ImplicitWeevil

Hello! So yesterday I was driving into work and the vehicle began making a whirring/whining noise. It bothered me, but I live in Alaska and cars make noises sometimes; especially because I'm rocking studs and the highway was completely clear (I hadn't driven the vehicle in these conditions before). I get to work just fine, but when I go to leave it acts like something is frozen underneath. That is, I let the clutch out and it jerks forward and starts shuttering along. I decided to get it towed before any more damage occurred. When the driver arrived he inspected the driveline while I crept forward in 1st, he said the driveshaft was spinning before the wheels even did anything. When he winched it onto his flatbed I also saw an inconsistent speed with the driveshaft/wheels. It's also worth noting the diff appears wet. What I'm thinking is the diff leaked and it just burned up. Which sucks. I've never dealt with any driveline issues before, so I'm looking for a place to start here. Is there a way to just replace the internals or is that a PITA? Am I just going to have to swap the whole diff? How would I go about that? Do... do I even have to jack it up?? I've done a bit of work on vehicles but it's all been fwd. A head here, wheel bearings there, cv joint, etc. VIN is 1FTEX14G4FKA43624 (1985 f150 4WD Supercab with a 351w 2bbl carb) if that helps. Let me know if you need more info, and thanks for the help!

ImplicitWeevil

Any suggestions or do ya'll need more info?

Edit: I should clarify, I'm just looking for a starting point; something to get me going. On my next days off I'm going to figure out how to open the thing up and look in it. After that I guess I'll have a better idea of what needs to be done. I'm just trying to get an idea of how this is going to go/things I should start preparing for. And how much will a rebuild likely cost. Or should I just get a rear end from a different vehicle? What years are good to put in this truck? Can I cross match from rangers/etc?

Johnboy429bbf

How long have you had the truck? Are you sure this isn't something someone just slapped in to get it going. If it were me I'd just find a whole rear end to replace it with. Check to see if there's still an ID tag on the rear end. Should be 9" rear end. Other wise your looking a fairly labor intensive Job. If you do replace the rear end be sure the buy new u bolts even if you mange to get the old ones off with out cutting them. I destroyed a Dana 60 because I tried to save a few bucks and reused my old u bolts

Also are you sure the gear ratios matched up between front and rear

ImplicitWeevil

I haven't had it long; probably since the beginning of winter. I haven't driven it much, either. I'm thinking it might have sprung a leak (it looks wet, but everything always looks wet lol), but I've heard they make a lot of noise if they're low on oil. I can't be 100% on whether or not they match. I've only driven it once in 4wd, but it seemed to handle well. I didn't notice anything odd. Is it possible to destroy the diff, even using it in rwd, if the ratios don't match? I'm thinking that might just be the route I'll take. Rebuilding seems like a lot of unnecessary work on this vehicle. I'll have to get under there when the sun comes up. Hopefully there's some form of identification left on there. Things get pretty rusted up in AK. Dang! That sucks; did they snap? I'll be sure to heed that advice.

Johnboy429bbf

You can probably vin your truck on here and get your gear ratio. Then buy the replacement even if the tag is gone.

Chris_1

iTrader: (1)

You should have a sticker on your driver's door post with lots of useful info including a differential code which you can use to look up your gear ratio.
Fixing the internals is not a learn as you go job there's a lot of fancy measuring to do (unless it's just the spider gears, you might be able to tackle that).
You'll probably be hunting for a whole different diff with the same gear ratio as what you have now, and just having the whole thing swapped in.
I would think it should be an 8.8" diff given the year of your truck.

ImplicitWeevil

Hey guys, sorry I've been mia. Work and other appointments had me down, haha. Anyway, here's a pic of the driver side sticker - along with various other bits of under-business. I've managed to find some places that might have rear ends for me. I guess I just need to figure out which one I need, and how to transport it XD

Chris93XLT

I would rebuild it or have it rebuilt vs buying a used one that may go out again.

Chris_1

iTrader: (1)

That's a 9" limited slip. rebuilding it is a good option. The good thing about a 9" is that you should be able to put the truck up on jack stands, pull you driveshaft, pull your axle shafts part way out, and drop that whole center section out.
Then you can take it somewhere, get it fixed and throw it back in.
No messing with brakes, brake lines, sway bars links, U'bolts and a whole pile of other things that can go wrong swapping out an old diff.
Lots of times when you add it all up, it's cheaper to get what you've got fixed than buy a whole bunch of parts to fit somebody else's old used diff under your truck.

Chris93XLT

Yep way better to just rebuild it. While you have it pulled apart Id go ahead and pull the shafts and add new bearing and seals thats pretty easy and cheep insurance you wont have to go back in there any time soon.