Jag rear gear changes?
 

I have an early series 1 jag rear with a 3.07. Anybody know if, what and how easily gear changes can be made? Suppliers of such gears or items? I would also like to hear from anyone who has performed such changes themselves as to the difficulty or suggestions. Thank you!

Hello Tony:
I too have been doing alot of homework on the Jaguar Series 2 rear gear change process. I would assume this info does apply to your series 1 rear, but an not knowledgable in those particulars. I have an ERA with 4.11 rear gears. It is a real slingshot off the line. However at 3000 RPM in 4th I am doing 61 MPH so my top end suffers.

Now for the process that I have found out about...

The changing of the rear gears is bench work. It requires dial indicators and some finesse to do the set up. Thus, virtually no one who does this work will do it in-situ. Translated... The entire rear suspension must come down and out.

Second, the center section of the rear suspension needs to be benched so the rear suspension must be dis-assembled. During the disassembly, you can, in theory, replace worn parts or those that need refreshing.

I hear that once you have the center section out, the best process is to totally replace it with a center section that already contains the gearing and LSD that you desire. You just keep your old one as a spare. Thus what you are looking for then is a back up center section from a similar JAG rear that you have now.

There is a firm called Reider Racing www.reiderracing.com. They specialize in rebuilding such JAG center sections and rebuilding the LSD and setting it all up. Certain Cobra firms use Reider to do all their work. The typical going rate today for a junkyard center section from a correct Jag Series 2 is now in the $500-700 range without shipping costs, i dunno if your Series 1 would be more or less, probably the former. I have no idea what the fee is that Reider would charge to deinstall and reinstall correct gearing. They can tell you that. I do not wish to speak for them as prices I have are for series 2 not 1.

So the course of action as I see it is.... one of two choices. Upgrade your current center section or get a second and have the gears and LSD made right. The bene of the second choice is that you have a spare on the bench and you can shorten downtime of the car by having it all ready prior to starting the rear suspension pull.

I am still, personally, very very torn over doing this procedure. My 4.11 rear gears make my Cobra a rocketship from standing start and although my engine is busy at 60 MPH plus and I have given up high end top speed, the car is a heck of a lot of fun to drive.

My other option is to go with a 5 speed trannie and pull out the close ratio Toploader. I have not made up my mind. My 428 is a torque monster, especially between 2800 and 5200. Nearly a flat torque curve at 435-445 ft/lbs, as currently set up, with mufflers, in car, air filter, etc on the chasis dyno.

I hope this long winded response helps??

Cheers

what years did the series 2 diff. entail? thanks;chuck

Well, The Series 2 Jaguar Differential was on the XKE from 1964 thru 1974 as well as the 1965 thru 1983 Jaguar XJ-6. Sometimes, the year code is punched in the casting on the lower right corner of the cover. The year code is the top number on the cover. These are getting to be harder to find now.

Also, there is often a small metal tag present on one of the rear cover bolts. This tag has numbers on it. If the tag says 43/13 then this means it is a 3.31 ratio gear, 43/54 means 3.54 and 44/11 means 4.11 gears. This tag is not always present due to maintenance. Jags XKEs in the 1961-64 time frame almost always had 3.31 gears but then to meet emissions standards in the USA, the car was detuned, lost torque, and so to keep the feeling of performance, the rear gears were changed to 3.54. Those are often found in 1964-1970 rear ends. Some of the automatic cars had even higher ratios. That is about all I know about this.... Does anyone else have any more info???

The series 2 rear typically has inboard brakes. I have been told by some Jag experts, that there are some variances in the brake holes in some rear center sections. I am not well versed in that aspect. These rear ends can take about 500 BHP, however the drive shafts and such have to be in good shape to do that. I would never suggest poping your clutch with really high RPMs and a hot engine. There are some horror stories here with blown components in the rear from such misbehaviors. :CRY:

Cracker,
I sent you an IM. My friend has 3.54s in his car and wants to go to 3.08. His is the early jag center section. If you are looking to go to lower gears (like 3.54), I will talk to him today. He's taking it over to get the gear swap this week or next week.

hi cracker jag diffs are 2.88 mostly autos 3.07 for 4 speed box 3.31 5 speed v8 3.54 ,here in uk 3.31 is the most popular with chevy 350 or 351 ford also rover 3500cc[ small buick ] ihave 351 cleveland zf box 3.31 diff 17in hallibrands , diff came out of xjs lots of rotten jags in uk .look at www.ward-engineering.co.uk for crown wheel and other jag bits .i have a 1941 step side chevy pick up to restore after cobra finished cheers

Jag IRS and Diffs
 

If youre after chapter and verse on Jag ratios and such, post a question or do an archive search, at the UK Cobra club site at www.cobraclub.com .

Most high power cobras ( ie most with V8's) are built here with Jaguar IRS and theres a wealth of knowledge to be tapped.

Most Jags in UK came with a 3.31 non Powerlok (Limited slip diff)as standard ( check the tag on the diff itself to check) so if you're after a high ratio powerlok look for a XJS as a donor as all XJS had powerlok.

We have quite a few people using jag diffs with high output engines , Drag racers included, and a properly set up diff should be able to handle in excess of 500BHP regularly.

I would suggest doing a search on Jag Diffs at the UK site and all will be made clear.

Cheers,

Tony


:)

Two Pack, I'm going the other way. Restoring my 37 Chev Pickup before I tackle a Cobra. Mostly because I got it from family and it's been in our family for 63 years