Used Diff Gear and LSD Installation

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Used Diff Gear and LSD Installation

July 14, 2020, 10:59:22 AM

I recently came across a pretty good deal for a used set of 3.73 gears and LSD for a Ford 7.5, and I've been wanting a set for awhile now, but haven't been sure if it would be cheaper to buy a used set to rebuild or buy a new set. If I could find a brand new Ford Racing set of 7.5 gears, that'd be fantastic, but they're super rare. So right now, I'd like to see what would be the best option price-wise. Also, what would be necessary to rebuild and install the gears and LSD? I could get a Ford Racing 7.5 Ring Gear and Pinion Install Kit, would that be enough to rebuild the set or would I need something else to rebuild the LSD?

Re: Used Diff Gear and LSD Installation

Reply #1 – July 14, 2020, 04:38:48 PM

Is the 7.5 LSD a Ford clutch and plate type, or is it the Torsen version?

Re: Used Diff Gear and LSD Installation

Reply #2 – July 14, 2020, 05:46:45 PM

It's a factory Ford 7.5 LSD to my knowledge.

Re: Used Diff Gear and LSD Installation

Reply #3 – July 15, 2020, 09:58:15 AM

Well, I know the '84 7.5 I had in my car for a long time was a Torsen unit and not the clutch-disk type. I don't know how long the Torsens carried on in the 7.5's. Any pics of the LSD?

I wouldn't see a problem with a rebuild, etc, as long as you're comfortable performing such a task and reinstalling gears.

I don't know if there is a difference in the internals of the Ford type LSDs between the 7.5 and 8.8 (Just rebuilt the 8.8 LSD in my TBird).

Re: Used Diff Gear and LSD Installation

Reply #4 – July 15, 2020, 10:44:25 AM

Those are the pics I could get of the gears and LSD. I'm not too familiar with differentials on how they go together, so I assumed it was a clutch style, maybe not. I figured if it was a clutch style I could rebuild it myself depending on the difficulty of it, I looked it up and it didn't seem TOO bad. I'm gonna have somone else install the gears and LSD in my car though, that's too much work for me.

Re: Used Diff Gear and LSD Installation

Reply #5 – July 15, 2020, 11:54:48 AM

Yeah, that's a clutch type.
What were the parts out of? I see a toothed gear there, probably for a speedo pick-up.

Re: Used Diff Gear and LSD Installation

Reply #6 – July 15, 2020, 12:52:59 PM

Honestly I don't know, I could ask the guy. I'm assuming out of a Ranger pickup because that's what I see most of these gears and LSD's coming out of.

Re: Used Diff Gear and LSD Installation

Reply #7 – July 22, 2020, 08:37:05 AM

Does anyone else have any input on used gears and LSDs?

Re: Used Diff Gear and LSD Installation

Reply #8 – July 22, 2020, 03:27:21 PM

Why not just keep a lookout for a complete 8.8 assembly with the gears you want already installed? With some patience, there are 87-8 TC rear ends for sale that already have either 3.55s or 3.73 gears in it with the lsd. If you dont want to use the 4 lug disc brakes, just swap your axles and drums on instead.

I've found Fox mustangs being parted out with built rear ends that had upgraded gears, diff, and axles for very good savings over doing it again with your own parts.

Dont know what you are paying for the 7.5 parts, but gear installs run between $250-350 labor plus fluid, shims, and maybe new carrier, pinion, and axle bearings if yours look worn. Just sayin, might want to run the numbers.

Re: Used Diff Gear and LSD Installation

Reply #9 – July 25, 2020, 09:29:08 PM

Hmm I guess I didn't think about the TC swap. I was just worried about biting off more than I could chew with a rear swap, especially if I had to change around axles, brake lines, etc. That's what frightened me away from a Mustang 8.8 swap.

Re: Used Diff Gear and LSD Installation

Reply #10 – July 26, 2020, 02:46:08 PM

Before you try and do an 8.8 swap and just swap over your brakes/axles, you'll want to measure the housing width on your '86 7.5.

At some point in '86, the 7.5's got a wider housing in the TBirds/Cougars.

If it measures roughly 55.5" from to , you have the wider housing.

The "Fox" Mustang, 87-88TC, 93 Cobra, 94-98 Mustang 8.8 housings are all just over 54" to . (As are the 83-85 TBird Cougar 7.5)

Your axles and brakes won't work in those housings.

Re: Used Diff Gear and LSD Installation

Reply #11 – July 26, 2020, 06:38:57 PM

Sweet, thanks for that tip. I guess I'll do a little more research on an 8.8 and TC swap and see if it's something I'd be willing to take on, I did do some research on it maybe a year ago and at that time thought it was a little much, but maybe I'll look again and see what happens.