I have been having shifting problems with my '98 manual transmission for several years and hope that there may be an easy fix such as an additive or external adjustment. It has become increasingly more difficult to get a firm engagement in 1st and 2nd gear, especially when the car has been driven for a while. Although it may feel like it is first gear, sometimes it will pop out when the clutch is let out. Going into second gear will feel like it is fully engaged but may grind as the clutch is released requiring additional force to engage it. In recent months I have noticed that I may get a grinding when shifting from 5th to 6th if I'm not real careful. I never have problems with 3,4, or 5 gears.

I think that I am fully depressing the clutch everytime it happens but have never changed the hydraulic fluid since new (now with 56,000 miles). Discussions with other Corvette people have suggested an ATF fluid change which didn't improve the situation a couple of years ago. Speculation that my late '98 had some inferior parts before Borg Warner was replaced by Tremec can't be determined without a transmission inspection/rebuild. Worn synchros could also be a factor but was not confirmed by a test drive by a Corvette mechanic. My C-5 Forum research hasn't identified a similar problem so this may not be a common complaint. Therefore, I'm hoping that some one might recognize these symptons and be abe to give me some direction to follow. Would a specific synthetic ATF help this particular transmission model? Are there any "magic" additives available? Any suggestions would be greatly appreciated!

 

Change your hydraulic fluid by the dilution method and just change your tranny fluid. Check for metal shavings. If you aren't disengaging completely you will prematurely wear your synchros out.

 

Many thanks for your suggestions vettesrgt8. Sounds like you have seen this condition before. I'll change the clutch and tranny fluids. Will a particular tranny fluid make any difference?

 

You have paper blocker rings inside the tranny and the only fluid other than stock ATF that I would run would be AMSOIL. Contact Subdriver and get the skinney on correct ASMOIL that you need. I put MOBILE 1 Synthetic in my 98 without any issues but, now I know better.

Yes, changing from dino ATF to synthetic ATF made a significant difference for my 98 and 02 ZO6. You have to make sure that the CLUTCH is fully disengaging when you have the clutch fully depressed.

Jack up the back of the car. Put the trans in first gear with the clutch depressed. See if the rear tires spin and if they do how much force are they spinning with?

With the clutch depressed, they should not spin. NOTE!!! They might move a little if the trans is very cold but,,,,if the tranny oil is warm,,,when the clutch is depressed, it should not transmit any rotation to the wheels.

If you have a lot of rotation and there rotating with a LOT of force, your clutch isnt fully disengeging and that will make shifting difficult and wear out your synchros.

BC

 

I ran Mobil 1 in my 1998 C5 for about 50,000 miles (from 50,000 to 100,000 miles on odometer). At 100,000 miles I started to get a grinding going into 6th gear. Changed clutch fluid, no change. Then I changed trans fluid to Amsoil ATD, my grinding stopped immediately! No noise, now at 119,000 miles and still fine.

Bill Curlee is right on with his explanation.

BTW, GM changed to carbon blocker rings in 2001, so those years and later can use any synthetic fluid.

 

Both of these AMSOIL products use a Group IV PAO synthetic basestock and are recommended by AMSOIL for the C5 manual tranny:
AMSOIL ATF (product code ATFQT)
AMSOIL Torque-Drive Synthetic Transmission Fluid (product code ATD1G)

Although I have been using the ATF in my 02 Z06 track car for years and my CTS-V daily driver for about 6k miles now, I've recently learned that the ATD is more shear stable (actually is totally shear stable as it has no viscosity modifiers) and is thus my current recommendation for the C5 manual tranny. The ATF is very shear stable, much more so than the vast majority of Dexron III fluids on the market and has worked well for me in both of my cars, but given the demands our tranny places on the fluid, I think the ATD is the better of two good choices.

 

sounds like syncros are bad

 

SEE! I told you he would set you straight on the good stuff!

marcussmith28 I agree that the synchros/blocker rings are probably not as good as they should BUT, changing the old nasty fluid or just up grading the dino ATF to the right synethic fluid will usually cure the problem and allow you to not have to rebuild the tranny for a long time.

IF, you continue to drive it the way it is, you will cause synchro and blocker damage much worse than it already is and then you will need a rebuild.

 

You guys are great! Everyone had excellent suggestions for checking out the potential causes (clutch and fluids) with detailed procedures and products to use. I couldn't ask for more! I won't be able to get it up on a lift for a few weeks but I can get the fluids and now I have a plan. Many thanks to vettergt8, Oldvetter, Subdriver, marcussmith, and Bill Curleee! Happy New Year!

 

Couldn't agree more for all of them. I didn't know all that about the Amsoil ATD though. Good stuff.

BTW, you get water in your fluids over time. One reason plus those fluids don't live forever. Not as they're designed to work anyway.

 

I have a 1998 Coupe with the same problems you are experiencing. A fluid change to Schaeffer's ATF cured many of the symptoms, however I will remove the transmission and re-build it since inferior synchros, shifter fork, and shifter keys were used. Try a fluid change first, it is the cheapest route to go.

 

As suggested by "subdriver" and others, I changed the transmission fluid with AMSOIL Torque Drive (ATD1G) fluid a couple of days ago and also the clutch fluid with DOT4 brake fluid. It made a huge difference in shifting in first and second gears. I gave it a good test today and had no problems in 110 miles of non-highway driving. The change was immediate but I didn't want to get too excited about it until I had put some miles and lots of shifts on it. It never popped-out of first or grind going into second. The fifth to sixth sometimes requires a little finese to keep from a momentary grind but that also seems better.

So I'm hoping that this is a long-term solution to my long-term problem. There may still be underlying synchros issues but this new fluid seems to have overcome the shifting problems for now...or at least has bought me more time. The last fluid change was 30,000 miles ago using standard GM ATF and it had a foul smell when drained. That would seem to prove the need for better synthetic fluids like the AMSOIL recommended. I don't think that I had a clutch problem but changing the fluid at 59,000 miles was a good idea anyway.

Thanks again for all the input and suggestions. Hopefully, this will help others with similar shifting problems.