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Need some advice rear differential (dana 35)

D

dutchjeep

NAXJA Forum User
Location
Half Moon Bay, CA
I need some dana 35 advice. Sorry of these questions are off the chart, I have no experience with this. Appreciate any input.

My rear diff (dana 35, with abs) is making a whining noise when under load (whine gone when I release throttle etc.) which is not terrible around town but drives me nuts on longer trips (it's worse between 55 and 75mph). I've chatted with a mechanic and had him testdrive it and he suggested it is the diff backlash being off slightly. Makes some sense to me.

Now, what to do? I've never worked on diffs before, I do have the FSM, and don't mind buying some new tools. Is this backlash adjusment (or does this require a complete overhaul?) something I could undertake on my own?

Or, should I forget about it and have it done. If so, how much would that cost approximately? I have one rough quote for $1100, reasonable?

Other option would be to buy another axle from a junk yard. Is that something I can install myself or do I run into the same problem when I need to adjust that other axle onto my XJ?

Again, sorry if I'm out to lunch on this, but really appreciate any input!

Thanks.
 
since you have ABS, yo ucould always find another D35 at the junkyard. Iwould definatly not sink $1100 in your current axle. D oyo uhave stock gears?
 
Don't spend $1100 bux to have your D35 fixed. That is insane. If you cannot get it fixed for less than $300, go to a junkyard and buy a new axle.
 
A little information would be helpful first. Do you offroad your jeep at all? Or is it a purely street rig?

If you want to keep your ABS then you will need to get another dana 35 from a junkyard. Otherwise you can grab anything you want from under a XJ.

If you offroad at all ditch the ABS and the 35 and grab an 8.25. The only thing you need to worry about is grabbing an axle with the same gear ratio as you currently have. Pull the cover on your old rear axle or read the tag on the axle and match it at the junkyard.

-Alex
 
Thanks guys! Sorry for lack of info. This XJ is for street use only. I don't care much about the ABS though. If better to replace by something else then I'll do that. If Dana 35 is available I'll just use go for that. Doesn't have to be super strong, just needs to be quiet.

The gearing is stock (at least presuming the previous owner didn't change that; but the whole truck was stock (except for the flowmaster) so I don't
reckon he did).

I wasn't planning on spending $1100 on the rear axle. Insane is the right word! If that was my only option I'd buy some good ear plugs:).

So by the sound of it, the simplest way to do this is just get another axle? How much of a job is it to pull my axle and put another one on?

Just trying to set the backlash in my present diff is not really an option then I take it?
 
dutchjeep said:
Thanks guys! Sorry for lack of info. This XJ is for street use only. I don't care much about the ABS though. If better to replace by something else then I'll do that. If Dana 35 is available I'll just use go for that. Doesn't have to be super strong, just needs to be quiet.

The gearing is stock (at least presuming the previous owner didn't change that; but the whole truck was stock (except for the flowmaster) so I don't
reckon he did).

I wasn't planning on spending $1100 on the rear axle. Insane is the right word! If that was my only option I'd buy some good ear plugs:).

So by the sound of it, the simplest way to do this is just get another axle? How much of a job is it to pull my axle and put another one on?

Just trying to set the backlash in my present diff is not really an option then I take it?
Click to expand...


is your Jeep a 5 speed or auto. If you dont already know, auto usually has a 3:55, sometimes a 3:73 and a 5 speed almost always has 3:07. Good stuff to know when you look for a repalcement. Who knows you might be lucky enough to find an axle with a stock posi unit. As far as repaling it yourself, it depends on you mechanical skills. With a direct replacement, its not too bad. The wors part is centering the axle under your rig again, so it doesn't track sideways. If you do decide to go with an 8.25, the u-bolts are different and being that your rig is stock, you run into the whole driveshaft length problem too. Good luck fixing your Jeep. :sunshine:
 
jk333 said:
is your Jeep a 5 speed or auto. If you dont already know, auto usually has a 3:55, sometimes a 3:73 and a 5 speed almost always has 3:07. Good stuff to know when you look for a repalcement. Who knows you might be lucky enough to find an axle with a stock posi unit. As far as repaling it yourself, it depends on you mechanical skills. With a direct replacement, its not too bad. The wors part is centering the axle under your rig again, so it doesn't track sideways. If you do decide to go with an 8.25, the u-bolts are different and being that your rig is stock, you run into the whole driveshaft length problem too. Good luck fixing your Jeep. :sunshine:
Click to expand...
It's an auto. Is there anyway to find out whether I have a 3:55 or 3:73 gear ratio? This one has a towing package so according to the wikipedia page it should have a 3:73 gearing. Always true or not? Is it stamped somewhere?
 
