3.07 Ring gear won't fit in 2.88 Case

I am posting this because I have not been able to find the answer to solve my problem. I purchased a PL Differential that has 2.88 gears. I think it is early XJS but I am unsure. I have a set of 3.07 gears that I bought many years ago and wanted to build this unit for my Series II E-Type roadster. I took the Diff and gears to a Local driveline shop to be fitted. The owner called an told me the 3.07 ring gear is thinner than the 2.88 and cannot be shimmed out enough to make it work. He told me that there must be a Brake in the Diff Cases and to find the correct case for these gears. I still have the original 3.54 diff in my E-Type and have the rear end out of the car. My question is: Is there a difference in the 2.88 case from the 3.54 and will the 3.07 gears fit in the 3.54 case? Hope someone knows. Thanks

@Dick_Maury will know.

Well the entire 2.88 diff fit? I Love my 2.88.


Hi James, I did convert my 66 FHC to a 3:06… Dick Maury did the conversion. My 65 OTS still has the 3:54. Since I did the conversion, I did have the chance to drive a 3.8 OTS with the 5 speed and that is the way to go. I know that is the most expensive conversion, but it was really awesome to drive. Norman Dewis`s favorite was the 3:31.


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So many variances on diffs over the years. The cases vary in the bearing size for the races. The carriers that hold the ring gear vary in height at the position where the base of the gear is mounted. The pinion gear varies depending on if it is an earlier one with shim adjustment or a later one that uses a crush sleeve. The whole 2.88 diff assembly will bolt right in your Series 2 without any modifications. There is not enough of a difference between the 2.88 and the 3.07 to worry about. I always get a chuckle when advice is given to just take it to someone that works on Jeeps.


Thank you for the quick response. The Driveline guy told me that the new 3.07 ring gear is about 1/4 inch thinner than the 2.88 ring which I noticed myself. Do you think the 3.54 Diff that is in my series II now has the correct case for this 3.07 gear set? I heard that there was a brake in size when the ratio is taller than 3.07.

Variables here. Is the upper area of the pinion gear the same diameter between the different gears? Do you have a later 3.07 set that uses a crush sleeve or one that uses shims? You can make a 1/4" spacer and use longer bolts if that is the only difference. However, as mentioned, a lot of effort for very little gain over just using the 2.88

The 3.07 Pinion is the same size and uses a crush washer and also has shims under the pinion bearing. I read that the 2.88 is very tall for the E type and would not be a good set for varied driving. I have a 2+2 also with a 3.54 and it screams at 75 MPH so this is why I am interested in the 3.07 change.

Shims do not normally go under the pinion bearing. As mentioned, there is very little difference between the 3.07 and the 2.88. Not sure where you read that the 2.88 was to tall. I have put them in 6 cylinder XKEs and V12s with no driving issues. The 2.88 was used in the XJ6 with a 3 speed automatic and the car was much heavier. You have a 2.88 that will bolt in with no modifications. Lots of effort to convert the 2.88 to a 3.07 without much gain. Best of luck with whatever you decide on.

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Dick, Thank you for the input. I may just do that. I hate to crack open a perfectly good 3.54 when I could just toss in the 2.88 and try it. I have restored this car to perfection and have not even driven it yet so I need not sweat this anymore. I like what you said about the 2.88 being a good ratio so I will give it a go. I will let you know how it works out. Cheers!

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When I installed my 2.88 I changed the right angle gearbox on the back of the transmission to a different ratio so the speedometer would read correctly. I ordered this custom made right angle box from the UK. You also can buy adapters in the US that will change the ratio if you send them your speedometer cable.

I have a 2:88 (from Dick) and live in San Francisco. I LOVE it. It makes first gear actually usable and 2nd is a great back roads gear. The only marginal difference is if you’re pulling hole shots racing minivans at stop lights. You’ll get beat either way but perhaps by 5 feet less with the 3:07…


Winning a hole shot against a minivan is like winning a tallest midget contest.

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Tferrer, thank you for response! I have decided to tell the Driveline shop to put in the original 2.88 set and try it. it is a 70 OTS and I think it will be a nice change from the 3.54 in my 2+2. I only use 3rd and 4th in that car and it runs out of gear quickly even with the 205 75s. I am way past the racing minivan days but do enjoy the West Virginia winding byways. Cheers!

I think you will really love the 2.88. I had a 3.07 in my '63, and even living at my altitude and going through mountains passes, some close to 14,000 feet, I never had any issue with it.

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Yup. Same car. 70 OTS