7.5" Limited Slip Question and Che Lower Control arm review

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7.5" Limited Slip Question and Che Lower Control arm review

May 21, 2017, 07:32:56 PM

Hey All,

I just got done installing CHE performance tubular control arms in my 88' Cougar and couldn't be happier. Absolutely worth the money. Along with throwing on a TC rear sway bar, these arms really tightened up the ride. Now the car inspired confidence while taking fast turns.

My question is regarding doing a rear axle gear swap. I bought a 7.5" trak-loc axle with 3.45 gears out of an 86' TC. My cougar currently has the 3.08 open diff. The TC axle is cosmetically in rough shape and would need new seals and brake job before being installed, whereas my Cougar's open diff is in great shape. This leads me to wonder if it would be better/easier/cheaper to swap the gears and axle shafts from the TC into my Cougar's rear instead of refurbing the TC rear and going through the trouble of installing it.

Thoughts?

7.5" Limited Slip Question and Che Lower Control arm review

Reply #1 – May 22, 2017, 07:24:08 AM

Keep your housing and axles, they're wider than the 86 TC one. Wider axle means wider rear track, and since you seem to be concerned about handling, wider is better. If you're thinking of swapping the gears, I would caution you that unless you have tools for measuring and setting pinion depth and backspacing, You'll likely want to see a pro who specializes in driveline work. If you're looking for something you can do easily yourself, get new clutches for the LSD and keep your 3.08; just bolt the ring gear to the LSD and throw it back in, the backspacing should be more or less right.

7.5" Limited Slip Question and Che Lower Control arm review

Reply #2 – May 22, 2017, 08:02:54 AM

The 88 Cougar 7.5 and the 86 TC 7.5 housings and axles are the same...

7.5" Limited Slip Question and Che Lower Control arm review

Reply #3 – May 22, 2017, 01:24:59 PM

Repainting the TC rear end will easier in the long run than swapping parts around. The only thing is if the clutches for a 7.5 limited slip are hard to find and expensive when you do. For example:

https://www.ringpinion.com/b2c/ProductDetails.aspx?ProdID=1039

This is why most folks avoid them any more and go with the 8.8 rear.

7.5" Limited Slip Question and Che Lower Control arm review

Reply #4 – May 23, 2017, 12:38:43 PM

If you're going to swap gears into your current housing might as well go 3.73s and skip the 3.45s. I ran 3.73s with the stock 5.0 SO and it was happy with them.

7.5" Limited Slip Question and Che Lower Control arm review

Reply #5 – May 24, 2017, 08:55:48 AM

I would prefer to go with a 3.73 for sure but I'm not trying to spend any more money right now :flame:
Is the process of setting the backlash for the gears a real pain in the ass? Would it be worth having a shop do it if I go this route? If so does anyone know how much that costs?

7.5" Limited Slip Question and Che Lower Control arm review

Reply #6 – May 24, 2017, 02:09:45 PM

It cost me ~ $350 to have gears done a couple years ago.

7.5" Limited Slip Question and Che Lower Control arm review

Reply #7 – May 24, 2017, 08:23:13 PM

I'm thinking I'll stick with the original plan and swap the whole axle. Time to order some new wheel bearings, seals, and upper control arm bushings!

7.5" Limited Slip Question and Che Lower Control arm review

Reply #8 – May 27, 2017, 09:22:30 AM

Before you go to all that trouble inspect everything. It may for the most part just need axle seals and a good cleaning inside the carrier which you can do with a couple of cans of brake cleaner. I am not a fan of carb cleaner on the posi clutches but that is just me. You can Google and YouTube how to inspect the clutches on the posi and I would strongly suggest you do this to make sure that they are not burned up (I highly suspect they are). If all you are out is some seals and a set of clutches then its a relatively cheap way to get some performance and no one like the one wheel peel.

If you are feeling super industrious then remove all the braking components (sans the caliper brackets which require axle removal) and BEFORE you tear into the third member, hit it with some oven cleaner use a variety of wire brushes (large and small for the tight spots) and that will get most if not all the dirt and grease off the rear end so you can paint it. This is also nice so that when you are working on it you won't get any in the third member when you take it apart. After you put it back together and before you put the brakes back on hit the whole rear end with some brake cleaner to remove any grease and oil and let it evaporate off. I would then shoot it with some rattle can primer for rusty surfaces and follow that up with a couple of coats of an enamel in a low gloss black.

This is all just me and I usually take my time doing stuff like this as its under the car and I want it to stay there for a long time.

7.5" Limited Slip Question and Che Lower Control arm review

Reply #9 – May 27, 2017, 11:40:27 AM

As a FYI if you need new axle shafts the Moser shafts for a 1993 Mustang Cobra are the correct length: https://lmr.com/item/MOS-93CB-28/1993-Mustang-Cobra-Moser-28-Spline-4-Lug-Rear-Axles

They fit 85.5-88 Thunderbird/Cougar 7.5" drum brake rears, 87-88 Thunderbird Turbo Coupe 8.8" disc brake rears, and 88 Cougar XR7 8.8 disc brake rears.

I've got the 31 spline versions in the 88 Cougar XR7 8.8 under my Thunderbird.