So I want to have a spare diff built for my 03 cobra. I know the obvious differences like the 28 spline open diff. I plan on putting a 31 spline tru-loc and 3.73s in it anyways along with new bearings. Are the mounting points and diff cover mounting the same on the Mark 8 different?
03 Cobra diff vs Lincoln MKVII diff
- Thread starter Othic
- Start date
Anyone have info?
do you mean mark viii?
you could search. the info is avail ;-)
here is what i found:
28 spline
its similar to 99, so you will have to change out flange
there is more webbing on the cobra unit
make sure its a 8.8 & not something out of a cougar/tbird (which i think is 7.5)
also make sure its aluminum not cast
you could search. the info is avail ;-)
here is what i found:
28 spline
its similar to 99, so you will have to change out flange
there is more webbing on the cobra unit
make sure its a 8.8 & not something out of a cougar/tbird (which i think is 7.5)
also make sure its aluminum not cast
Ive owned my cobra for 3 years now and in that time have broken 2 rear ends. The first was on the street after a 3300rpm (slipping) launch, the rear had a low hum that was amplified by the FTBR kit. I drove the car like this for 2000 miles (its my DD) dropped the rear, turns out I spun the carrier bearing opposite the ring gear. So it was rebuilt with frpp and a LPW cover, 2 months later I end up at the track on NT555 at 21psi (which was prepped badly that night) prob 65 deg out 2nd run I launch from 3200-3300rpm (slipping it) and broke a HS 15ft down the track. Get that fixed and the rears making noise again. Back down again, Bearings and races were good but I had 0.008 runout on the carrier. Turns out I tweaked the alum housing itself. I tried to order a new one from ford but they were backordered 2 months out. I did a lot of reading and the factory five guys and the miata club praise the alum ford 8.8 Irs for there cars granted they usually dont put down the power of the typical 03-04 cobra. I found out that the alum mark rears and cast iron tbird/cougar rears will fit (certain years) you just have to replace the differential/gears. I opted for the cast iron unit (much stronger) out of a 97 t bird, I replaced all internals with new parts and 3:73s. Only downside to this is it ads something like 27lbs. possibly heat(if you auto x) Ive had the car this way for 4000 miles now and many hard launches and havent had one problem. IMO the aluminum 8.8 carrier bearing caps are to weak and will flex under hard launches. I debated going solid for a while but I hate the fact of losing the handling and comfort aspects of the IRS. With this set up I think Ive found a happy medium for the car. Heres a few pics and if you have any questions feel free to shoot me a pm.
Case from the Lincoln will work fine, as will the cast iron Supercoupe ones like the guy above used. I would recommend using the LPW cover though, as it is stronger, has a built in drain plug, as well studs to support the bearing caps. As long as you get the 8.8 version, and not the 7.5" you will be good to go. The 31 spline carrier from your Cobra, or aftermarket equivalent will drop right in. Be sure that the shop you have do it uses a case spreader for the aluminum version, or they will never get the bearing pre-load set correctly.
Ford was sold out of Cobra rear housings so I went with a '97 Mark VIII aluminum with MW bearing caps, ratech solid spacer, Detroit truetrack etc. I picked up the entire Mark rear end for.......$100!!! My builder tested it out for cracks, stresses etc. before doing the build. To tell you the truth I'd rather buy a Mark housing which only had to stand up to a auto trans. and 285 crank hp than a ragged out Cobra unit, no matter what the year.
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