New clutch...Noise when clutch is not depressed and trans in N?

May 7, 20204 yr

16 hours ago, ETI4K said:

What was the most commonly reported need for the rebuild(s)?

Were you ever able to do a before and after comparison?

The first two refreshes were for a serious grind going from first to second and a a mild grind going from second to third. Two others were bearing noise only. Complete success on all of them. Here's a thought. The first trans Was for the snick when changing gears. The synchros I removed looked near pristine. I reused them later in another trans. The shotgun refresh fixed the original problem but when I used the old synchros (near pristine) in a later refresh they too fixed the shifting problem. WTF, said I. Skip to years later when there was a discussion here about gear oil. Some brands work much better, shifting wise and I'm assuming it could affect bearing noise too. I wonder if a gear oil change would improve things? @Zup highly recommends A/C Delco Friction Modified. I now wonder if my first trans with the shifting problem had really been fixed with a different gear oil. Back then I probably used a Kendall product.

Edited May 7, 20204 yr by Mark Maras
Old age.

Link to comment

https://www.classiczcars.com/forums/topic/63959-new-clutchnoise-when-clutch-is-not-depressed-and-trans-in-n/?&page=3#findComment-599025

Share on other sites

Remove Ads

May 7, 20204 yr

comment_599032

Hmm, interesting. I know the friction modifiers work well for their intended purpose, especially when the machine was designed for their specific use. If used in a trans (I'm guessing that was not originally designed for it), would their be a chance that, for example, the synchro rings would become "too slippery" and you could get the grind back?

Link to comment

https://www.classiczcars.com/forums/topic/63959-new-clutchnoise-when-clutch-is-not-depressed-and-trans-in-n/?&page=3#findComment-599032

Share on other sites

May 7, 20204 yr

comment_599036

I haven't tried ACDelco friction modified myself but it is highly recommended for old Z transmissions. I'm curious if an oil change to a different product will quiet the bearing down if it's in the trans?

Link to comment

https://www.classiczcars.com/forums/topic/63959-new-clutchnoise-when-clutch-is-not-depressed-and-trans-in-n/?&page=3#findComment-599036

Share on other sites

May 7, 20204 yr

comment_599037

3 hours ago, ETI4K said:

Hmm, interesting. I know the friction modifiers work well for their intended purpose, especially when the machine was designed for their specific use. If used in a trans (I'm guessing that was not originally designed for it), would their be a chance that, for example, the synchro rings would become "too slippery" and you could get the grind back?

The question of the definition of "friction modified" has come up before. The label doesn't say "modifier" it says modified. So, not the same as friction modifier for a clutch type limited slip differential, which is modifying the slippage between clutch discs, not synchro rings. Besides that "modified" just means different. It doesn't really say which way or how the modification is happening.

But, besides all that, and what "friction modified" actually means it just boils down to the fact that people have tried it and compared it to the "normal" transmission oils and it works a lot better in removing the poor synchro perfromance. Redline MT90, Synchromesh, and Synchromesh Friction-modified all work very well. Also, Swepco 201 blended with ATF works very well also. Better than Valvoline 80W-90 manual transmission fluid.

I don't think that anyone really knows exactly why one works better than another. It's magic.