Ive been searching around for transmission fluid for the tranny in my truck. I bought the Ford work shop manual and it labels ESP-M2C83-C or ESW-M2C83-B as specs for the fluid. However, I haven't been able to find that specification on any transmission fluid in local auto parts where I live. The identification tag on the transmission has RUG-CD and from what I have read is that it is not a performance toploader.

 

Generally, 70's transmissions are happy with 90 weight gear lube (or 80W90 or 75W90). The older GL4 spec is better than GL5 for transmissions. GL5 has more extreme pressure additives for rear end applications which may not play well with the syncros in the transmission.

 

Thanks. That definitely helps

 

In my experience, GM Synchromesh fluid has worked great in all my manual transmissions. I know it is blasphemy to put that in a Ford, but the stuff works.

 

80W90 for the tranys that era and older .

 

Thanks I'm going to go with Brad Penn Multipurpose Classic GL-4 Gear Oil

Brad Penn Multipurpose Classic GL-4 Gear Oil 023-7729 - Free Shipping on Orders Over $99 at Summit Racing

 

The 80w-90 GL-5 will eat syncros due to the sulfur but, typically the trans will need a rebuild by the time that shows noticeable effects. I run a bottle of the mt-1 and top off with 50w,engine oil.

 

Alex is pointing out an important issue. I don't remember which is which, but I researched it a long time ago, and one of the gear oils is not acceptable for brass. Make sure you find out which one and don't use it. IMHO, your manual transmission is precious. Take care of it.

 

Yeah I went back to check on what Alex mentioned and the Brad Penn product mentions that it is intended for those metals.

"This Brad Penn multipurpose Classic GL-4 gear oil is specially blended using high-quality Penn Grade mineral base stocks and select additive technologies. It is designed to be used with yellow metallurgy (brass, bronze, copper) and other soft metals used in synchronizers, bushings, thrust washers, and other components typically found in classic manual transmissions and transaxles."

 

Have a 91' 306 with T5 I did the same and yeah it actually improved the shifting way better than expected. Have you or anyone else tried synchromesh in the NP435 and/or other manual trans?

 

That's what I was referring to. The MT-1 is listed for GM and certain Chrysler manuals. I run a mixture of mt-1 and 50w in my T-18 and it shifts better than 80w-90. That said, 50w and 80w-90 have similar viscosities so the splash lubrication is sufficient.

 

I have used the GM Synchromesh in a couple 90's Honda 5 speeds and have checked with a heavy truck mechanic about it's use in a Ford F-700 tandem truck and he said it should be good for pretty much any manual transmission as it is an exteme high pressure lubricant. I think he said it's similar to a 50 weight oil...

It was a night and day difference in the Hondas, much smoother shifting and a lot less noise from the transmission.

 

In general, the lighter lubes will help a '70's transmission shift easier... but if run hard and hot the thinner viscosity won't protect as well causing early failure.

A really nice lube is Redline MT90. It is a full synthetic formulated for transmissions which acts like 90 weight at operating temp. This would work well in the OP's case... but also expensive, hard to find and overkill. The GL4 90 weight should work fine.