Transmission fluid

[saf98tj]

Hi guys
A few weeks back. I changed my transmission fluid. Recommended fluid is 75-90 GL3. Couldn't find any locally so I went to the dealer. They told me the part number changed to a 10w-30 motor oil. I had some dino 10w-30 oil already so that is what I used. I am finding it difficult to engage first gear when cold. Not sure if this is happening now because of the cold weather, oil or combination of both. This is the first cold weather season I have had with it so I am not sure if this is just due to the cold temp. It didn't seem to be a problem when I first changed the oil but it was warmer then.

Any thoughts? What fluid do you recommend?

[ASauer17]

Agreed, the 75W-90 GL-3 gear lube is the "right one" which can be added to the GL-4 with synthetic 10W-30 oil. Basically... 10w-30 is the same viscosity as a 75W-90 and its easier to find in the stores.

I've used Redline's MT-90 (75W-90 GL-4).

[schwalby]

Shifting my Jeep in the winter is stiffer too. It's a TJ thing.

[ASauer17]

hahah here's a stupid thought... in my old manual SUV, it was so hard to shift in the winter ALL because the accordion boot was TOO cold to move. I replaced it and it never happened again.

another idea: temp sensor

better yet... Mine shifts hard in the winter if I legit go out, start it, then drive without letting it warm up for atleast 4 minutes.

[ZAEDOCK]

My 1953 SM420 shifts fine with Coastal 75W90 GL3/GL4/GL5 rated oil, even when cold.

[Modeler]

I've been running the Royal Purple Synchromax for 70K miles so far in the 6spd. Never had an issue when shifting when it is cold out.

[nostaw]

Use 100% synthetic oil instead of conventional... Will not thicken up in the cold.

JW

[ZAEDOCK]

Every oil thickens when it's cold.

In the case of gear oil, the two specs typically used for measuring kinematic viscosity are 40*C and 100*C. They are measured in centistokes.

[nostaw]

Every oil thickens when it's cold.

In the case of gear oil, the two specs typically used for measuring kinematic viscosity are 40*C and 100*C. They are measured in centistokes.

True, but synthetics are more stable/will change less/flow better.

JW

[Posimoto]

A manual tranny doesn’t have the same heat strains as an engine, using synthetic in a manual gear box is a monetary waste.

[Modeler]

I disagree, synthetic "cured" a synchro issue with the 2-3 shift in the NVG370 which is a common problem.

[saf98tj]

I will try letting it warm up a bit and see what happens. Maybe try the redline oil as well.

[ZAEDOCK]

A manual tranny doesn’t have the same heat strains as an engine, using synthetic in a manual gear box is a monetary waste.

Novak Adapters mentions this, and in a Jeep application, I also agree.

I disagree, synthetic "cured" a synchro issue with the 2-3 shift in the NVG370 which is a common problem.

That probably had more to do with the additive package than the base oil used. When I used regular GL5-only 80W90 in my SM420, I had notchy shifting. When I switched to a GL3/4/5 rated oil (which uses a different add pack to attain both GL3/4 and GL5 at the same time) my shifting is awesome, even when below zero.


Todays conventional oils are very good with decent pour points. Many of the synthetic rated oils are still group III oils, so it's splitting hairs (conventional are typically group 2 or 2+). In a regular trail Jeep application conventional oils are fine. This is just my opinion though, as many people swear by PAO synthetics and that's cool with me. Amsoil, Redline, Royal Purple and several Mobil products are all nice oils. Synthetics are typically much better for extended drain intervals and extreme temperatures. They also hold up better under extreme use, even the GRP III oils, like racing and trail beating, although I think it applies more to engines than driveline with the trail beatings we typically dish out.

[Posimoto]

Coastal GL5 is safe for yellow metals but not all GL5 are built the same. Yellow metal friendly GL5’s have to pass the ASTM D130 test to qualify for MT-1 rating. Basically it’s a copper strip corrosion test to evaluate the corrosive tendencies of oils to copper containing materials.

If you have concerns with using GL5 with yellow metals Napa sell StaLube GL4 by the gallon (part number is SL24238).

[saf98tj]

Definitely a cold weather thing. Shifted smooth as butter yesterday in the warm weather.