4-speed gear oil? (1 Viewer)

[Freeborn]

I have a rebuilt 4-speed tranny about to back into my ‘78. I’m looking for input on what oil to put in it.

- FSM says 90 weight
- I can get non-synthetic 80w90, but it says it can’t be used with synchros
- Or I can get 75w90 synthetic that is synchro-safe.

So...What’s the best course of action?

 

[Stumpalama]

Anything in the 80-90 (80w-90 or 75W-90) weight is fine, IMHO. I've been running CAT 80W-90 gear oil in my H42 and Orion t-case for the past 12-13 years with zero issues.

 

[BRShap]

Does anyone have the latest info on GL4 vs GL5? I read early GL5 formulas would eat yellow metal (brass/bronze) and shouldn't be used in transmissions, only diffs, but the latest ones are safe?

GL4 has proven a bit hard to find at the local FLAPS.

 

[WarDamnEagle]

Red Line Synthetic Oil. Gear Oil for Manual Transmissions

Gear Oil for Manual Transmissions

www.redlineoil.com

 

[BRShap]

Red Line Synthetic Oil. Gear Oil for Manual Transmissions

Gear Oil for Manual Transmissions

www.redlineoil.com

72 bucks a gallon!

Is this necessary or is modern GL5 ok?

 

[Freeborn]

^^ That's what I was thinking when I saw the price, although I'm not sure I paid any less for the synthetic stuff I grabbed.

RE: Modern GL5, I was originally going to get Valvoline 80W-90 High Performance Conventional Gear Oil. It has "GL4" and "GL5" on the bottle. But then it also had a very prominent warning not to use with synchros. Hence, this thread.

 

[Splangy]

Brad Penn GL-4 is a reasonably priced GL-4

 

[GA Architect]

> CRC GL-4 < 5 gallons worth

 

[thebigredrocker]

I bought Sta-lube GL4 at Napa a year ago. A few years ago Carquest had GL4 in jugs labeled under the Carquest brand.

GL5 is specifically better EP gear tooth lubricant. Since the T-case and diffs have large gears that are always under load, they need GL5. The transmission has no gear load in 4th gear, so vegetable oil would prolly suffice in there on the highway.

I keed, I keed.

GL4 is specified for the trans because it has brass synchro rings. I've never actually seen any accelerated wear of HD brass syncro rings due to GL5 usage. Yes, GL5 is unkind to wimpy little syncro rings in T5 trannies or subaru boxes, but Cruisers seem to be too big & stoopid to care.

 

[WarDamnEagle]

From the FAQ:

Transmission: All SAE 90 Weight
Three Speed: 3.6 Pints
Four Speed: 6.6 Pints
Transfer Case: 3.6 Pints
Transfer Casew/ PTO: 4.4 Pints
PTO Winch: 1.2 Pints

It’s not like you need several gallons. $72 is what, dinner for a family of 4 at 5 Guys if you split a large fry?

 

[S4Cruiser]

I bought Sta-lube GL4 at Napa a year ago. A few years ago Carquest had GL4 in jugs labeled under the Carquest brand.
View attachment 1936717

Use the same and conveniently available from the Amazon.

Amazon product ASIN B000M8RYMC

 

[Stumpalama]

I bought a 5gal pail of Lucas 75W-90 for my 4Runner and Tundra. It seems it also meets the requirements for use with synchros (GL-4) and no warning on the label.

 

[Stumpalama]

I bought a 5gal pail of Lucas 75W-90 for my 4Runner and Tundra. It seems it also meets the requirements for use with synchros (GL-4) and no warning on the label.
View attachment 1937114

So, this thread inspired me to look into this GL-4 GL-5 issue and subsequently consider replacing my transmission gear oil.

 

[vpatsears]

I use the Red Line MT-90, GL-4.

 

[Coolerman]

I can tell you the horror story about my 1991 Pathfinder that had to have the tranny rebuilt because a Nissan DEALER put GL5 tranmission fluid in it during a flush and fill instead of the GL4 that the Nissan factory called for. How do I know they did it? They put on the receipt 5 qts of GL5 oil AND they gave me the remainder of the 5th bottle for topping off! I had no idea there was a difference at the time...

Right after I had the fluid changed, I towed a pop-up camper out to Colorado for vacation. By the time I got there the tranny was getting hard to shift. I took it to a local dealer out there and explained I had just had the fluid changed. They drained the tranny and showed a sample to me. It was full of brass bits! He asked if I knew what oil they used and I showed them the receipt and the bottle. He then explained what had happened. They documented it, drained the GL5 out and refilled with GL4, told me to try to get it home and take it back to my local dealer. I did just that. They fought me on it, but in the end they paid to have it rebuilt!

 

[MoCoNative]

I have personally run AmsOil for 20 years and over 350,000 miles in my 4 Toyotas. Never had any problems with it, run it out to 90,000 miles between changes, but I don't ever get in water. Its a little pricey but works great in a 40. I think all the 80/90 is GL-4 still. My Dad started running it in my 40 over 30 years ago and had the same results I have, long good life and it really helps with cold weather performance as far as shifting and turning and such in an old 40. Of course I have seen -30F below, and conventional 90 is so thick you can barely move the shifter sometimes.

 

[redv8tbifj40]

I use Mobil 1 Synthetic 75/90 in all the boxes and manual transmission.

Mobil 1 75/90 Synthetic Gear Oil

I buy it at Advance at the link above with an online order and pick up in store. I use coupon code RMN25 and save 25% so it's just over $10 plus tax/qt.

 

[GA Architect]

Anyone used the Driven Gear Oil?

 

[Freeborn]

After a lot of research and phone calls and recommendations I’m going to give the Royal Purple Gear Max 75w90 a shot. It’s what was originally recommended by the guy that rebuilt the transmission. I called Royal Purple and talked with a guy that spoke specifically to the differences in GL4 and GL5, synchros, etc. When I told him I had a ‘78 LC he said the Gear Max would work fine. Will report back...hopefully with good news.

 

[stoshzack]

Red Line Synthetic Oil. Gear Oil for Manual Transmissions

Gear Oil for Manual Transmissions

www.redlineoil.com

Redline is expensive, but good stuff. I use it in all my vehicles if applicable