2.88 LSD on '97 XJ6
#1
2.88 LSD on '97 XJ6
From what I've read, the 2.88 LSD diff from an XJ40 will fit my '97 XJ6, however, I am wondering how to calculate and figure the change in RPM's and if it will be a smooth crossover drive ability wise. Has anyone done this?
I'd like the benefit of the LSD plus the lower gears will help fuel mileage no? Or do I have that backwards and the lower 2.88 will spin faster than the stock 3.58 I have now?
I'd like the benefit of the LSD plus the lower gears will help fuel mileage no? Or do I have that backwards and the lower 2.88 will spin faster than the stock 3.58 I have now?
#2
I found this site:
Differential Gear Ratio Calculator | West Coast Differentials
I did some calculations based on my 225/60R16 tires @ 26.63" diameter
2.88 gears = 1,908 RPM @ 75 MPH
vs
3.58 gears = 2,371 RPM @ 75 MPH
463 RPM less on the 2.88 it would seem, and therefore some level of fuel savings.
I am just concerned about the acceleration, performance, etc.
Differential Gear Ratio Calculator | West Coast Differentials
I did some calculations based on my 225/60R16 tires @ 26.63" diameter
2.88 gears = 1,908 RPM @ 75 MPH
vs
3.58 gears = 2,371 RPM @ 75 MPH
463 RPM less on the 2.88 it would seem, and therefore some level of fuel savings.
I am just concerned about the acceleration, performance, etc.
#3
#5
My Manual XJR X300 averages 18 - 20 mpg on my daily drive circuit, all conditions averaged.
My auto 3.2 averages 21-22 on same trip, again over a long cycle (eg a whole tank of gas, 300+ miles)
the XJR accelerates 80-120 km/h in 3rd gear in about 3.5 to 4 seconds
the 3.2 does 100-120 in about 3.5 to 4 secs.
Power and ratios seem to have minimal effects on economy of hauling an 1800kg car around. Having said this, the XJR has great propensity to drink a whole lot more fuel if the available power is used, and if so the performance is vastly better than the 3.2
My auto 3.2 averages 21-22 on same trip, again over a long cycle (eg a whole tank of gas, 300+ miles)
the XJR accelerates 80-120 km/h in 3rd gear in about 3.5 to 4 seconds
the 3.2 does 100-120 in about 3.5 to 4 secs.
Power and ratios seem to have minimal effects on economy of hauling an 1800kg car around. Having said this, the XJR has great propensity to drink a whole lot more fuel if the available power is used, and if so the performance is vastly better than the 3.2
#6
I believe the EARLY XJ40 (3.6 Liter engine) had the 2.88 Diff.
I think you will have trouble because that diff has the U joint flange type coupler as opposed to the JURID flange.
As long as the diff/propshaft couplers are compatible it should fit.
The 4 pinion end mount holes in the XJ40 diffs have a different thread pitch (M10X1.25 vs M10X1.5) than the X300 but that is really the only difference.
bob gauff
I think you will have trouble because that diff has the U joint flange type coupler as opposed to the JURID flange.
As long as the diff/propshaft couplers are compatible it should fit.
The 4 pinion end mount holes in the XJ40 diffs have a different thread pitch (M10X1.25 vs M10X1.5) than the X300 but that is really the only difference.
bob gauff
#7
Join Date: Feb 2014
Location: Crossroads of America
Posts: 19,673
Received 13,425 Likes
on
6,623 Posts
Our '88 XJ40 had a 2.88 diff with the Jurid flexible coupling at the input. What I don't recall is whether it was an LS or open diff.
The first thing I noticed when I purchased the '93 XJ40 with 3.58 diff was that accelleration off the line was MUCH better (part of that was the increased engine displacement, HP and torque, but I think most of it was the rear end). I think going back to a 2.88 would be highly disappointing unless you really don't mind slow starts.
The second thing I noticed was that the '93's engine ran nearly 500 rpm higher at all speeds, which is consistent with SD96XJ6L's calculations.
Cheers,
Don
The following users liked this post:
MountainMan (06-08-2015)
Trending Topics
Thread
Thread Starter
Forum
Replies
Last Post
baskervillema
XJ XJ6 / XJR6 ( X300 )
4
10-01-2015 06:43 PM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)