C2 shifting problems and ? solution

[john pickens]

My 1965 327/350 4 speed has always had a "tight" gearbox but seems that second
gear is now becoming a problem. Often very hard to get into second especially
when cold. Sometimes requires double clutching. Seems equally difficult up or
downshifting. I have not identified tranny by number yet; not sure if posi but
I think is rebuilt original.
Transmission repair shop owner suggests that may be possible and safe to change gear oil to less viscous gear oil or even combination of several to ease the
shifting. Assuming the present gear oil is original type in sufficient amount,
any thoughts on such a plan?

[Duke W.]

Re: C2 shifting problems and ? solution

The lubricant specification for the Corvette four-speed is Mil-Spec 2105, which is equivalent to SAE 80W-90 GL-5 gear oil.

A synthetic GL-5 such as Redline 75W-90 NS may provide for easier shifting especially at cold temperatures and may be worth trying. This 75W-90 is formulated WITHOUT a friction additive designed for limited slip differentials.

You mention "posi" in the context of the transmission, but positraction, which requires either a supplemental friction modifier or a lubricant pre-formulated with a friction modifier is only applicable to the differential.

I believe your '65 has the two holes in the transmission shift levers, which allow two different linkage ratios. In my experience the "fast ratio" makes for rather "notchy" and stiff shifting, and I would not recommend it. The actual speed you can shift at is more limited by how quickly you can actuate the clutch.

Duke

[Stephen L.]

Re: C2 shifting problems and ? solution

I have use STP as an additive in the trans to make shifting smoother and it works. Quantity: about 1/2 can.

[Richard S.]

Re: C2 shifting problems and ? solution

I have the same problem with the 4 speed in my 67. It's hard to get it to go into second and third gears...both up and down. I don't think it's related to the fluid type. If it's not the fluid, what adjustments could be tried to shift into second gear without the difficulties we are encountering? Thanks for any suggestions.

[Rich G.]

Re: C2 shifting problems and ? solution

For what it's worth when I got my 66 L79 in september it had those symptoms. First, although the clutch was new, the wrong throw out bearing was installed and a home made clutch rod was installed in order to make the clutch disengage (almost). We had to take the tranny out to fix the speedo drive gear and took the opportunity to put in the correct throw out bearing and clutch rod and also when refilling the tranny we put in the correct gear oil and 1 qt of Mobile One oil. The guy who works on my car swears by this. He has several C2's. The car now "shifts like butter".

I expect the clutch was never really disengaging. Can you shift without the clutch? Is it still hard to get into 2 and 3?

Rich Giannotti

[Craig S.]

Re: C2 shifting problems and ? solution

Likely culprits are clutch adjustment not allow complete disengagement, synchro wear, or the points made by others on lube...Craig

[Richard S.]

Re: C2 shifting problems and ? solution

Thanks for the help gentlemen. Let me try to explain the symptoms a little clearer and maybe that will help you to narrow things down. The shifting difficulties occur with or without clutch use. From neutral,finding first is difficult. The shifter always wants to go into third and it goes into third easily. If I lean left with the shifter it will often go into reverse rather than going into first. (I am using a Hurst linkage with a stock looking handle, where the reverse lockout function is inoperative.) Once the car is on it's way, it wants to go from first to fourth easily but will not drop from first to second without difficulty. Is it possible that only the linkage needs to be adjusted? What do you think?

[Craig S.]

Re: C2 shifting problems and ? solution

Rick - based on your new information, to me it sounds like you are dealing with shifter adjustment issues vs internal transmission problems. I happen to have a 66 project in the works now, it came with a Hurst shifter, however, I purchased a new reproduction midyear shifter from Michigan Corvettes (or something like that, they were at Bloomington last year). My shifter works correctly however, but I did notice that Hurst is a far tighter and notchier feel than the GM unit, I suspect it requires more precise adjustment to work correctly. I don't know how it's adjustment works, but I would assume it is similar to the GM process defined in the service manual. Good luck!...Craig