Jag IRS rear ratio change

[Cwright99]

Looking for information on changing the ring and pinion on a Jag IRS. My current Cobra set up is a 429 SCJ (550 HP), CR Toploader and a 3.54 gear ratio in a 61-63 XKE Jag IRS.

Trying to get a sense of how difficult it is to change out the ring and pinion to 3.08 or something along those lines. Is this relatively straight forward like changing the gears out of a standard non IRS rear end. Or is it far more complicated and should be left to a professional.

[Grubby]

It is essentially a Dana 44 differential. Same as used in Jeeps and many American cars. Pretty straight forward to work on.

Be careful, there are some differences. For example the ring gear uses different size bolts than a Dana 44. Do your homework before starting.

John

[RICK LAKE]

The Jag rear center section is basical a Dana 44 center section. As far as the ring and pinion, it's not a direct bolt on change. The Dana 44 like jeeps have uses different ring bolts and bolt pattern than a Jag carrier. Can you swap over, Yes with some machine work. I have done this for my rearends. You didn't say which stub axles do you have? 17 or 19 spline, or 27 spline stub shafts. The best thing would be for you to find another center section and sell this one or keep for a spare. Something else is that this Jag rearend is only good for about 450/450 HP and torque. This is with a street tire of 200 or higher wear. Run a softer tire or high power motor and you are looking at running a rearend carrier with 30 spline stub shafts, differential cover with support bolts for controling carrier cap walk. With the extra work you can up the power rating to 600/600. Chromemoly short shafts and running a 30 spline locker would be recommended. Rick L.

[Tom Wells]

Cwright99,

Here's a little insight into the Jag version of the Dana center section: DazeCars, Mustang IRS or Independent Rear Suspension page IV

Only you can decide if you're up to the task!

Tom

[puttputt]

Originally Posted by RICK LAKE

The Jag rear center section is basical a Dana 44 center section. As far as the ring and pinion, it's not a direct bolt on change. The Dana 44 like jeeps have uses different ring bolts and bolt pattern than a Jag carrier. Can you swap over, Yes with some machine work. I have done this for my rearends. You didn't say which stub axles do you have? 17 or 19 spline, or 27 spline stub shafts. The best thing would be for you to find another center section and sell this one or keep for a spare. Something else is that this Jag rearend is only good for about 450/450 HP and torque. This is with a street tire of 200 or higher wear. Run a softer tire or high power motor and you are looking at running a rearend carrier with 30 spline stub shafts, differential cover with support bolts for controling carrier cap walk. With the extra work you can up the power rating to 600/600. Chromemoly short shafts and running a 30 spline locker would be recommended. Rick L.

Thanks Rick, I am in Australia and have ordered a new Dana 44 30 spline locker from the USA.

But where can I get the chrome moly short shafts from ?

Cheers,

Puttputt

[puttputt]

I hope I didn't hijack thread with my last question ?

[RICK LAKE]

puttputt Info is going to cost you a first name. Here's the problem, I got my parts from CWI back in 1998. You got shafts, and side gears for a dana 44 to change from 27 spline to 30 spline. It was a nice kit but cost 1K and no warrantties if you built the rearend yourself. The shafts came from, guess where??? Down under. Come to understand that they where not up to spec and guys where twisting them. The kit was for 600/600 of power. Your company down under is either out of bussiness or not producing them. My shafts came from your end of the world. I have raced and auto crossed for years and no failures. I have also limit the tire softness of a 200 wear. I believe that this has saved the Jag rear and shafts from twist or snapping off. My tires go up in smoke and will not grip well with 620ft torque. I also don't do 5,000rpm clutch drops to impress friends.
The only info I have is to try Williams axles here in US. I believe he is making them and was at the end when CWI was still in bussiness. They make custom shafts, but not cheap. Also used the correct chromemoly spec steel. Good luck, if you need any more info I will try and help. Rick L. Ps is Fosters any good??

[Anthony]

Originally Posted by Cwright99

Looking for information on changing the ring and pinion on a Jag IRS. My current Cobra set up is a 429 SCJ (550 HP), CR Toploader and a 3.54 gear ratio in a 61-63 XKE Jag IRS.

Trying to get a sense of how difficult it is to change out the ring and pinion to 3.08 or something along those lines. Is this relatively straight forward like changing the gears out of a standard non IRS rear end. Or is it far more complicated and should be left to a professional.

If you are going to change to a 3.08, then you'll need to change your tranny from a CR to a WR to make those rear gears work, otherwise, to simulate what it'll be like, try to always start your cobra from a stop in 2nd gear. That'll give you an idea.

If you change gears, you may just want to buy another completed center section, and change it out, selling your old one, or keeping it as a spare.

If you're not going to change your tranny, I'd leave it alone.