Two questions on my 1938 66S

[Daves1940Buick56S]

I finally got the interior finished and have been driving it more. Now some of the more minor issues can be handled. 2 things I noticed:

 

1. After the trans is warm, I am getting "biting" on the 2nd and 3rd syncros as I shift in (especially on 3rd). Quiet when cold. Do I need heavier oil? I think I have 85W-90 in it now.

 

2. Sometimes when I let my foot off the gas I get soft popping out the exhaust. It did this on the old carb as well. Ideas?

 

Cheers, Dave

[MCHinson]

I would suggest you switch to MasterPro GL140 gear oil in the transmission. That solved all of the transmission issues with my 1937 Model 61. I also suspect you might have a small exhaust system leak somewhere. 

 

https://www.oreillyauto.com/detail/c/masterpro-chemicals/chemicals---fluids/maintenance-chemicals/grease---lube/gear-oil---additives/gear-oil---140w/587d6374459f/masterpro-chemicals-conventional-gear-oil/mp03/80040?q=gear+oil+-+140w&pos=0

[jenz38]

I run also a 140 grade oil, with the best results.

[C Carl]

This having been discussed from time to here, you will shift better if you DO NOT use an EP gear lube. Synchros depend upon a certain level of resistance, which EP will defeat to a certain degree. EP can also be corrosive to yellow metal. That includes the synchros. Become an expert at double clutching a synchromesh transmission, if you are not yet. Up and down. Beat the synchros, and it will feel like you are moving the shift lever through the air by comparison. The coordination to do this will be of great value when you drive a crashbox trans car from the ‘20s and earlier.    -    Carl. 

[MCHinson]

9 hours ago, C Carl said:

This having been discussed from time to here, you will shift better if you DO NOT use an EP gear lube. Synchros depend upon a certain level of resistance, which EP will defeat to a certain degree. EP can also be corrosive to yellow metal. That includes the synchros. Become an expert at double clutching a synchromesh transmission, if you are not yet. Up and down. Beat the synchros, and it will feel like you are moving the shift lever through the air by comparison. The coordination to do this will be of great value when you drive a crashbox trans car from the ‘20s and earlier.    -    Carl. 

There are some EP gear oils that are corrosive to yellow metals. Not all are. The Masterpro GL4 that I posted has worked well for me for many years. As a general rule GL3 and GL4 gear oils are typically safe for yellow metals. I would avoid any that are GL5 unless you check the specific technical sheets for them to confirm that they are safe for yellow metals. 

[Daves1940Buick56S]

Thanks for the replies! I do have StaLube 140 but it is GL-4. I have it in my 1940 with no issues, but that trans was completely overhauled with mostly new gears. I did find one example of 140 weight GL-1 that isn't only sold in 5 gal pails:

https://www.amazon.com/Millers-Oils-Green-non-additive-bottle/dp/B06ZYGFXF4

So I will order this and try it out.

 

On the not-so-good news front, I drove the 38 about 60 miles on Sat. It drove really well, but I do have an exhaust leak that got somewhat worse, as I expected. It almost sounds now like it may be under the hood, which would mean either donut or manifold gasket. 😬😬 More exploratory work to do, but my next task is to have the wheels stripped and redone. I am going to do them in Dante red and have the 3 silver stripes done. Should look awesome with the black car! Also I will put on the wider whitewall Lesters that I took off of the 40 last year. Wheels coming off tomorrow.