I went from the 2.88 to a 3.31 and the improvement is very apparent. I like it.

Not sure if 2.88 to 3.07 would be a big enough change to justify the effort, personally.

Cheers
DD

 

 

junkyard , some 6cylinder jaguars.

some had 3.54,, i run a 3.73 in mine ,with 700R4 overdrive!

 

Just keep an eye open on Ebay, Craiglist, the buy-sell section of this forum and others. Be ready to act quick. Typically they get snapped-up quickly.

I got super lucky and found mine in the classified section of Jag-lovers 5 minutes after beginning my search! The seller, who lives in Georgia, was even nice enough to personally deliver it to Coventry West for full overhaul. CW then shipped it to me.

Cheers
DD

 

 

6 and 12 cylinder cars used the same diffs....just different ratios. So no problem handling the V12 torque. They fit right in.

Cheers
DD

 

You need to make sure it is limited slip. A lot of 6 cylinder jags (sedans) used open diffs so just check you and the seller are on the same page.

 

Much depends on where you are, there are market differences as to what countries got LSD and which didn't. I wouldn't be in any hurry to grab a LSD over an open diff if it had the ratio I want. I'm not going to be driving my car in winter, so it makes no difference to me. I actually find in the wet the LSD makes the rear end quite twitchy in a V12, it's easy to kick the rear end of the car out if you want.

"Worth it" very much depends on your personal goals and what you like. If I was doing highway cruising I wouldn't want a lower gear ratio, especially with the 3 speed transmission. I had an E Type and went from 3.54 to a 2.88 specifically to get quieter highway cruise with less heat and better fuel economy.

 

 

You can definitely feel a difference.

No regrets. I might have regrets if I did lots of travel out on the open highway but, to be honest, the car is quiet enough that getting adjusted to the higher RPM isn't a big deal.

2500 RPM at 60 mph sounds about right.

You'll need to change the speedometer gears to get a proper reading.

Cheers
DD

 

For more remarks on the 3.31 diff see posts 15, 25, 48, and 54 of this thread

https://www.jaguarforums.com/forum/x...tinued-177670/

Cheers
DD

 

The standard 2.88:1 diff with the GM400 three speed gives 70 MPH at 2,700 rpm. Fuel consumption will be worse. My own view is that an LSD is pretty important for the XJS is you are going to use the acceleration from rest - which if you want a bit more it sounds like you do!
My car will scrabble for grip in the dry at full throttle take-offs with the 2.88 diff as it is.

 

 

Doug,

The speedo conversion sounds like a headache with the tranny in place and the drive pins etc.

Are you able to hunt down the drive pin part and give me a head start or give me a link to these parts if not much of a problem?

Cheers mate!

 

If you have the diff mounted speedo no conversion is needed, aside from making sure the new diff has the tone ring inside the housing. If it's a gear driven speedo, then it's the same as changing the gear in any Chevy TH400.

 

some times this can be a problem , to much torque , using 3.73 lsd gears, and 700R4 1st gear, but you learn to handle it!!

 

Yeah baby

 

OK, I check.. Cheers

 

I used a GM adapter #1565208. You'll have to find a used one. BUT, actually, you'd first need to calculate the amount of correction you need in your application and work from there.

The local NAPA auto parts store helped me with the drive pin dilemma....but I'm on my first cuppa coffee so the details are a bit fuzzy at the moment. I'll report back.

You definitely need a angle drive adapter. Not enough room between the transmission and the transmission tunnel for a straight one.

A slight PITA, yes....but it's all doable. Tons of stuff and info out there to correct speedometer readings. Here's just one example:

800 Series Speedometer Drive Train Correction Adapter

Cheers
DD