irs 8.8 question

[vector1]

looks like the 8.8 irs has different rear covers that use different mounts. are these covers interchangeable without changing any of the gear setup? i'm looking at a rear end but don't believe it has the same cover style and wonder if they interchange.

also, if the present setup is 3.27 ratio with ls, can this be changed to a 3.73 or higher ratio using the existing parts and changing the r & p only?

thanks

[priobe]

Victor1,

I recent changed my gears from a 3.73 to 3.27.

So yes it can be done.

Regarding the cover, becareful because the cover foor the live axle 8.8 will fit also. But then you will not have any way to mount the back section of the diff.

[cobra bill]

In one of my projects I used a dif cover from an independent rear end on a live axle, and cut away and ground off and smoothed and polished one of the ears on the cover and used the one mounting ear left as a panhard bar mount, it looks great and worked really well.

[LMH]

Here's the cover I have. Stock cover isn't very strong.
Larry

[LMH]

Every 8.8" IRS cover that I've seen that came from either a T-Bird or Mustang, looked the same. Not saying there aren't different ones, just that I haven't seen them. Mustang/T-Bird differentials have symetrical mounts at the nose and one in the rear.
Explorer's have a different style mounting system and the differentials look different though I beleive they use 8.8" internals.
Larry

[vector1]

i have one irs with the cover pictured above, i have another irs that has a horizontal mounting platform on the cover. i am wanting to replace the irs with the horizontal mount with another irs, and i don't know which cover the irs i'm looking at uses until i get pics, which is why i am wondering if they can be interchanged, along with the gears.

i believe the tbird unit is the vertical mount, would the horizontal mount be the cobra?

the one i'm looking into is from a 99 cobra, which i understand has the 28 spline inner and outer half shafts which i need and is aluminum, don't know if it is ls yet, but has a 3.27 gear ratio which needs to be changed.

thanks

[eschaider]

If you are using the 8.8 IRS center section you ought to give serious consideration to this cover. It is in my opinion the best cover solution for Ford's 8.8

Here is a view from behind:



Here is an oblique side view:



And a view from low and behind:




Yes, it is billet and it is manufactured by ForePrecision. It fits into the near indestructible category. There are nice special touches like inlets ond outlets for a differential oil pump/cooler, load bolts for the differential caps etc. This is their website click here=> http://www.foreprecisionworks.com/0058-200.html It starts life as a 55 lb billet of 6061 and looses 44 lbs on a CNC diet. You can order it through LethalPerformance, click here => http://www.lethalperformance.com/03-...-cover-p-28522

The stuff Fore manufacturers is reminiscent of the Kirkhams - all top shelf and very high quaity.

Ed

[LMH]

Originally Posted by vector1

i have one irs with the cover pictured above, i have another irs that has a horizontal mounting platform on the cover. i am wanting to replace the irs with the horizontal mount with another irs, and i don't know which cover the irs i'm looking at uses until i get pics, which is why i am wondering if they can be interchanged, along with the gears.

i believe the tbird unit is the vertical mount, would the horizontal mount be the cobra?

the one i'm looking into is from a 99 cobra, which i understand has the 28 spline inner and outer half shafts which i need and is aluminum, don't know if it is ls yet, but has a 3.27 gear ratio which needs to be changed.

thanks

My differential is from a 2004 Mustang Cobra SVT. It's all aluminum, 31 spline 3L55. I assume the 99 Cobra has the same mounting but I'm not 100% sure of that. I would think the covers would be interchangeable though. Does it have the same front mounting ears as the T-Bird/Mustang unit?
Larry

Nice cover Ed!! Wish I had known about that one before I bought mine. I like the cooler ports.
Larry

[vector1]

that is some nice stuff. i was looking at control freak stuff and it said this

*****WILL NOT FIT 1999-2004 Mustang Cobra with IRS***** T-Bird Supercoupe Cougars with 8.8" IRS Rears Lincoln MK VII & VIII IRS Applications

so it looks like some of the stuff will not interchange, different bolt holes somewhere.

then another place it looks like 1989-1997 T-Bird,1993-1998 MK-VIII, and 1999-2004 Mustang Cobra are the same.

i think what i am looking at will work i just did not want to get into interchangeability problems and be stuck with something i can't use.

