Tbird IRS

[ultraranger]

I have a 1989/'90 Thunderbird SC IRS rear assembly sitting in my shop. It doesn't have aluminum lower control arms but it does have a 3.27:1 ratio with a Traction-Lok differential.

....T-Bird IRS just after I had gotten home with it and before it was pressure washed. It looks a lot better now than it did in this photo.

http://i1093.photobucket.com/albums/i42 ... 0fd2f0.jpg

[elgemcdlf]

Maybe the SC version did not have the aluminum lower control arms. Mine is a '95 out of a 4.6 Thunderbird. It came with aluminum lower control arms, open diff, 8.8, 3.08 final drive & cast differential housing. I took a Trac-Loc unit from a Mustang & put 3.55 gears with it & into the cast housing. I had the spyder gears machined for the retainer clip. Not a big deal just a small groove put in them. Future plans call for the aluminum housing from a Lincoln. I almost had one a couple years ago but it disappeared from the salvage yard (the entire rear suspension) before I could get it out.

[ultraranger]

I'm not sure if at some point Ford began putting aluminum lower arms on the Thunderbird/Cougar XR-7 IRS rears (?). As I mentioned, my IRS came out of an early supercharged V-6 T-Bird and doesn't have the aluminum lower arms.

Possibly V-8 models had them and V-6 models didn't or, possibly all models were changed over at a later date. Who knows?

I'm not certain when the Thunderbirds/Cougars went from the 5.0L engine to the Modular 4.6L but if it was like the Mustangs, the 5.0L engine was dropped at the end of 1995 and the 4.6L took its place beginning in 1996.

[oldandbroke]

Checked under the hood before I jacked it up.
It is an 8.8 aluminum, lower arms.
I am concern about the ratio, tag says 27 ?????

[ultraranger]

Checked under the hood before I jacked it up.
It is an 8.8 aluminum, lower arms.
I am concern about the ratio, tag says 27 ?????

The bolt head that's holding the tag on is covering up the first part of that string. The ratio would be a 3.27. IF there is an "L" between the 3 and the 27, then it has a Traction-Lok differential.

[oldandbroke]

Your are right, it is a 327, but no L. I was hoping for the L, but just not that lucky.
Have not cleaned it as yet. As a matter of fact I have not got it out of my trailer yet.
It does have aluminum lower arms, and appears to be an aluminum case.
I may have screwed up when getting it, I did not get the full length of the emergency brake cable..

I have lots of trees to cut up from the ice storm, so it may take me a few days to get back to it.

Thanks for the input

[elgemcdlf]

Putting in Trac Loc is no big deal. You need to find a Trac Loc from a 28 spline. Ford Ranger or CV (police car) and of course any of the IRS units with possible exception of the Cobra. The spyder gears are slightly different between a solid axle & the IRS. I had mine machined to match IRS gears.

[ultraranger]

Putting in Trac Loc is no big deal. You need to find a Trac Loc from a 28 spline. Ford Ranger or CV (police car) and of course any of the IRS units with possible exception of the Cobra. The spyder gears are slightly different between a solid axle & the IRS. I had mine machined to match IRS gears.

Another possibility for a Traction-Lok differential from a wrecking yard donor would be from any 1986-to present Mustang GT. All Mustang GTs come standard with 8.8" Traction-Lok differentials. --you would have to mod the axle gears, as elgemcdlf mentioned. Another potential wrecking yard source for a Traction-Lok would be Ford F-150s and Explorers. Not all of these last two have Traction-Loks but they do tend to have better ratios; 3.31, 3.55, 3.73 or 4.10:1.

...forgot to mention; Ranger pickups from 1991-earlier had 28-spline axles. Also beware that some of the early Rangers had 7.5" rear ends. 1992-later model Ranger 8.8"s went to 31-spline axles. F-150 and Explorers would have 31-spline axles as well. However, the 31-spline axle gears can be swapped in the Traction-Lok differential and vise-versa.