Just took the diff covers off to do an oil change (was due anyway), cleaned all the bolts but didn't find a tag of any sort. Well, the gearing is really not that much of an issue right now (no complaints).

I just want to get rid of the whine. Is there any good write-ups (like 'idiots guide to..') about backlash adjustments? Or is this something that's really out of my league? I have the FSM but I think I'll need a little more help than given there.

Also, put up some pictures of diff inside. Any obvious wear visible to the trained eye?

In short, I'm really pretty clueless about diffs, but very much willing to learn, and just want to find a way to get rid of the whine that I believe is a backlash adjusting problem (so I was told by a dealer mechanic). Any advice (or redirections) on better diagnosing the problem or how to solve this would be great!

Is really just replacing the whole axle the best thing? It seems such overkill.

Thanks!

Tim
overview.jpg



zoom1
zoom2
 
dutchjeep said:
Thanks guys! Sorry for lack of info. This XJ is for street use only. I don't care much about the ABS though. If better to replace by something else then I'll do that. If Dana 35 is available I'll just use go for that. Doesn't have to be super strong, just needs to be quiet.

The gearing is stock (at least presuming the previous owner didn't change that; but the whole truck was stock (except for the flowmaster) so I don't
reckon he did).

I wasn't planning on spending $1100 on the rear axle. Insane is the right word! If that was my only option I'd buy some good ear plugs:).

So by the sound of it, the simplest way to do this is just get another axle? How much of a job is it to pull my axle and put another one on?

Just trying to set the backlash in my present diff is not really an option then I take it?
Click to expand...

First off, checking gear pattern and backlash is simple. It only takes a few minutes after you have the cover off.
If you have a FSM and access to NAXJA you have all the info to do this.
If you dont mind owning tools, I would purchase a tube or bottle of gear paint and a dial indicator and check the pattern and backlash. Thats a simple operation and it will either prove or disprove excessive backlash and it will insure that your gear pattern is where it should be. With those things eliminated and after a good visual examination of everything, you can pretty much narrow any differential noise down to bearings.
Once you have narrowed it to bearing noise, then its time to start thinking about an axle swap. When you start replacing the pinion bearings, you're looking at resetting the pinion depth and pinion preload, it gets alot more complicated. Its nothing a mechanically inclined person with the right tools and the above mentioned resources cant handle though.
AND, dont pay anyone $1100 to do anything. Thats insane. Checking pattern and backlash shouldnt cost any more than $80 at a shop.
If you have to actually reset your backlash then I would start looking for another axle because something bad has happened to that axle for the backlash to suddenly go out. You would probably end up resetting the pinion and everything to be sure its good to go.

BTW did the noise start suddenly or gradually over time?
Change the oil and see if the noise goes away before you do anything. Check and rotate your tires, sometimes they can whine if they have odd wear or are low on air.
 
Last edited:
Ray H said:
First off, checking gear pattern and backlash is simple. It only takes a few minutes after you have the cover off.
If you have a FSM and access to NAXJA you have all the info to do this.
If you dont mind owning tools, I would purchase a tube or bottle of gear paint and a dial indicator and check the pattern and backlash. Thats a simple operation and it will either prove or disprove excessive backlash and it will insure that your gear pattern is where it should be. With those things eliminated and after a good visual examination of everything, you can pretty much narrow any differential noise down to bearings.
Once you have narrowed it to bearing noise, then its time to start thinking about an axle swap. When you start replacing the pinion bearings, you're looking at resetting the pinion depth and pinion preload, it gets alot more complicated. Its nothing a mechanically inclined person with the right tools and the above mentioned resources cant handle though.
AND, dont pay anyone $1100 to do anything. Thats insane. Checking pattern and backlash shouldnt cost any more than $80 at a shop.
If you have to actually reset your backlash then I would start looking for another axle because something bad has happened to that axle for the backlash to suddenly go out. You would probably end up resetting the pinion and everything to be sure its good to go.

