Differential gasket replacement questions

[Johnfromphilly]

You may or may not have seen my thread on deciding to buy a TJ and learning along the way how to do some work myself. I think I may have discovered an issue to jumpstart my first real project. I have done minor fixes to lights and the iginition cylinder etc but this is actual, under the jeep, don't mess it up, work.

Here are my two Differential covers, Dana 35 on rear and Dana 30 on front ( if I misidentified them please let me know). The rear seems to have a leak from the looks of the bottom of the cover (do you agree?). I have read up on this project and also watched multiple videos on how to do it. My biggest concern is that they both appear to have RTV as the sealant and I don't want to damage anything getting the surfaces clean.

Four questions:
1. should I even mess with the front as it looks clean? Maybe just extract old fluid and refill?
2. Do you agree the rear issue is a leak? Nothing on the ground under the Jeep. Should I still pull it and replace it?
3. Using lube locker gaskets is my plan, not RTV, good plan?
4. Should I replace the rubber plug on the rear or reuse the existing?

Rear Dana 35



Front Dana 30



Thanks for any input!

 

[Jerry Bransford]

You're correct on your front being a Dana 30 and rear being a Dana 35. The snap-in Dana 35 fill hole plug seldom gives problems so I wouldn't plan on replacing it.

The oil you see at the bottom of the Dana 35 cover could of course be coming from a leaking cover but that oil very well could be coming from a leaky pinion seal (which is somewhat common) on the other side of the axle where the driveshaft connects. I'd likely suspect a leaky pinion seal over a leaky differential cover. I'd clean up the bottom of the differential with brake cleaner, Simple Green, etc. and watch it over a couple weeks to determine where that seepage is coming from... the cover or the pinion seal.

Lube Locker gaskets are, generally speaking, easier and faster than using RTV to seal the covers. They work great most of the time, just not 100% of the time. I ended up having to use RTV for my front axle's differential cover. Despite my best efforts over a few months I couldn't get its Lube Locker gasket to seal drip-free and ended up using RTV to seal it.

 

[pc1p]

Some people will just pump their diff's down and refill with fluid. For me, I prefer to pop the cover and inspect the ring and pinion gears, spiders gears, etc. when servicing (especially with wheeling and hard use). It also gives a good opportunity to "flush" the differential out (with brake cleaner or suitable solvent) in cases of differentials with clutch-based limited slip differentials (or ones that may have sucked up some mud/water).

The cover is easy to remove - a putty knife helps if someone has really gooped the RTV on there. To reinstall - you can use RTV, a generic cork/rubber gasket, or spring for a reusable gasket like the LubeLocker. The LubeLockers are a tad pricey but I've had good luck finding them at a discount on Amazon (paid $10 for the Dana 30 and $14 for the Dana 44) - just check the "used" section. The advantage to them is that they're easy to remove and reinstall (I tend to drain my diffs ~12-18 months), especially on the trail if needed.

 

[Johnfromphilly]

You're correct on your front being a Dana 30 and rear being a Dana 35. The snap-in Dana 35 fill hole plug seldom gives problems I wouldn't plan on replacing it.

The oil you see at the bottom of the Dana 35 cover could of course be coming from a leaking cover but that oil very well could be coming from a leaky pinion seal (which is somewhat common) on the other side of the axle where the driveshaft connects. I'd likely suspect a leaky pinion seal over a leaky differential cover. I'd clean up the bottom of the differential with brake cleaner, Simple Green, etc. and watch it over a couple weeks to determine where that seepage is coming from... the cover or the pinion seal.

Lube Locker gaskets are, generally speaking, easier and faster than using RTV to seal the covers. They work great most of the time, just not 100% of the time. I ended up having to use RTV for my front axle's differential cover. Despite my best efforts over a few months I couldn't get its Lube Locker gasket to seal drip-free and ended up using RTV to seal it.

Thank Jerry, I will do that, makes sense that it may be the pinion seal. I will now be Googling pinion seal replacement also, haha.

