Gear oil motor oil or ATF in tranny/transfer?

I use gl-4 80w in T18 and D18 they run hot. I have read where some run ATF or 30-50wt motor oil because it runs cooler and does it hurt the yellow metal any input would be helpful. Thanks

 

I dont know. I have always put straight 90w gear oil in my t-case, trans, and diffs.
I know about putting ATF in the power steering but never heard of ATF in the manual trans and case. I really don't know.

 

Certainly in CA you would not need a less viscous oil.

Why do you think your gears run excessively hot? If they are too hot, then there must be a source of friction in the transmission. The gears will make some heat, but it's normal - they won't be room temperature after a long drive.

 

:iagree: Use the correct required oil.

 

How hot is "hot"?

I got one of those laser aimed infrared temp guns from Harbor Freight to check my stuff after a good hot drive.

 

You can sort of guess at how hot the case is by how long you can touch it. At 50C (122F), you cannot comfortably keep your hand in contact with the case. At 60C (140F), you will get a burn from more than momentary contact. That's not a lot hotter than pavement on a hot day, and I'd expect that's well within the operating range of a transmission.

 

I'm not sure about up in Mass., but out here, the interior of your car in the sun is consistantly 150-155 degrees

 

I expect that's true, but there's a distinction.

My point was that what feels hot on the surface of an iron transmission and can burn your hand is not very hot on a comparative scale. If you touch the surface of an insulator (ie plastic) your skin immediately cools the surface of the plastic. Not so with a metal; the heat conducts to the surface faster than your skin and circulation can carry it away.

I've thought about this and discussed it before, in the context of iron core transformers. These operate in the range of 50-60C, and feel hot to the touch. But they aren't running hot in terms of relative temperature.

 

okay, I'm with you guys on the correct fluids but.....................I had both trans and tfrcase rebuilt and they still sound like they are rolling around on dry bearings!!!! whats the cure? is that normal?

Update.... bought a quart of that oil (lucas) you see on the counter in the plastic display with the crank and gears...supposed to help lube the engine.......put half in trans and half in trfrcase and all is quite...........should I expect it to explode any time soon?!?!?!?!

 

My work has an infrared gun I will try that maybe it just seems to hot to me. Thanks for the help and info.

 

Not at all, Lucas is good stuff.
I wonder about your oil levels though, if you had enough room to dump half a quart in both the transmission and transfer case. Gear oil should started dribbling out as soon as you pulled the fill plugs on both units.

 

Lubricant engineers design the oil to work without additives, changing the characteristics of the oil is not a good idea.

Check this out, lucas entraps air in the oil.... not good.
http://www.bobistheoilguy.com/images/lucas/lucas.htm

 

the trans, transfer case and axles need the cushioning of gear oil.
These old boxes can't handle ATF!
If you are running dino gear oil, 80-90 wt, try synethic (sp?) gear oil.
I got great results with mobile 1 gear oil. (I went with the heaver I think 140) in both my '61 and '74 CJ5.
Amsoil gear oil works great in my Harley trans, (it had a gear chatter that was horffic from day 1).
If the trans is growling away, it means that there is metal on metal.
Get rid of the fluid and go new gear oil and maybe a heavier weight to cushion those moving parts. ( When you dump it, use a CLEAN pan and check for a "metal shine" in the fluid as it comes out, or worse yet "Reeses Pieces" both are a B.A.D. sign.
If the noise is still there, bearing? gear? going south.
As for the heat, well you got gears whipping @ in there, you gonna create heat.
Synethic oil will reduce some of the heat, (slicker reduced friction), but you will have heat no matter what.
I have a friend that has a burn mark on his forearm from the casting marks from a Chevy 4 speed! He tried to reach down and grab the linkage and got "tattoed" That was 1973!
Just an old Jeep addicts thoughts!
Joe
My name is Joe and I drive a jeep

 

Good info, thanks for the link.

 

The oil starts to breakdown at 250 *F. If your below that your safe. My T14 will get up to 150-160 after a long drive, some of that from friction in the gearbox, and some i believe is conduction from the hot engine block.

Another note, these are OLD truck gearboxes they will make some noise in the lower gears.

 

One thing I think he should do is add a tachometer to his test set up to see just how many RPM's he's spinning the gears.
I admit though, I’ve pulled milky looking gear oil out of my transmission before. I used to think it was drawing moisture some how but now I know it’s the gear oil foaming.

 

Thanks again for all the info. I started reseaching the different gear oils quite a selection and I do have a tach on order.

 

been using lucas for YEARS(probably longer than some of you have been alive) never had any issues ....you can whip air into any liquid with enough speed. just my 2c