Hopefully finishing up this weekend and need to add gear oil to the tranny. Any recommendations for gear oil. I'm assuming like an 80/90 but need advice. Also regular dino or synthetic?
Thanks in advance!

This topic is a hot one on here. We use regular ole' 90 weight gear oil in ours.

#1 tip: DON'T use a GL-5 lube (and most of them are)...Use a GL-4!!!

I like Redline's synthetic offerings; MTL, MT-90 etc. Other good ones are Pennzoil Synchromesh and Amsoil lubes.

Back in the day..

The factory suggested ATF for shifting.
I liked 90w but would mix in ATF in the colder months to help shifting.

Good news is Jamie Passon (Passon Performance) has a proprietary fluid he sells specifically for our old Mopars.

I haven't tried it yet but I haven't heard anything bad about it.

PENNZOIL SYNCHROMESH works great !!!

Straight ATF, I used in many NP833 on the street and at the track on drag race only Hemi cars So did the many of the new car Mopar factorys

As mentioned above, you don't really want to use a GL-5 gear lube in a synchronized transmission.

The reason is that all GL-5s contain Extreme Pressure (EP) additives. They chemically react with the surfaces of the metal parts and form oxide layers that are a last ditch defense against metal-to-metal contact. This is especially important in automotive rear drive axles. The hypoid gearing requires some sort of EP because of the rubbing, sliding contact. I believe EP gear oils were the result of or made necessary by hypoid gearing.

The EP additive package therefore is by nature corrosive. If all the parts are ferrous, that is no problem. But if there are copper alloys the additive package attacks them too and maybe preferentially to ferrous metals. Your synchronizers are a copper alloy and they act as brakes, relying on friction. EP additives attack the synchronizers and the resultant surface film of oxides reduces the synchronizer's abilities.

Sure, millions of standard transmissions are in use with a GL-5 oil, I own at least four. BUT use of a GL-4 fluid will make shifting better in almost every (transmission) case.

R.

The factory acknowledged that ATF was harder on some 4spd parts over a period of time and recommended gear oil for some conditions/applications.

If you will be doing a lot of cold weather driving, the lighter fluids like ATF can help shifting... but I'll guess you aren't and agree they aren't the best for durability. Some of the newer ATF formulations are really hard on syncros.

OK would be regular 80W90 or 75W90. Better would be GL4 80W90. I have found shifting is noticably better with the specialized synthetic lubes. I have used and would recommend Redline "MT90". Its a full synthetic multi-visocosity manual transmission lube. I get it from Summit. I'm sure the Passon lube is similar and works well; I just haven't used it.

If you really need a lighter fluid, "Sycromesh" will be similar to ATF but with an additive package designed for manual transmissions. Its used in modern MT's and available at most parts stores. My local Autozone usually keeps a few quarts on hand. The lower viscosity Redline MTL would be good also. Similar to the "MT90" but lower viscosity.

I used Passon's in 2 different A-833 transmissions and noticed a marked improvement in operation.

Just my

Good Luck.

Frank

Thanks again!

back in the day the tranny place I used put 50% 30W oil and 50% ATF in.