[eschaider]

Originally Posted by LMH

My differential is from a 2004 Mustang Cobra SVT. It's all aluminum, 31 spline 3L55. I assume the 99 Cobra has the same mounting but I'm not 100% sure of that. I would think the covers would be interchangeable though. Does it have the same front mounting ears as the T-Bird/Mustang unit?
Larry

Nice cover Ed!! Wish I had known about that one before I bought mine. I like the cooler ports.
Larry

I know what you mean Larry. They just came out with it about a month ago. It's definitely impressive and like yourself I really appreciate the provision for the use of a cooler.

Originally Posted by vector1

that is some nice stuff. i was looking at control freak stuff and it said this

*****WILL NOT FIT 1999-2004 Mustang Cobra with IRS***** T-Bird Supercoupe Cougars with 8.8" IRS Rears Lincoln MK VII & VIII IRS Applications

so it looks like some of the stuff will not interchange, different bolt holes somewhere.

then another place it looks like 1989-1997 T-Bird,1993-1998 MK-VIII, and 1999-2004 Mustang Cobra are the same.

i think what i am looking at will work i just did not want to get into interchangeability problems and be stuck with something i can't use.

vector1,

With one exception (I think the Explorer) all the aluminum ones are the same. The ones for the cars use various different anchoring techniques on the rear cover depending on the car they came from. The Cobra style anchor is among the strongest. What you see on the billet cover is the Cobra style rear anchor.

The rear cover is the first weak spot because it is not only a casting but a thin casting. The billet approach fixes that problem.

Ed

p.s. if you can't find a Cobra unit be sure to change the side gears in your piece to the 31 spline Cobra pieces. You'll be glad you did.

[LMH]

Originally Posted by vector1

that is some nice stuff. i was looking at control freak stuff and it said this

*****WILL NOT FIT 1999-2004 Mustang Cobra with IRS***** T-Bird Supercoupe Cougars with 8.8" IRS Rears Lincoln MK VII & VIII IRS Applications

so it looks like some of the stuff will not interchange, different bolt holes somewhere.

then another place it looks like 1989-1997 T-Bird,1993-1998 MK-VIII, and 1999-2004 Mustang Cobra are the same.

i think what i am looking at will work i just did not want to get into interchangeability problems and be stuck with something i can't use.

One thing that I found was that while it says "won't fit", that tends to apply to production cars and how the diff mounts in the car. For me, that didn't apply as I was making mounts for the differential myself. The cover may bolt on to the diff just the same.
Larry

[vector1]

that's what i was looking for ed.

i have one that has the cobra style cover, the other is the one i'm looking to replace and it is different, it must be an explorer style i'm guessing? all the front two ears are the same, the rear on the explorer unit sits on a shelf it looks like with a support mount.

so it looks like i'm trying to replace a cast iron explorer unit with a 99 cobra aluminum 8.8 with 3.27 and ls into which i would like to put a 3.73. anybody know how this will come out? sounds like the covers will interchange, i'll bet the spline count on the two are different.

did some searching, looks like the explorerer has 31 spline inner, 99 has 28 spline inner=too much work=keep looking.

[eschaider]

vector1,

Play around with some of the gearing calculators here and elsewhere. A 3.73 is going to produce a lot of engine speed at highway speeds even with an OD transmission like a TKO or T56, although a T56 would be better.

The other issue with a 3.73 is the launch. First gear will be all but useless. You will light up the tires even from a roll. A 3.55 is better but you may just be surprised how good a gear somewhere around 3.30 really is. So don't throw out the 3.27 as a useless ratio.

Last comment. If you haven't yet gotten your transmission look at the new T56 Magnum from Tremec. It is rated for 700 ft/lbs of Torque but more importantly has great ratios and triple cone synchronizers that make speed shifting a breeze.

Of course if you are like the rest of us and never flex your snake's muscles in front of women and children then the speed shifting thing is just so much nonsense. Of course, on the other hand ...

Ed

[eschaider]

vector1,

Forgot to post up the appearance of the cover from the inside. here is what it looks like:



Ed