Gearbox oil

Id say no being RP says its a replacement for a trans that use ATF. If your gonna use 80/90 lube make sure its GL4 rated not the MT1 lubes the likes of autozone sells. I ran both 80/90 in my 91's ax5 and 10/30 synthetic and Id use nothing else but the 10/30 which jeep now recommends. If you live where its hot all the time the 80/90 lubes would be OK but shifting in my ax was near impossible in 20 degree weather.
 
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I use GL4 conventional by Driven brand from summit racing. Works well. Synchromax will work but it’s not the best choice. Even ATF will work but I wouldn’t choose it either.
 
About 10 years ago I called Royal Purple about the GL 4/5 debate and they reassured me their proprietary formula will work. Much of what you read in comparison test comes from the competition. Also, most of any chemical reactions with soft metals occurs at temps approaching 500+ degrees which the gearbox will never see.
 
I use 10W40 usually, in both my AX5 and my old T90 CJ2 transmission. GL4 is getting pricey and harder to find. There are a few tractor gear box fluids that are supposed to be good to go and much cheaper than GL4 gear oil. But 10w40 works as well. I do shorten the change interval a bit just for peace of mind since engine oil isn't as resistant to shearing as gear oil typically.
 
Gilaguy23 said:
Id say no being RP says its a replacement for a trans that use ATF. If your gonna use 80/90 lube make sure its GL4 rated not the MT1 lubes the likes of autozone sells. I ran both 80/90 in my 91's ax5 and 10/30 synthetic and Id use nothing else but the 10/30 which jeep now recommends. If you live where its hot all the time the 80/90 lubes would be OK but shifting in my ax was near impossible in 20 degree weather.
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Thanks 10/30 it is great forum thank you peeps
 
Gilaguy23 said:
Summit racing and Jegs both sell 2 or 3 brands of GL4 manual trans specific gear oils and last time I bought quarts they were $10.99 each IIRC.
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44+ dollars a gallon isn't my idea of affordable, espeically if you have multiple gearboxes that need it. STALUBE used to be my go to when I could get it for 20 or less dollars a gallon. Then one day their price doubled and it's now along the same lines as what you mentioned.

Carquest/Advance Auto sells a straight 90 weight gear lube that's GL4. I saw a tractor gearbox lube at Tractor Supply that was also 90 weight and listed as GL4 once.
 
Gilaguy23 said:
How often you changing lubes? If your worried about wasting money on a vehicle Id say off the jeep and buy a toyota. ;)
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Factory "B" service schedule, which is the severe duty schedule, calls for an 18k mile change. I do 12,000k on the YJ, and track the CJ2 via operating hours, The CJ2 isn't exactly a daily driver so it gets changed once a year. The XJ has an AW4 in it and I do a 10k change on that one, but the Autos have a 12k change interval under the B schedule. Dex/Merc is way cheap though, and it's faster than changing the engine oil on an AW4 to just do a basic fluid change.
 
Dang man, thats crazy overkill IMO. MFG'ers put that kind of maint schedule in the manual hoping your a dummy and take it to the dealer for a $300 a year major lube service. You doing a lot of water crossings and getting intrusion?
 
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Fluids have also greatly improved over the years since our owner manuals were written and most new Fluids will last over 50,000 miles in trucks with manual transmissions.
 
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Gilaguy23 said:
Dang man, thats crazy overkill IMO. MFG'ers put that kind of maint schedule in the manual hoping your a dummy and take it to the dealer for a $300 a year major lube service. You doing a lot of water crossings and getting intrusion?
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Well, I like to think that I'm not a dummy, but I was a Marine for a while and now a firefighter/paramedic. I'm not sure if eating crayons and running into burning houses is too smart.

I use those schedules, both severe and "normal" as a baseline and adjust as I see fit or as my oil analysis suggests.

And yes, both these Jeeps see a lot of Off pavement use and water crossings in Oklahoma and Arkansas, with the XJ also doing duty as my daily driver. The CJ2 not as much as it's a big logistical operation to get it out of the local area lol.

Don't really have issues with intrusion, but it's not that expensive or hard to change out when you're not using 40 dollar a gallon lube. I also do regular lube analysis, which most people would consider wasteful, but I like having the historical data of what my oils are doing or any potential failing internal components before they fail, such as many hours from home.


Not my channel but I was on a trip with this guy and he got some shots of me. Both crossing resulted in 3 or 4 inches of water in the front floorboards.
 
thank you for your military service, and working in medical field, we always need both. at times i would buy gl4 at tractor supply and it worked fine. due to the fact that you do analysis i would say that you are a better judge then most. drive safety and enjoy you jeep.
 
Funny, we mentioned water intrusion. I did a fluid change on the AX5 today, had obvious water contamination. A gallon of Shell 10W30 and she's good to go. Might have been left over water from when I power washed this salvage trans before install.
 
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