WS6 GreeN

This mainshaft came out of a 99 Vette transmission. This is a pic of where the 5/6 cluster gear was. If I'm not mistaken, there's supposed to be splines all the way down this area? The gear just slid off without a press and it even moves a little on the shaft.

Jeremy@RPMTransmissions

iTrader: (12)

The 5/6 cluster gear is supposed to press onto the mainshaft. When you spend a lot of time accelerating in 5th and 6th gear you will eventually cause that gear to fret against the mainshaft and it will wear the press-fit area of the shaft out. This allows the gear to more slightly at the splines. Given enough time the 5/6 gear will wear through the splines on the mainshaft and you will lose 5th and 6th gear.

BMR Sales2

iTrader: (40)

Looks just like my old CTS-V mainshaft looked. Jeremy from RPM Transmissions has you covered.

WS6 GreeN

Jeremy helped me out a ton with ordering replacement parts and answering questions for me. I know who I'll be shopping with for my transmission needs fro now on...

Low N Slow

iTrader: (4)

Looks exactly like mine, replacing it fixed a high speed vibration I had chased for years.

SSCamaro99_3

iTrader: (1)

HOw much acceleration? Are we talking about just picking up a few mph on the highway while in 6th, or trying to accelerate from 60 to 100 in 6th? I would expect more out of 5th. It is a fairly useful gear in a 4.10 equipped car.

Jeremy@RPMTransmissions

iTrader: (12)

I mean lugging the engine down to 1300-1400rpm in 5th or 6th gear and then accelerating back up to speed without downshifting to 4th. That is very hard on the mainshaft.

mchdg86

iTrader: (3)

So running out 4th and going to 5th would be ok?

SSCamaro99_3

iTrader: (1)

Gotcha. Thank you.

Jeremy@RPMTransmissions

iTrader: (12)

WOT shifting into 5th gear is never a good idea. The stock 5th and 6th gear aren't strong enough to take a high RPM shift behind a high horsepower engine. If the car is less than 400hp it shouldn't hurt it. But if you are going to regularly shift into 5th gear I would recommend upgrading the 5th and 6th gear to a G-force gearset.

wrd1972

iTrader: (12)

Bingo.


More information on the issue here:
https://ls1tech.com/forums/manual-tr...vibration.html

The real reason for the issue is a shitty design in the way the 5/6 cluster gear fits the main shaft IMO. There is not enough "press fit area" built into the design to ensure good reliabilty. This is the reason it was redesigned for the 03 Cobras that have tighter fitting, individual 5 and 6 gears.