Can i swap differential gears myself?

BitchinCorolla · Oct 9, 2023

I’ve been told by my friends that DIY install of new rear gears is pretty difficult and I should let a shop do it. I’m just wondering if thats true or if I could do it myself. I don’t have a hydraulic lift but I can jack the car up. Hardest thing I’ve done is midpipe and catback install. I’d also be adjusting the odometer and speedometer to be accurate.

badass98svt · Oct 9, 2023

I'd honestly leave that to a competent shop if you have any doubts. It is a bit involved and you would need to buy a new tool or 2, too

BitchinCorolla · Oct 9, 2023

badass98svt said:
I'd honestly leave that to a competent shop if you have any doubts. It is a bit involved and you would need to buy a new tool or 2, too

Thanks. Any idea what it might cost me?

96blak54 · Oct 9, 2023

If you stick with ford gears the swap is nearly direct, but thats not saying properly setting up isnt necessary. You gonna need dial indicator and some shims to get it right.

ttocs · Oct 9, 2023

I asked around to find out if I had any friends that had done it before that could give me a hand and found one of my good wrenching friends that said "Done a bunch, no big deal!" so I thought I would give it a try myself. I read everything I could find for instructions, watched a few youtube vids and thought that any other questions he would be able to answer. You can imagine my surprise/disappointment when he arrived and said that first we should watch a youtube vid. So we did and then I slowly discovered that there was no way in hell he had ever done this himself. We were not too far into it before I noticed that it wasn't going back together the way the video showed and we should be able to turn it now but we can't. He wanted to keep going but I shut it down and took the rear end to a shop.

lwarrior1016 · Oct 9, 2023

I built my first diff at 20 years old, under the oak tree with a Haynes manual and some will power.

It is difficult to do without a hydraulic press. You’re going to need bearing pullers, race installers, long punches, a dial indicator, a vernier caliper, a low inch pound dial type torque wrench, a HUGE breaker bar, a large socket for the pinion, a rubber hammer, a slide hammer for axle bearings, and a whole lot of want to.

I did mine the hardest way I could the very first time around, and every time I did one after that it was easier. When I did them at the shop, it was about an 8 hour job. And you better hope you get the pinion depth right the first time, if you don’t, you’ll need a new inner pinion bearing and race.

r3dn3ck · Oct 9, 2023

It's going to have some trial and error involved and it's really easy to get some just a little not right and burn out a rear end. With all the special tools involved, I just give it to the local driveline shop and let them do it. Costs a chitload for an IRS cobra but for a stick axle, shouldn't be but a few hours labor.

lwarrior1016 · Oct 9, 2023

r3dn3ck said:
It's going to have some trial and error involved and it's really easy to get some just a little not right and burn out a rear end. With all the special tools involved, I just give it to the local driveline shop and let them do it. Costs a chitload for an IRS cobra but for a stick axle, shouldn't be but a few hours labor.

Which is odd because the cobra diff is easier. You do it all on the bench.

BitchinCorolla · Oct 9, 2023

Thanks for the advice everyone… think I’ll be sticking to the shop lol.

cobrajeff96 · Oct 10, 2023

Just make sure they use solid spacers for the carrier bearings and not those wafer-thin shim packs from Amazon or Summit. A real shop will use solid spacers.

ttocs · Oct 10, 2023

great advice.

cobrajeff96 said:
Just make sure they use solid spacers for the carrier bearings and not those wafer-thin shim packs from Amazon or Summit. A real shop will use solid spacers.

Mustang5L5 · Oct 10, 2023

Gears are about the only thing i've never done on my car. I'm tempted to try it however as I like to think my skills have improved to the point where I am able to...

However part of me just wants to pull the axle out and drop it off at a shop and let them handle it.

maillemaker · Oct 10, 2023

ttocs said:
I asked around to find out if I had any friends that had done it before that could give me a hand and found one of my good wrenching friends that said "Done a bunch, no big deal!" so I thought I would give it a try myself. I read everything I could find for instructions, watched a few youtube vids and thought that any other questions he would be able to answer. You can imagine my surprise/disappointment when he arrived and said that first we should watch a youtube vid. So we did and then I slowly discovered that there was no way in hell he had ever done this himself. We were not too far into it before I noticed that it wasn't going back together the way the video showed and we should be able to turn it now but we can't. He wanted to keep going but I shut it down and took the rear end to a shop.

LOL! Talk about getting your bluff called!

Mustang5L5 · Oct 10, 2023

The ericthecarguy videos on the diff rebuild and gear install are pretty good. Those are the ones I watched a few times.

My '00 needs the limited slip rebuilt. I feel that is in my wheelhouse. On my Fox i want to swap gears from 3.73's to 3.31's and don't want to pay a shop to do it since it's such a small change in gearing.

Wood's 5.0 · Oct 10, 2023

Let a competent and reputable shop do it.

BitchinCorolla · Nov 16, 2023

Alright so I’m a procrastinator and am only just now getting the gears installed. Got a trustworthy shop willing to do it for ~400 not including speedo correction. I was originally planning on replacing my speedometer gear but according to LMR they don’t make gears with enough teeth, so I’d have to replace the drive gear in the transmission. Not sure if I can do that… so I am wondering if there are higher toothed speedo gears out there or perhaps an alternative?

Mustang5L5 · Nov 16, 2023

23 tooth is as high as it goes. Any higher and the teeth just become too thin and run the risk of stripping

Ford technically only made up to a 21-tooth gear. The 23-tooth was Chrysler part# J3167393 and it's what you would order back in the day. (now discontinued) The usual sources however now repop that gear.

Other option is aftermarket speed cal boxes or a tune perhaps?

b1pig · Nov 16, 2023

I've always compared it to an engine rebuild. If you have true experience in rebuilding engines (plural), then regearing an axle would not be beyond your skill set. A couple of additional special tools.

The best investment i ever made for axles was a pinion bearing removal tool. Will also work on the carrier bearings.... at least for Jeeps. LOL that's where most of my experience lies. Once you get close on the setup, you can tighten up your tolerances pretty quick.

r3dn3ck · Nov 16, 2023

Can that not be dealt with in the tune? It's a 98 right? I haven't done a custom tune in 20 years but I recall that rear gear could be dealt with in the tune.

BitchinCorolla · Nov 16, 2023

r3dn3ck said:
Can that not be dealt with in the tune? It's a 98 right? I haven't done a custom tune in 20 years but I recall that rear gear could be dealt with in the tune.

That’s on 99 and up where a tune will correct it. On the 98 and below it’s mechanical gears.