on October 2, 2010, 2:59 pm, vernlee wrote:

Thunderbird IRS Traction-Lok Limited Slip
The independent rear suspension (IRS) found on 1989-1997 Thunderbird's and Lincoln Mark VIII's are different from the well known solid axle's found on Mustangs (FOX or SN95), and other rear wheel drive Fords. I will refer to the MN12 Thunderbirds differential here only. The differentials for the MN12 Thunderbirds come in two sizes 7.5 and 8.8 (diameter of the ring gear). All Thunderbird SC's came with 8.8 differentials and depending on the transmission (automatic or manual) either 2.73, 3.08, or 3.27 ring and pinion gear set. If you decide on replacing or upgrading your Traction-Lok Limited Slip there are some important things to keep in mind. When upgrading the 8.8 Traction-Lok unit you will find a lot of 8.8 units that are made to fit the solid axle cars but, will not fit the IRS cars. The MN12 8.8 and 7.5 differentials use a 28-spline shaft. The difference between the standard solid axle and the IRS differential is a "Step" (grove) in both differential side gears in order to retain the Circlip (C clip) that holds the Halfshafts in place (see diagram). A "Step" is a grove that will allow the Circlip (C-Clip) to slip over the Halfshaft and secure the Halfshaft in the differential. The differential has precise tolerances and should not be disassembled or assembled without the proper tools and experience. When replacing or adding a Traction-Lok Limited Slip to your SC that may or may not have one installed the easiest ways is to get a Traction-Lok Limited Slip unit from Auburn Gear Inc. 219-925-3200. High Performance unit for standard OE replacement part# 542079 or Pro Series unit part# 542080 for better traction and faster engagement. The average street price for the High Performance unit is $340.00 and $410.00 for the Pro Series. Torsen also sells a limited slip differential through Ford Racing part number M-4204-T28 unit is $450.00 through Ford Racing By, Rich Thomson

on October 5, 2010, 9:19 am, Daze wrote:

Thanks for the fantastic info!!!!

I really appreciate you posting all of this. It is a great resource. I would still like to see some picture of all the alignment adjustments. Alos I was doing a little poking around on line and found a web site that you might find interesting.
http://www.primequip.net/products/Project_427/rear_end.htm

on October 5, 2010, 9:41 am, vernlee wrote:

Thank you for this info, I guess I'm at the point of getting my axles shortened, Most people tell me NOT to shorten them, instead have new ones made or the old ones resplined,I'm trying to find the best source for this ??

Vern

on October 5, 2010, 4:55 pm, Ralphy wrote:

Daze, tanks for the link!

Vernlee, boy oh boy you are going in a wise direction. The ford IRS is now the number one choice with the Cobra kit guys. There's lots of info around. A company called RCC Specialties builds a IRS unit with a 9" center chunk. Also in Daze link there is a reference to FFR wich is Factory Five Racing. They have their own forum with lots of members. Also Search Club Cobra. They may be helpfull.

Good Luck

http://www.kitcarmag.com/howto/rcc_specialty_products_ford_9inch_irs_cobra_replica/index.html

http://www.clubcobra.com/forums/index.php

http://parts.factoryfive.com/newcatalog/chassis/irs.htm
http://www.ffcars.com/

on October 5, 2010, 6:48 pm, vernlee wrote:

Well we will see if my choice was wise or not. I spent an hour and a half trying to get the C clips out of the pumkin tonight so I can pull the half shafts, and still didn't get them out.Got mad so I walked away, I'll try again tomorrow,Also I see the difference now between a regular 8.8 and a IRS,as far as the C clips are concerned,I think I can modify the normal 8.8 side gears in my trac lok to work, or I'll see about just switching the two side gears from the open irs unit into the trac lok unit.

on October 6, 2010, 6:55 pm, vernlee wrote:

Got the cir clips out
After another hour today trying to get the cir clips off the half shaft with no luck,I'm standing there studying this thing when I took my screw driver and stuck it between the side gear and case and pryed the other direction and the gear just popped off,leaving the shaft with cir clip in place,Axel pulled right out,So you don't have to remove the pumpkin cover,just pull the half shafts out,simple as that,I'd feel more like the idiot I'am but I'm so happy to get them out I'll put it down as lack of experience and pass it along 

on October 7, 2010, 8:16 pm, irstang wrote:

Thought you might find this helpful:
www.davestriblingrestorations.com

Drill down under products to find IRS installs in vintage Mustangs

on October 8, 2010, 6:37 am, vernlee wrote:

irstang, thanks for the site info,Another site I like is jefflilly.com, click on muscle cars and check out the mustang they call ''frankenstang''

on October 8, 2010, 10:50 pm, irstang wrote:

FrankenStang
Found FrankenStang in the gallery. Really cool! The metalwork is awesome. Is this your car? I really enjoy custom Mustangs. They are like early Fords used to be. Lots of them out there so why not style 'em how you like. My 'vert has the same blended headlight and tail fin bezels. Also, filled the cowl vents and I am running a tube up front like a '57 Ford. Making the headlights removable and adjustable is a fun project.
I thought seriously about the Cobra IRS for my '65. I shied away because I was worried about the upper arms clearing the "frame rails". I was not sure how to go about narrowing the assembly, either.

Are you going to narrow the rear or just flare the fenders?

on October 9, 2010, 6:42 am, vernlee wrote:

Oh how I wish that was my car  I'm in the process of shorting the irs half shafts,I don't care for flared fender wells jmo.I would like to see a picture of your car.I'll fill you in on my progrss on the irs install, but I think it is going to be slow going ( time and money )

Vern