How difficult is changing transmission, differential, and transfer case oil?

[Bilskirnir3124]

Hey all,

I have a 1997 Cherokee Sport 4x4 with a manual transmission and the 4.0L. I believe it to have stock differentials and an AX15 transmission, though I'm the third owner, and I know that one of the previous owners put a small lift on it so this may not be the case though I don't know how to identify them. I know it has the New Process NP231 transfer case as it just has 4Hi not 4 Part Time and 4 Full Time on the transfer case selector.

I'm planning on changing the oil on all of these components as well as lubricating the drive train components behind the transmission (I.E. any U-Joints/Double-Cardans) that have grease needles. How difficult a job is this, what oils and greases will I need, and what additional tools will I need beyond a funnel and a grease gun? I've done oil changes and some easy part replacements before, but beyond that my only guidance is a Haynes service manual. Figured I'd come ask people who have done this before what I'd be expecting and what best practices are. My local garage wants about $630 for the job. Thinking I might be better off doing it myself.

Thanks for the tips.

 

[RCP Phx]

A funnel is pretty useless, either buy the squeeze bag lubes or pump style dispensers.

 

[Anak]

The #1 thing to know about changing the oil in the AX-15 is that you do NOT want the oil the auto parts store is going to offer you. They will offer you GL-5. GL-5 is not compatible with yellow metal. IOW, it will destroy your synchros. Unless you want a good reason to rebuild your transmission, don't get your oil from the auto parts store. Order it from someplace like Summit or get it from an Amsoil dealer who knows what he is selling.

Here is my write-up for what I do when servicing the AX-15 in my '96: AX-15 oil change and shifter bushings

As to the NP231, you probably want ATF for that one. Drain it from the drain plug, fill it up to the top of the fill plug.

Differential(s) won't have a drain plug. Remove all the bolts except for the one at top center. Just loosen that one bolt a couple turns. The carefully pry the base of the diff cover away from the pumpkin. You should get a sheet of oil draining out, but as long as you leave that top bolt you won't drop the cover in the drain pan. Once it has slowed down you can then carefully remove the top bolt and release the cover into your other hand, skipping the making of a big mess. Wipe the inside of the cover clean with paper towels and brake cleaner. I like the lube-locker gaskets. I have been reusing mine (D44/D30) for years. No issues. Seal things back up and refill to the top of the fill plug.

It will be much cheaper to do it yourself than to pay a shop.

I do recommend the oil in bags. It is much easier to refill the differentials from a flexible bag. Amsoil is one source, I am sure there are others. I keep the empty bags--carry one in your rig in case of need on the trail.

 

[RCP Phx]

The #1 thing to know about changing the oil in the AX-15 is that you do NOT want the oil the auto parts store is going to offer you. They will offer you GL-5. GL-5 is not compatible with yellow metal. IOW, it will destroy your synchros. Unless you want a good reason to rebuild your transmission, don't get your oil from the auto parts store. Order it from someplace like Summit or get it from an Amsoil dealer who knows what he is selling.

Here is my write-up for what I do when servicing the AX-15 in my '96: AX-15 oil change and shifter bushings

As to the NP231, you probably want ATF for that one. Drain it from the drain plug, fill it up to the top of the fill plug.

Differential(s) won't have a drain plug. Remove all the bolts except for the one at top center. Just loosen that one bolt a couple turns. The carefully pry the base of the diff cover away from the pumpkin. You should get a sheet of oil draining out, but as long as you leave that top bolt you won't drop the cover in the drain pan. Once it has slowed down you can then carefully remove the top bolt and release the cover into your other hand, skipping the making of a big mess. Wipe the inside of the cover clean with paper towels and brake cleaner. I like the lube-locker gaskets. I have been reusing mine (D44/D30) for years. No issues. Seal things back up and refill to the top of the fill plug.

It will be much cheaper to do it yourself than to pay a shop.

I do recommend the oil in bags. It is much easier to refill the differentials from a flexible bag. Amsoil is one source, I am sure there are others. I keep the empty bags--carry one in your rig in case of need on the trail.

X2 on the LubeLocker gaskets

 

[Rob Mayercik]

X3 on the lubelockers - best way to fly.

The last time I changed my rear diff oil, I didn't have the oil "bag" (had a couple of the bottles still in the garage, so used what I had) - I took a short piece of vacuum hose (just a couple inches) and stuck it on the little nozzle cap, that gave me similar flexibility to get the stuff into the pumpkin as what the bags do, and I didn't have to buy anything.

Someone on here replaced the top-most bolts on their diffs with studs and nuts, to provide a permanent "hanger" for the cover and make reinstallation easy - one of these days I may well do that myself, since I have aftermarket diff covers that are a lot heaver than the stock ones.

ATF is the specified fluid for the transfer case. ALWAYS make sure you can get the fill (upper) plug open before you mess with the drain (lower) plug on the tcase. If the trans is set up the same way, same rule applies.

