Shifting problems with 91 6sp
03-04-2005, 11:24 AM
#1
Heel & Toe
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Shifting problems with 91 6sp
I just purchased a 91 6 speed and having trouble shifting from 1st to second. Every other gear is real smooth. I know gm installed something to do with the light that comes on that says " 1st to 4th gear" on dash at various times. Is there something I can do or install or disable this device. Sometimes it will shift smoothly though from 1st to 2nd , It's not all the time. Does my rpms and shifting have something to do with this. I'm frustrated and in traffic is a pain too and could be dangerous as well.
Any help or advise would be much appreciated here.
Jack
Any help or advise would be much appreciated here.
Jack
03-04-2005, 12:24 PM
#2
Melting Slicks
The skip shift is part of the CAGS system installed on all 6 speed Vettes since 1989. It was installed to skirt the EPA/CAFE fuel requirements (get better mileage). If you can shift from 1 to 2 at any time, even when the light comes on on the dash, then the previous owner has already installed a CAGS bypass switch on the transmission. If the system were functioning, it would force you to go from 1 to 4 under low-speed, part throttle conditions (actually blocks out gate 2 and 3).
Depending on mileage and wear & tear, the syncros in the ZF 6 speed transmission start to wear down, resulting in harder shifting. Also, a poorly maintained hydraulic clutch system can also degrade the life of a ZF transmission. Typically, the life of a ZF 6 speed is around 80,000 - 100,000 miles; after that, it starts to wear out. Some preventative maintenance can prolong the life of the tranny, including:
Depending on mileage and wear & tear, the syncros in the ZF 6 speed transmission start to wear down, resulting in harder shifting. Also, a poorly maintained hydraulic clutch system can also degrade the life of a ZF transmission. Typically, the life of a ZF 6 speed is around 80,000 - 100,000 miles; after that, it starts to wear out. Some preventative maintenance can prolong the life of the tranny, including:
- Change the transmission fluid. Use the Castrol synthetic motor oil (BMW M3 engine oil), available at BMW dealers
- Replace leaky/old clutch hydraulic master and slave cylinders
- Replace clutch fluid
03-04-2005, 01:06 PM
#3
Team Owner
I agree to a point with what 94Vette has to say, but for a few details....
** The oil you want is the Castrol TWS 10-60 - you will need 3 litres.
** The ZF, especially a black tag, is gonna last much more than 100k. I have 133k on mine...
** Don't be too quick to replace the hydraulics. Make sure they are not leaking first. GM has had a problem with those parts for a while now... if yours are weapy, but still ok, don't take that plunge right yet. I would replace the clutch fluid with Valvoline Synpower Brake Fluid. Great stuff!
** Read the C4 Tech FAQ! It's a sticky in C4 Tech.
** The oil you want is the Castrol TWS 10-60 - you will need 3 litres.
** The ZF, especially a black tag, is gonna last much more than 100k. I have 133k on mine...
** Don't be too quick to replace the hydraulics. Make sure they are not leaking first. GM has had a problem with those parts for a while now... if yours are weapy, but still ok, don't take that plunge right yet. I would replace the clutch fluid with Valvoline Synpower Brake Fluid. Great stuff!
** Read the C4 Tech FAQ! It's a sticky in C4 Tech.
03-04-2005, 01:25 PM
#4
Melting Slicks
** The ZF, especially a black tag, is gonna last much more than 100k. I have 133k on mine...
), but I guess my point is that after this many miles, it starts to deteriorate unless properly maintained. FWIW, I have a "blue tag" ZF6, which is a remanufactured unit -- had it when I bought the car with 42,000 miles on it, and I have had no major problems other than a leaking rear tranny seal which was a $8 fix from NAPA
.