ATF, then you should run Type F fluid.  ATF+4 or 7176 are super-slippery ATF.  Type F is the opposite, it is super-grippy.

I usually mix a quart of Type F to three quarts of 85W140 for my transmissions (80W90 is spec)  It's cheap, anyway.

In reply to Knurled. :

That was my thinking in trying ATF+4 but I noticed no change. That's been the recommended replacement since the factory fill became just about impossible to find. 

enginenerd said:

In reply to Knurled. :

That was my thinking in trying ATF+4 but I noticed no change. That's been the recommended replacement since the factory fill became just about impossible to find. 

One of the engineers who designed the transaxles does not recommend ATF+4:

In reply to red_stapler :

Yeah, I've seen/read all the Ed Peters stuff...lots of pushing Mobil1 High Mileage but there are also arguments that the blend has changed since then.  I do agree that ATF+4 isn't a great lubricant in this application and was likely used as a cost save that was safe for the OEM synchro material. As the synchros stop rings and such were replaced with brass components in the rebuild I decided to try other fluids. So far 3 fluids have resulted in the same problem so I don't think it is an oiling issue unfortunately.