 

[CodaMan]

It's most likely a leaking pinion seal as @Jerry Bransford mentioned, however it could have been replaced already and that person never cleaned it up. I would clean it up, check the fluid level and see if it's leaking. Replacing a pinion seal is not something I would do if it doesn't need to be replaced.

 

[Johnfromphilly]

It's most likely a leaking pinion seal as @Jerry Bransford mentioned, however it could have been replaced already and that person never cleaned it up. I would clean it up, check the fluid level and see if it's leaking. Replacing a pinion seal is not something I would do if it doesn't need to be replaced.

Thanks, I will be cleaning it today and we will see what happens. Unfortunately (or fortuantely) due to the weather here I am keeping it in the garage, the roads are wet and covered with salt. Will running it and moving in and out of the garage ( into reverse then back into 1st) expose the leak or would I really have to take it out for a "harder" ride? If so then the project can wait. I have not had a chance to treat the frame yet because of cold temps and outside water hoses are all turned off so I cannot rinse the frame down.

 

[Jerry Bransford]

Thanks, I will be cleaning it today and we will see what happens. Unfortunately (or fortuantely) due to the weather here I am keeping it in the garage, the roads are wet and covered with salt. Will running it and moving in and out of the garage ( into reverse then back into 1st) expose the leak or would I really have to take it out for a "harder" ride? If so then the project can wait. I have not had a chance to treat the frame yet because of cold temps and outside water hoses are all turned off so I cannot rinse the frame down.

Pinion seal leaks are normally fairly slow, I wouldn't expect it to show within a few minutes or even a few hours.

 

[Johnfromphilly]

Pinion seal leaks are normally fairly slow, I wouldn't expect it to show within a few minutes or even a few hours.

I may wait until Spring then once I can get dry weather and a chance to drive it consistently. It is going to the shop for PA inspection at some point so I will also have my mechanic check it out.

Thanks!

 

[Mobusaki]

This is a good first "under the Jeep" job for you to take on as you'll be changing, or at least checking, the diff fluid relatively often if you end up doing a lot of wheeling (Ventured into water or mud? Check the diff fluid). I would highly recommend you pull the covers since you have never laid eyes on the gears before. The last TJ I bought had broken spider gears in the rear and there was no indication of it until I pulled the cover off and saw the chunks.

I use the lube lockers now but used gasket maker for a while - either works fine, but I much prefer lube lockers for the ease of use and speed. By the way, gear oil smells awful, even when fresh. Have fun!

 

[Johnfromphilly]

This is a good first "under the Jeep" job for you to take on as you'll be changing, or at least checking, the diff fluid relatively often if you end up doing a lot of wheeling (Ventured into water or mud? Check the diff fluid). I would highly recommend you pull the covers since you have never laid eyes on the gears before. The last TJ I bought had broken spider gears in the rear and there was no indication of it until I pulled the cover off and saw the chunks.

I use the lube lockers now but used gasket maker for a while - either works fine, but I much prefer lube lockers for the ease of use and speed. By the way, gear oil smells awful, even when fresh. Have fun!

The PO did not take it off road I I do not plan on it myself, maybe a trail, maybe. I am now investigating the source of the leak. If it is the pinion seal as @Jerry Bransford and @CodaMan mentioned I may have a pro do it. I have reviewed that project and I do not think that is a good first project.

 

[MutantNinjaTJ]

The word "Major" is a bit of a stretch here but it's a good project to tackle for you. Pull both covers and clean out the differential, give it a good inspection, and re-fill with quality gear lube. I use RTV, I don't go into the differential enough to pay for the lube lockers and I get a better seal with RTV.

 

[Johnfromphilly]

The word "Major" is a bit of a stretch here but it's a good project to tackle for you. Pull both covers and clean out the differential, give it a good inspection, and re-fill with quality gear lube. I use RTV, I don't go into the differential enough to pay for the lube lockers and I get a better seal with RTV.

