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7/19/2016 1:30 am  #1

1988 4.2 sovereign ratio??

I have been offered a really cheap 1988 4.2 sovereign irs..guy cant tell me the ratio, i am hoping its not a 2.88 and if it is..what are my ratio options..i would prefer 3.3 up to 3.5 ish as im running a 308 cube aussie Holden motor ( built for torque) and 700r4 combo with 28 inch tall tyres in a heavy buick..Problem is the diff is approx 600 miles from where i am and id prefer not to do a huge trip if its a 2.88. I have done the google thing with conflicting results. Anybody able to help me on this one?


7/19/2016 10:36 pm  #2

Re: 1988 4.2 sovereign ratio??

If this is still a Jag rear, the ring and pinion are a Dann 44 design and they can be replaced with any ratio between 2.88 and 3.92. Anything over that and you need a different sized carrier. An experienced shop should be able to do the gear change for 300-350 plus the gears.


7/20/2016 12:44 pm  #3

Re: 1988 4.2 sovereign ratio??

There should be a tag on the rear that will give you the ratio.
In the U.S. it would almost certainly be 2:88 but other countries may be different.

At these prices I want my gas 100 octane, leaded, and my windshield washed!

8/03/2016 4:13 pm  #4

Re: 1988 4.2 sovereign ratio??

Thanks to those who assisted regards my questions on the 88 sov IRS diff..took the plunge and drove 600 miles to look at it, turned out to be a 3.54 ratio and an lsd !! Nice to have a win sometimes!! The guy selling it was a true gentleman, there was no tag on the cover alluding to  ratio etc but he stuck to his listed price  ( $ 175 aust ) and was really helpfull getting it loaded up with me. At this point it is trial fitted to my modified 47 buick chassis, it is looking like its going to mount up fairly easily and give me the ride height and travel i need and room for exhaust etc that was compromised with the cage type IRS . Im using all the factory mount points in both my front and rear Jag installations to minimise NVH . Now to track down some rear shock absorbers on this side of the pond and get to fabricating.


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