BTW did the noise start suddenly or gradually over time?
Change the oil and see if the noise goes away before you do anything. Check and rotate your tires, sometimes they can whine if they have odd wear or are low on air.
Click to expand...
Thanks for the input!

Noise increased gradually over time. It's still not terrible but on longer (highway) drives it can drive you (me) nuts. I just put some new oil on it (75w140 synthetic gear oil) so we'll see what it does. On short test drive not much difference. Will check this week on longer drive.

I don't mind owning tools. But what exactly do I do with the gear paint (assume: put on and rotate axle to see what the wear is like?)? In other words, what to look for? If this is explained elsewhere just redirect me. And for the dial, what/where exactly do I measure?

Thanks again!
 
Is it worse in reverse than it is forward? In my experience it's often worn bearings. When the wheel bearings are seriously loose, the seal starts to seep. If you take the drum off you can look for seepage, then try and wiggle the axle up and down. This is the play in your bearings, I can tell by feel if they are OK or not. There will be some slight movement, like a few thousandths to around .010" (this is excessive). The first indicator is a leaky seal, but the seal can be bad and the bearings still be good (on occasion, sand or mud eats up the seals). If the bearings are worn, the seal will most always leak, if not now, soon. Pinion bearings, same with the seal, try moving the pinion up and down left and right, not rotation, but perpendicular and horizontal, try moving it in and out. I usually try to feel the movement with my palm and kind of slap it. Spider gears sometimes look burnt, the edges of the teeth are rounded. When the thrust washers get worn, the gears get kind of sloppy in there.
And if yours is noisier in reverse than driving forward, the carrier bearings are likely worn. You can test this with the cover off and by using a pry bar or piece of wood to pry the carrier up. Any upward movement at all and it's time for bearings. I'd put my new carrier bearings in, check the contact patch and drive it. I've yet to have any serious issues.
Bearings aren't really that expensive. I actually have a set (carrier and pinion) with the centers sanded out (they slide on and off), that I use for setup.
I'd throw a hundred dollars worth of bearings at it, chances are it will be 90% quieter if not perfect and last for another 50,000 miles.
In my experience any time after 130,000 miles or so it's usually time for some new bearings and often the carrier bearings are the first to go and possibly a set of spider gears and thrust washers a close second, then the pinion bearings or wheel bearings. There can be early failure on any bearing, but I rarely change any on a hunch. I've had wheel and pinion bearings last well over 200,000 miles.
With the carrier out you can rotate the pinion and often feel if the bearings are damaged, you can feel a little hitch and rumble, if they are bad or going bad.
Setting backlash on a used set of gears, seems kind of counterproductive to me, gears wear in, in a certain way. I always try to get used gears back as close to the original position as possible.
If you replace the whole rear end, try to get something with low mileage, which may be hard to find or it may not be much better than what you have. I replaced one burnt (black and blue with pits) set of spider gears at 60,000 miles.

Gear paint, toothpaste, white grease, copper paste, I've used them all checking my contact patch. There are pictorials on how the pinion and ring gear should mesh, you check the point of contact (patch) with something that leaves a color (stain) after you've cleaned all the oil off. The pictures show you how a good patch should look and how it should be positioned on the ring gear teeth. IMO it's less critical that it be correct on a used gear set, than it is to get the contact patch back to where it was. You can see the wear pattern in a used set of gears, rarely do they look like the pictorial ideal.
 
Last edited:
dutchjeep said:
I don't mind owning tools. But what exactly do I do with the gear paint (assume: put on and rotate axle to see what the wear is like?)? In other words, what to look for? If this is explained elsewhere just redirect me. And for the dial, what/where exactly do I measure?

Thanks again!
Click to expand...