Understood on the use of the word major. I guess that is specific to me and relative to everyone's personal experience and comfort level. I have never done anything on a car or truck to this level so it is major to me. I have never even changed the oil myself. Jiffy lube does it for under $40 with a coupon so it never made sense to me. This is my first older vehicle and I am taking this on as a hobby and thought this would be a good jumpoing off point. The pinion leak is a different story, not ready for that.

 

[Cheetokps]

I'm in a similar situation to you, just bought mine a couple of months ago and am also slowly learning how everything works and how to do maintenance. I have the same apparent leak on my rear differential but I am probably going to wait until spring. I've got a bunch of things I want to tackle that I'm waiting until warmer weather for

I also recently was about bumper deep in water, so I probably should replace my fluid anyway

 

[Johnfromphilly]

I'm in a similar situation to you, just bought mine a couple of months ago and am also slowly learning how everything works and how to do maintenance. I have the same apparent leak on my rear differential but I am probably going to wait until spring. I've got a bunch of things I want to tackle that I'm waiting until warmer weather for

I also recently was about bumper deep in water, so I probably should replace my fluid anyway

I am just antsy to get a project going. I have fixed every burned out bulb and messed up wiring issue/ dashboard light. Since I can't drive it I want to work on it. Waiting to find a set of Canyon rims like you have to replace the steel rims currently on mine. Not having much luck finding anything within driving distance that is in good shape for a fair price. Shipping is so expensive on rims it is prohibitive for most private sellers.

 

[Zorba]

I ended up replacing both my diff covers with aftermarket so I could have drain plugs. Some will say that's an excellent idea, others will say "why bother?" and still others will tell you to pull the covers every time to inspect. I used LubeLockers and love them - in fact, one of the LubeLockers was used that came with the used aftermarket diff cover I bought (ARB). It worked just fine!

 

[cliffish]

Understood on the use of the word major. I guess that is specific to me and relative to everyone's personal experience and comfort level. I have never done anything on a car or truck to this level so it is major to me. I have never even changed the oil myself. Jiffy lube does it for under $40 with a coupon so it never made sense to me. This is my first older vehicle and I am taking this on as a hobby and thought this would be a good jumpoing off point. The pinion leak is a different story, not ready for that.

I would pay Jiffy lube $40 to not touch any of my vehicles..lol That is something you should do yourself, if for nothing else, but to get the "feel" of the TJ. Also seeing the oil coming out will tel you a bunch of what is going on in the engine.

 

[Johnfromphilly]

I would pay Jiffy lube $40 to not touch any of my vehicles..lol That is something you should do yourself, if for nothing else, but to get the "feel" of the TJ. Also seeing the oil coming out will tel you a bunch of what is going on in the engine.

Fair enough. Haha. Again, I have no training or history with car repairs, zero. It just wasn't a thing for my family or friends. We did construction not mechanics so this is all new to me.

 

[Johnfromphilly]

Pinion seal leaks are normally fairly slow, I wouldn't expect it to show within a few minutes or even a few hours.

@Jerry Bransford here is a photo from the other side showing the pinion seal. Looks bone dry to me. I cleaned the diff cover and will try to take it out at some point and see what happens.

Thoughts?

 

[Jerry Bransford]

@Jerry Bransford here is a photo from the other side showing the pinion seal. Looks bone dry to me. I cleaned the diff cover and will try to take it out at some point and see what happens.

Thoughts?
View attachment 226828

Looks dry doesn't it! That sure seems to point at the simplest fix, resealing the differential cover on the rear. I think you lucked out!

 

[Johnfromphilly]

Looks dry doesn't it! That sure seems to point at the simplest fix, resealing the differential cover on the rear. I think you lucked out!

And I get to do my first project! It was super tight under there. I am going to have to jack it up and put jack stands in also, first time for that. I have been over the safety on that multiple times but getting under a lifted Jeep is a scary proposition.

I imagine the Jeep should be level when I add new fluid, correct? This is in my garage which has a slight slope for drainage. I plan on jacking it up and using jack stands to give me room for the work then lowering it to level to add the fluid at the end. Is that correct?