I just picked up my rebuilt w56 and the shop is telling me to use 10-30 oil instead of transmission oil. Something about better lubrication because some clearances are very small?? Mhh

 

Get it in writing on your warranty sheet and receipts.

Seems a bit squishy to me.

 

Use of motor oil in manual trannys is not unheard of.

There is little sliding force in tranny gearing, as there is much in hypoid gear differentials, thats why diffs require extreme pressure fortified oils, and trannies, not so much.

In fact, GL-5 gear oils are too slippery and the syncros in some transmissions won't operate effectively with them.

I ran straight 40 and straight 50 motor oils in the heavy duty New Process 435 in my '72 Ford truck. That tranny was still sound at over 250,000 miles.

My manual transmission Ford Escorts call for Dextron/Mercon ATF, an even lighter bodied oil. One has over 200,000 on it.

I would'nt be afraid to use the 10-30, especially on the specific advice of the rebuilder. After all, he is interested in a satisfied customer, and he does'nt want his work to come back.

Whatever lube you choose, change it out after a few hundred miles, and again after a couple thousand more.

All the chaff is generated in a fairly short time after the rebuild is put into service. After you get that out, the oil will stay clean and non-abrasive for a long time.

 

Sounds good, ive decided to do it and see how the shifting etc goes.
what I'm thinking also is given the bearings are this trany s weakness the 10-30 might help keep them lubricated a tad better?

 

Looked at this older thread and wondered how your tranny is doing.