Your FSM has several pages dedicated to checking and setting gears.
Like 8mud said, the paint is to check your pattern.
The dial indicator with a magnetic base is to check your backlash. I dont recall what the spec is for used gears, again, should be in the FSM.
 
8Mud said:
Is it worse in reverse than it is forward? In my experience it's often worn bearings. When the wheel bearings are seriously loose, the seal starts to seep. If you take the drum off you can look for seepage, then try and wiggle the axle up and down. This is the play in your bearings, I can tell by feel if they are OK or not. There will be some slight movement, like a few thousandths to around .010" (this is excessive). The first indicator is a leaky seal, but the seal can be bad and the bearings still be good (on occasion, sand or mud eats up the seals). If the bearings are worn, the seal will most always leak, if not now, soon. Pinion bearings, same with the seal, try moving the pinion up and down left and right, not rotation, but perpendicular and horizontal, try moving it in and out. I usually try to feel the movement with my palm and kind of slap it. Spider gears sometimes look burnt, the edges of the teeth are rounded. When the thrust washers get worn, the gears get kind of sloppy in there.
And if yours is noisier in reverse than driving forward, the carrier bearings are likely worn. You can test this with the cover off and by using a pry bar or piece of wood to pry the carrier up. Any upward movement at all and it's time for bearings. I'd put my new carrier bearings in, check the contact patch and drive it. I've yet to have any serious issues.
Bearings aren't really that expensive. I actually have a set (carrier and pinion) with the centers sanded out (they slide on and off), that I use for setup.
I'd throw a hundred dollars worth of bearings at it, chances are it will be 90% quieter if not perfect and last for another 50,000 miles.
In my experience any time after 130,000 miles or so it's usually time for some new bearings and often the carrier bearings are the first to go and possibly a set of spider gears and thrust washers a close second, then the pinion bearings or wheel bearings. There can be early failure on any bearing, but I rarely change any on a hunch. I've had wheel and pinion bearings last well over 200,000 miles.
With the carrier out you can rotate the pinion and often feel if the bearings are damaged, you can feel a little hitch and rumble, if they are bad or going bad.
Setting backlash on a used set of gears, seems kind of counterproductive to me, gears wear in, in a certain way. I always try to get used gears back as close to the original position as possible.
If you replace the whole rear end, try to get something with low mileage, which may be hard to find or it may not be much better than what you have. I replaced one burnt (black and blue with pits) set of spider gears at 60,000 miles.

Gear paint, toothpaste, white grease, copper paste, I've used them all checking my contact patch. There are pictorials on how the pinion and ring gear should mesh, you check the point of contact (patch) with something that leaves a color (stain) after you've cleaned all the oil off. The pictures show you how a good patch should look and how it should be positioned on the ring gear teeth. IMO it's less critical that it be correct on a used gear set, than it is to get the contact patch back to where it was. You can see the wear pattern in a used set of gears, rarely do they look like the pictorial ideal.
Click to expand...

Haven't noticed any noise in reverse. Also the whine is only there when under load. When let go of throttle it's gone. That's why I originally didn't think it was bearings (correct?).

Anyway, what I think I'll do is drive it for a week (200 miles or so) with the new oil on the diff, see how it does (don't expect much of that). Then I'll check the bearing play and seal leaks as you recommended. I'll get some gear paint and a dial to do some measuring to at least narrow down the problem (bearings, backlash, gears). Can I get a dial like that just at Napa or better to shop elsewhere?

Man, I wish I had a bucket of time somewhere:).

Thanks again guys! Really appreciate the help!
 
Tommy4949 said:
So, dutchjeep, how did this turn out? I have the exact same problem with my D35.
Click to expand...
It turned out so, so. I changed the oil with a heavier weight, and it improved matters slightly. After that I basically ran out of time and monitary resources. So over the last weeks I've been trying real hard to convince myself that the noise is really much better now. It is not. My solution is to take the old Taurus for the long highway cruises (better mpg's also:)). On shorter distances the diff noise is in the background and the XJ is great; it's only on scales of hours that it gets really annoying.

So I have basically not made any real progress. Sorry. Need time!

Good luck!
 
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