[elgemcdlf]

Putting in Trac Loc is no big deal. You need to find a Trac Loc from a 28 spline. Ford Ranger or CV (police car) and of course any of the IRS units with possible exception of the Cobra. The spyder gears are slightly different between a solid axle & the IRS. I had mine machined to match IRS gears.

Another possibility for a Traction-Lok differential from a wrecking yard donor would be from any 1986-to present Mustang GT. All Mustang GTs come standard with 8.8" Traction-Lok differentials. --you would have to mod the axle gears, as elgemcdlf mentioned. Another potential wrecking yard source for a Traction-Lok would be Ford F-150s and Explorers. Not all of these last two have Traction-Loks but they do tend to have better ratios; 3.31, 3.55, 3.73 or 4.10:1.

I do not know about the F150 but Explorers are 31 spline. The inner joints on the IRS are 28 spline. No idea on what the Mustangs had for axles (spline).

[ultraranger]

Putting in Trac Loc is no big deal. You need to find a Trac Loc from a 28 spline. Ford Ranger or CV (police car) and of course any of the IRS units with possible exception of the Cobra. The spyder gears are slightly different between a solid axle & the IRS. I had mine machined to match IRS gears.

Another possibility for a Traction-Lok differential from a wrecking yard donor would be from any 1986-to present Mustang GT. All Mustang GTs come standard with 8.8" Traction-Lok differentials. --you would have to mod the axle gears, as elgemcdlf mentioned. Another potential wrecking yard source for a Traction-Lok would be Ford F-150s and Explorers. Not all of these last two have Traction-Loks but they do tend to have better ratios; 3.31, 3.55, 3.73 or 4.10:1.

I do not know about the F150 but Explorers are 31 spline. The inner joints on the IRS are 28 spline. No idea on what the Mustangs had for axles (spline).

All Fox Mustang GTs from 1986-1993 had 8.8" rears with 28-spline Traction-Lok differentials as standard equipment --but generally not good ratios; most common would be 2.73 or 3.08:1. I'm not so certain on the SN95 (1994-2004) Mustang GT 8.8" rears if any had 28-spline and some had 31-spline or, if they all switched to 31-spline (?). In the case of my 2003 Mustang Mach 1, it has a factory 8.8" solid axle housing with a Traction-Lok differential, 31-spline axles and a 3.55:1 ratio.

....but again, if the Traction-Lok differential has 31-spline axle gears, they can be swapped out for 28-spline gears (and vise-versa).

Another option is to just buy an 8.8" 28-spline factory Traction-Lok differential off ebay. They are generally pretty cheap.

[elgemcdlf]

....but again, if the Traction-Lok differential has 31-spline axle gears, they can be swapped out for 28-spline gears (and vise-versa).

Another option is to just buy an 8.8" 28-spline factory Traction-Lok differential off ebay. They are generally pretty cheap.

As one who swapped in a Trac Loc once you find the 28 spline spyders you have found the entire unit. I checked with Ford but was unable to produce gears. Most likely due to age. I looked right at a 28 spline unit & did not realize it at the time. I bought a 31 spline unit from an Explorer thinking I will just swap out the gears with my open unit. Nice try! Not the same so then the search was on for 28 spline spyders. I ended up putting an ad on Craigslist offering the 31 spline unit with 4.10 gears for sale or trade. The only guy that responded had a 28 spline unit from a Mustang with 3.55 gears that wanted to swap to 31 spline. Swapped straight across & all was good.

[oldandbroke]

Thanks for all the info guys. I am taking notes for future reference.
Sorry about slow to post reply.
Got transmission out, and cleaned, will be rebuilding. Removed exhaust manifolds, only broke 4 bolts, fourth one I just cut the head off.
So 3 have some bolt sticking out, tried liquid wrench, heat twice, no luck so for. got some bolt grippers. Going to give that a shot. Next will be pulling heads.
Guess I should start a build thread...