Diff swap or rebuild?

[SamC777]

94 Ranger, 3.0, 4WD. Dana 35. 3.73 7.5" ~330k miles

Earlier this month, my truck started making a rhythmic "thud" sound. Lifted the rear end up and drove it and sure enough, it was coming from my diff. I'm told this could be the pinion bearing, which makes sense to me because there were a lot of metal shavings on the ABS sensor when I replaced it the month before.

The fluid is 3 years old, and it's had about 25k miles since then. The ring gear has been missing a tooth since before I bought this truck 5 years ago, but I haven't had any noticeable issues while driving it. However, my thinking is that if I'm going to pull the ring and pinion out to replace the bearing, I may as well replace those too while I'm in there. That said, I've never serviced my diff beyond a fluid change. I'm certain I can figure it out, but I won't know for sure what else is damaged and what's not. The whole differential might need to be replaced for all I know.

On the other hand, I could just go to the Land of Misfit Parts and pull a rear end. I'm uneducated in this area as well, as once again, I don't know how to tell a good one from the bad even if I pull the cover off. But this may be the simpler (and possibly cheaper) route. Additionally, I've been told that the 8.8" gear is more reliable than the 7.5". Is this true?

Which option do you folks recommend?
Do you have any advice on what to look out for?

Thanks

 

[Northidahotrailblazer]

When I tried to sell my 7.5 no one wanted it. I’m sure you could get one from a junk yard for cheap. Under or around $100 bucks. A gear setup kit will cost you around $100 bucks also. Which is the better way to go rather than just buying bearings.

you can’t just replace the bearings, and not check gear patterns. new bearings will make tolerances change, and to do it right you will have to pretty much reset up the gears. Which shouldn’t be to far off. Since you’re not regearing. You don’t know what’s wrong until you pull the cover. You could have more damage than a bearing and at that point it’s way cheaper to just get a junk yard axle.

 

[Eddo Rogue]

I would rebuild it. Whatever you pull is not gonna have fresh internals. Probably will need seals and stuff anyways.

I done a few ring and pinion jobs. Honestly its not rocket science. Pretty much a magnetic dial indicator is the only unique special tool required.

I thought reading the gear mesh pattern was some kind of dark voodoo art, but it quite obvious to tell. Most rebuild kits come with the pattern marking paint stuff.

Do yourself a favor and get the complete kit, not just the ring and pinion...the kit has all the seals, gaskets, bearings, shims, crush sleeve etc...

Oh and trick of the trade is give the crush sleeve a few whacks with a brass hammer before torquing down to ensure it crushes down nice

The only real quessing game is getting the shimming right, but I have never had to re shim and measure again more than twice...maybe lucky.

 

[CamTheHedgehog]

I would rebuild it. Whatever you pull is not gonna have fresh internals. Probably will need seals and stuff anyways.

I done a few ring and pinion jobs. Honestly its not rocket science. Pretty much a magnetic dial indicator is the only unique special tool required.

I thought reading the gear mesh pattern was some kind of dark voodoo art, but it quite obvious to tell. Most rebuild kits come with the pattern marking paint stuff.

Do yourself a favor and get the complete kit, not just the ring and pinion...the kit has all the seals, gaskets, bearings, shims, crush sleeve etc...

Oh and trick of the trade is give the crush sleeve a few whacks with a brass hammer before torquing down to ensure it crushes down nice

The only real quessing game is getting the shimming right, but I have never had to re shim and measure again more than twice...maybe lucky.

Don't they also make intentionally slip fit bearings for setting up the shims, so you aren't pressing bearings on and off constantly?

 

[sgtsandman]

Don't they also make intentionally slip fit bearings for setting up the shims, so you aren't pressing bearings on and off constantly?

The shims fit between the bearings and the housing for the carrier, if I remember things correctly. So once the bearings are pressed on, you shouldn't need to mess with them again while trying to set the back lash and tooth engagement.

For the pinion, on the other hand, that is a different story. I remember a couple people using an identical brand bearing to the one they are going to permanently install for setup. They reamed out the inside of the bearing so that it would fit snug but not need a press to get it on and off the pinion. Once they got the pinion depth right, then they would press on the permenant bearing for final installation.

 

[Roert42]

Don't they also make intentionally slip fit bearings for setting up the shims, so you aren't pressing bearings on and off constantly?

I hogged out the id of the old bearing I was replacing last time I’d did it.



If you have to buy new gears and everything, it would be easier to just get a new axle. If the new axel is going to need seals and such, it’s probably a wash.

 

[19Walt93]

I would tear it apart and see what you've got before deciding or buying any parts. My truck came with a 3.73, Traction Lok, 8.8 rear that had the spring pads moved to the bottom of the axle tubes to lower the truck. I was using a C4 with no overdrive so I was going to swap in some 3.08's. I found the pinion flange and both axles scored where the seals rode so they were junk, the Traction Lok clutches were worn to metal and grinding into the differential housing so it was junk, and the spring pads were welded on at 2 different angles- neither one was right.
I rebuilt my spare Mustang II 8 inch rear and got some spring pads and 5 lug axles from Currie.

 

[scotts90ranger]

I would replace the whole axle, way cheaper, sure it's unknown but setting up gears isn't for everyone...

Finding a '93-09 rear axle with 3.73's shouldn't be all that hard.

 

[scotts90ranger]

Just a note, I'm not saying this because I think you can't or shouldn't, and I for sure understand the want to be able to do everything yourself, I haven't farmed anything out but windshields and tire balancing for many years (conveniently I do have a friend that does transmissions for a living so that helps greatly there...).

Assuming you have a spare vehicle and are not trying to get this done over the weekend with just youtube videos so you can make it to work on Monday, give it a shot but you'll have at least $200 in gears, another $150 in a master rebuild kit or you could just get a used axle for $150 to $300 and throw the axle seals and maybe pinion seal in and call it... swapping axles is simple, it was one of the first modifications I did on my '90 going from 3.08 gears to 3.73...

 

[SenorNoob]

I'd rather go the axle swap route myself. I've done straight gears on a conveyor and it was a nightmare.
Too bad the 4.10 Dana 35 is as rare as quality pictures of bigfoot.