90/160 gearlube

[PontiacJoe]

My 35 Pontiac calls for 90 wt winter, 160 wt summer in the transmission. Can I use 85/140 Synchro lube without problems? I have read that GM Synchro Transmission Fluid may help my occaisional 2nd gear synchro clash. Pulling the trans for rebuild is a genuine PITA. If I can't find an easy fix, I'll just keep double clutching. Thanks for any comments and advice.
Joe

 

[mechtech2]

I am wondering if you even have synchros in that transmission?

Lubes are very much better than 75 years ago.

The 85-140 or similar would be my first choice, and a very good one.
The modern light trans oils are great, but for that transmission, a bit too light. You have other concerns than just shifting.

BTW, I'll give you $10.00 more than the original price of the car, and it will now be my problem! That should come out to [$650.00 or so.]

 

[PontiacJoe]

Thanks for your generous offer, but I don't want to take advantage of you, so I'll decline. 2nd and 3rd had synchro cups, and my 2nd has gotten a little slow. I understand the GM fluid has a friction enhancer that will help the yellow metal shoulder and cup "hook up" a bit more aggressively. I guess I'll try it and see. Thanks, I'll post results as soon as I get it done.
Joe

 

[mechtech2]

For best 'bite', a dedicated manual transmission fluid with friction modification specially for synchros is a smart choice.
But worn parts are possible, and no fluid will help.
And thicker oils impede quick synchro function.

What's gonna work best? In this case, you'll have to try and see.
but lean towards heavier lubes for protection in that old box.