Turbo Coupe 8.8" swap into my SVO

[Zap's 85 GT]

Ever since I got my SVO running and driving I've been chasing down noises and vibrations from every part of the car. Things kept getting better and better and I was now down to the final culprit being the rear axle. Some time in the cars past a set of 4.11 gears were swapped in. By the time I got the car the installation of the gear set was evidently flawed because the rear axle had a very pronounced whine starting at 40 mph, and an unnerving rumble during high speed deceleration. Fixing the rear meant new gears, bearings, and installation. I was easily looking at $500. I decided to go another route.



I found a 1987 Thunderbird Turbo coupe in a local junk yard and managed to get the rear axle(minus brakes and axle shafts) for $100. 3.55 gears, traction lock 8.8". I brought it home and installed new axle bearings and seals just to be safe. Bought the proper 8.8" rear brake hose, gear oil, traction lock additive, upper bushings, and I even went so far as to pick up some new brake calipers from NAPA. I had rebuilt the original calipers almost two years ago with a seal kit. I took my time and did everything I could but they didnt seem to last. I could have rebuilt them again but I doubt I'd of had any better luck. A three year warranty and they came with all the new hardware you could ask for. New slider pins and bushings, ant-rattle clips, copper washers, slider pin grease, and even a new bolt for the e-brake arm. $62 ea and the core was $82 ea. The first time I ever had the core cost more than the part.

I needed to remove the Turbo Coupe brake brackets from the axle housing. Did that with grinder and they came off very easily.





After cleaning it up more I then painted the housing with some POR 15 chassis black paint.



The quad shock brackets on the turbo coupe housing are taller than the mustang ones so I marked and made the holes to match. I ran into an issue with the quad shocks but I'll explain that at the end.




After that, swapping everything from the old axle to the 8.8 was straightforward.





Up and into the car.






It all went quite well. Right up to the point where I lowered the car to the ground. When I did that the car was riding high in the rear to the point of there being 3-4" of clearance room the top of the tire to the fender. The suspension would not compress any more. Turned out to be the quad shocks were at their short limit. Meaning the suspension was effectively locked against the quad shocks as they wouldn't compress any more.

I measured the quad shock brackets and transferred over the measurements from my original axle. I don't think I did anything wrong in the way I measured the holes in relation to the difference of the way the brackets are mounted to the axle. I removed the quad shocks for now but am wondering what can be done to make it work. I'll need to play with it at another time.

But that issue aside.... On the road the car drives great. With the proper speedometer gear installed the speedo is accurate to 2mph according to my GPS. There is no more noise coming from the rear end. Hooray! It'll take a little getting used the gearing change. Its not a big difference(4.11 to 3.55) but behind the 2.3 its a bigger deal than if it were behind a 5.0. I'll see how it does in the mileage department too during the next tank of gas. It should start paying for itself. For a total outlay of $150(minus calipers) it was a no brainer swap vs new gears in the 7.5" rear.

[8T6 SVO]

One Heck of a job well done. Last time I swapped a 8.8 for a 7.5, I purchased the 8.8 from FRPP - so I can't help you with the issues regarding the T-bird rear. I'm sure someone here has done it and will chime in. It does look like those quad brackets are slanted back way further on the T-bird rear end compared to the original though.

On the Ford quad shock kit, meant to be installed on 84 and older cars, I think the kit came with brackets for both the rear end and the frame to be installed. Maybe you can find this kit and remove the 87 rear quad bracket completely from the rear end?

[8T6 SVO]

Here's a set of brackets for the frame mount of the quad shocks. Maybe you could install these in an alternate position that would work? Or maybe you could relocate yours if they are not welded to the frame?

http://cgi.ebay.com/ebaymotors/79-04...1%7C240%3A1318

I set of boxed rear control arms will eliminate the need of the quad shocks completely.

[Mad Max]

If memory serve correct. The TC quads mount lower on the chassis with a different bracket than the mustang quads but the frame rail are higher up. The axle mounts are rotated to help with the longer quad mounts which is slightly beter for anti-hop.

Options might be to remove the quads or, move the quad brakets (the frame mounts are easier to move) or the best and most expensive is to put something else on to replace the quads. I think Global West still makes a "mini" bolt on torque arm. Always wanted to try one....

[854vragtop]

Very nice documentation of your work. I have a TC rear end that I've gotten as far as painting. I haven't had the time to complete the installation in my '85 GT convertible, so it's just sitting on jack stands in the garage. My only hold up (besides time and money for new calipers, rotors, etc.) is which flex hose to use to connect my '85 body hardline to the TC axle brake lines. Which hose did you use and did you have to modify or make now axle hard lines?

[martin0660]

Did you tighten all the 4 link bolts with the rear hanging and jack stands under the chassis? (as pics show)

Your bind may not directly be related to the quads as what you describe is how I understood it to be done too (no quads or even brackets on my car). If the bolts where tightened with the suspension in droop, the quads could have been the "last straw" and removingthem allowed it to settle a little. I would still load the rear wheels, loosen, then tighten all the bolts if you did it hanging.

Bob Myers

[Zap's 85 GT]

I used a std 86-93 8.8" rear rake line for a 5.0 car. I modified the rear body mounting point in the past making it dual exhaust friendly. I used the bracket and hard line out of a junkyard car. Two rivits and one flare later was all it needed. When I had the 7.5" rear axle in the car I made a modified brake hose since the dual exhaust 7.5" hose is near impossible to find. I used the original 7.5" bracket off my GT and a new rubber part of the hose from the later 86-93 cars mated together.

I've been turning wrenches for a while and was ahead of the curve when it came time to tighten the control arm bolts. It never even got that far. Even with all the bolts loose, the suspension became locked against the quad shocks as I lowered it to the ground.

[Mad Max]

Have you fixed you quad shock problem yet?

Just a thought but have you tried to to re-angle the mount on the axle? Cut a wedge out of the axle mounts and re-angle them or push them forward. Then reweld them in their new spot.

[Zap's 85 GT]

I have no welder where I'm at. I'll probably just get some better lower control arms and not worry about the quad shocks.