 

[Bilskirnir3124]

The #1 thing to know about changing the oil in the AX-15 is that you do NOT want the oil the auto parts store is going to offer you. They will offer you GL-5. GL-5 is not compatible with yellow metal. IOW, it will destroy your synchros. Unless you want a good reason to rebuild your transmission, don't get your oil from the auto parts store. Order it from someplace like Summit or get it from an Amsoil dealer who knows what he is selling.

Here is my write-up for what I do when servicing the AX-15 in my '96: AX-15 oil change and shifter bushings

Nice write up. I'm probably going to try to do the oil change from the bottom simply because I don't have boots for the shifter assembly, and I plan to later do a short shifter replacement. I think the previous owner put a TJ shifter in this particular XJ. The shifter seems longer than what I usually see. And thanks for the tip on the yellow metals and its incompatibility with standard GL-5. I didn't see a mention of it in either manual I have. Do you have a brand of 75w-90 and/or an additive/friction modifier you recommend to please the Synchromesh gods?

As to the NP231, you probably want ATF for that one. Drain it from the drain plug, fill it up to the top of the fill plug.

For this application I assume any reputable brand of Dexron III will do?

Differential(s) won't have a drain plug. Remove all the bolts except for the one at top center. Just loosen that one bolt a couple turns. The carefully pry the base of the diff cover away from the pumpkin. You should get a sheet of oil draining out, but as long as you leave that top bolt you won't drop the cover in the drain pan. Once it has slowed down you can then carefully remove the top bolt and release the cover into your other hand, skipping the making of a big mess. Wipe the inside of the cover clean with paper towels and brake cleaner. I like the lube-locker gaskets. I have been reusing mine (D44/D30) for years. No issues. Seal things back up and refill to the top of the fill plug.

Awesome. Looking below I can see I'm grabbing a set of Lube-Locker gaskets with the oils. I can see in the manual that the front diff takes 75W-90 weight just like the transmission if you aren't towing (I don't foresee any regular towing my future). Now the Haynes manual specifies GL-5, but would it be acceptable to use the same type of oil as the transmission in the front diff? As for my rear diff, my truck has a Class-I towing hitch. I would assume that that means I need to get an API GL-5 80W-140?

As far as chassis/drive-train lube goes, I have some Lucas Red 'n Tacky grease. Will that be sufficient for the job?

Sorry about all of the questions. This is just a lot of data to compile, and I want to make sure I have my ducks in a row.

 

[Anak]

For the transmission I run Redline MTL or MT-90. The Redline manual transmission oils have the reputation of being the best choice for an AX-15 as they seem to provide the smoothest shifting. Still not great shifting, but better than you will get with a different oil. Amsoil is the only other alternative I would consider. I do not run any additives in the transmission.

Yes, any reputable brand of Dexron III should be fine for the NP231.

Do not use the same type of oil in the differentials as you use in the transmission. The auto parts stores do have oil for the differential (that is generally all they have in terms of gear oil). If you have no plans for towing and you do not plan on wheeling it hard (rocks, waterfalls...) then do not bother with the heavier gear oil. You will get better mileage with the lighter oil.

I have no idea about the Lucas grease for the chassis. I run a Mobil1 synthetic. Look up the compatibility of the Lucas grease with other greases. Some greases are compatible with a wide range, others are not.

 

[Bilskirnir3124]

Awesome. That takes care of most of it then. Thanks.

I have no idea about the Lucas grease for the chassis. I run a Mobil1 synthetic. Look up the compatibility of the Lucas grease with other greases. Some greases are compatible with a wide range, others are not.

Red 'N Tacky is an NLGI #2 Lithium Complex grease. It appears to be compatible with a fair amount of other greases, but I have no idea if the problem greases in this chart are likely to be in my U-Joints and stuff.

This might be something better left to a pro? Or maybe I'm just overthinking it?

 

[RCP Phx]

Awesome. That takes care of most of it then. Thanks.

Red 'N Tacky is an NLGI #2 Lithium Complex grease. It appears to be compatible with a fair amount of other greases, but I have no idea if the problem greases in this chart are likely to be in my U-Joints and stuff.

This might be something better left to a pro? Or maybe I'm just overthinking it?

Your definitely over-thinking this........ I use this for almost everything I own https://www.amsoil.com/p/amsoil-100-synthetic-water-resistant-grease-gwr/

 

[Bilskirnir3124]

Your definitely over-thinking this........ I use this for almost everything I own https://www.amsoil.com/p/amsoil-100-synthetic-water-resistant-grease-gwr/

I am prone to overthinking things. That's for sure. So I should be good just to send it with the grease I have?

 

[Anak]

The problem greases sound relatively obscure to me: Barium, Clay, Polyurea and Sodium

I don't know where those greases are used, but my guess is they are specialized and not likely to be in your U-joints or Ball joints.

 

[Bilskirnir3124]

Fantastic. Thanks guys.

 

[Bilskirnir3124]

Small update. Just something that was funny and somewhat frustrating.
Turns out my XJ is a manual swap. It was probably an automatic at some point in the past. What I thought was an AX15 is actually an NV3550. Looking at pictures of the shifters it probably came from a TJ Wrangler, not a 2000s XJ. This does mean though that I don't have the tools to get into the transmission yet. Who thought that 17mm sets screw were a good fill and drain plugs?