rear diff and manual trans oil

hwscowboy · Guru

rear diff and manual trans oil

jmont64 · Canadian Poncho Superstar!

That's what I use. Would be tempted to put synthetic in the tranny. I changed out a couple of my kids cars trannys to synthetic and made quite a difference especially in the winter.

Guru

DO NOT USE SYNTHETIC in 1949 trans just use 90 gear oil

427carl · A Poncho Legend!

694279 wrote:
DO NOT USE SYNTHETIC in 1949 trans just use 90 gear oil

Amen .

jmont64 · Canadian Poncho Superstar!

427carl wrote:
694279 wrote:
DO NOT USE SYNTHETIC in 1949 trans just use 90 gear oil
Amen .

Must be an obvious reason, fill me in.

norontcan · Canadian Poncho Superstar!

49 must be a manual tranny so straight gear oil should be fine.

When I acquired my low mileage automatic 65 CS I was looking to change out all the fluids. Called one of the major synthetic manufacturers to ask about switching over. He advised that if I was just doing a flush and fill then to avoid the synthetics. Said the old seals etc would probably leak as the synthetic would flow more. Said if I was doing a complete rebuild then synthetic would work just fine.

jmont64 · Canadian Poncho Superstar!

I'm not a proponent of synthetic oils at all but had heard of the difference in trannys so like I said I tried it in 2 of my kid's cars. Unbelievable difference, especially my youngest had a little Cavalier. Always was sort of a sticky shift and it instantly transformed it to silky smooth. In fact they are still running that little car in between Ottawa and Mount Tremblant every week. I'm hear to learn what the reasons are.

seventy2plus2 · Canadian Poncho Superstar!

Jerel, I suspect the little Cavalier is a somewhat newer vintage than a 1949, and henceforth ok to run synthetic. For the old school, especially with old seals, synthetic will become a large oil stain on the driveway.

jmont64 · Canadian Poncho Superstar!

Yeah I understand the obvious with old leaky seals and synthetic will leak out easier than standard oil but with replaced seals I wouldn't see an issue.

4SPEED427 · A Poncho Legend!

jmont64 wrote:

That's what I use. Would be tempted to put synthetic in the tranny. I changed out a couple of my kids cars trannys to synthetic and made quite a difference especially in the winter.

Someone who supposedly knows manual transmissions once told me that the syncro assemblies in the old units such as the 60's Muncies don't work well with synthetic. I haven't ever tried it to see if that's true but of course that won't apply to a 49 which I'm sure is not syncronized in any gear.

Taylor55 · Poncho Master!

I used synthetic in my old plow truck an early 80's 4 speed with bull low. It made it so much easier shifting gears in minus 20- and below temps. The tranny shifted with little effort but with the 80/90 gear oil at the low temps it was a chore to shift until the powertrain really warmed up. I still use gear oil in all the old vehicles as they are not used in cold temps.

Al

hwscowboy · Guru

I won't be driving it in the winter so not an issue.I will just go with the 90 w gear oil if I can find it,which is becoming an issue.First few auto parts stores looked at me like I was searching for the holy grail,lol

57 Pathfinder · Guru

A lot of newer oils are corrosive to the yellow metals used in the old synchro's. GL-4 or older is OK.

4SPEED427 · A Poncho Legend!

Your GM dealer can still sell you 80W90 if the parts stores can't help you.