I called the dealer to find out what transmission is in my truck. They only had a sales code, DDQ, which corresponds to the AX15 when I googled it. Anyone know if this is correct?

I was going to use the fluid capacity to figure it out, but they have no info on fluid capacity since the truck is so old. I didn't bother to ask about the rear axle since the guy just told me they have no fluid capacity info. So they can't tell me anything, basically. I saw an old post from 00DakDan about checking to see if Dodge recommends 75w-90 or 75w-140 in the rear diff. Since I can't find any help at the dealer, can you guys help?

Also, do I need to make sure there is friction modifier in either the AX15 (if that's what I have) or rear diff? I really appreciate it. You guys are awesome.

 

At least in 2000 Dodge recommends 75w-90 for the 9 1/4" (12 bolt cover) and 80w-90 for the 8 1/4" (10 bolt cover). If you don't have a limited slip differential then you don't need the friction modifier but it won't hurt it. I'd go with 75w-90 for either.

For the AX-15 it was a 75W90 Mopar 4897622aa.

 

Ok, so I'll check to see if I have a LSD. Got it. Probably going with Valvoline 75w-90, it's decently priced. Half of what M1 costs.

As far as the AX-15, is that the Mopar serial number that I will find on the housing somewhere? I googled the sales code that the dealer gave me, DDQ, and found this.

https://www.moparrepairconnection.co...ales-codes.pdf

It says that DDQ = AX-15. I will try to verify with the serial number if it's still visible when I get under there. No friction mod in the AX-15, right?

Huge help, thanks!

 

That's the Mopar part number for the oil.

 

Ok, got it. I did a little more poking around and read something about needing GL-3 rating OR GL-4, GL-5 with protection against soft yellow metal corrosion. Is it safe to use GL-5 Valvoline? I see that Royal Purple says it doesn't harm soft yellow metals. I don't wanna cause another problem while fixing this one.

 

It might not be easy to find a GL-3 oil. Yes, you need the soft metal protection. The problem is that without the "soft metal protection" the synchro's will get destroyed.

 

You can't use just any gear oil in the AX15, the additives that are in most of the new gear oils will destroy the syncro rings in the transmission. You have to use an gear oil specially formulated for manual transmissions, like Redline MTL. A cheaper option that is commonly recommend is 30 or 40 weight motor oil. I have been running 15w40 diesel oil in mine for the past year and it shifts great.

 

The superseded part number for the AX-15 is 4761839ad.

It's a 10w-30 motor oil.

 

That's crazy. Never heard of it before, but I only work on my own personal cars. Well, I believe that you guys know what you're talking about.

So I can buy any old 10w-30 from Autozone and use that? Gonna save me some money for sure. I was going to order $100 of Royal Purple and just use it in my trans and diff, but if I can use motor oil in my trans, I'll just buy Valvoline 75w-90 for my diff.

Just the thought of dumping motor oil in a transmission scares me tho, lol.