? rear axle ratio change for more low end performance
#1
? rear axle ratio change for more low end performance
Several members with first generation XKRs (v8) changed their rear axle ratio to achieve more low-end performance/pull. It came at the expense of highway mileage but was cited as even more effective than supercharger pulley upgrades for acceleration from a dead stop. For the pre 2003 XKR models with the Mercedes transmission, additional re-programming was required at $2,000 by itself so only a handful of owners went that far. I think everyone who did rear axle ratio changes also did supercharger upgrades as well as limited slip differentials so quite the expensive package of upgrades.
Is X300 4.0 litre inline six sedan amenable to a simple rear axle ratio change or are their enough complicating factors that it's simply too much money considering the value of the car itself?
Is X300 4.0 litre inline six sedan amenable to a simple rear axle ratio change or are their enough complicating factors that it's simply too much money considering the value of the car itself?
#7
This should be an interesting cost proposition compared to nitrous via the Wizards of NOS supplier in U.K. and the V8 conversion from JaguarSpecialties.com in CA USA.
So, I change the ratio and retain the existing differential without adding the XJR's LSD "Posi" unit as well? Local Jag mechanics here in Denver CO are very conservative so I have to present this well up front, despite being a 45 year old guy.
So, I change the ratio and retain the existing differential without adding the XJR's LSD "Posi" unit as well? Local Jag mechanics here in Denver CO are very conservative so I have to present this well up front, despite being a 45 year old guy.
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#8
Gonna be hard to find in the USA as Jaguar used them in the smaller (3.2 litre) engine cars. But perhaps a dealer or Jag parts specialist can order/find a set for you.
Cheers
DD
#9
This should be an interesting cost proposition compared to nitrous via the Wizards of NOS supplier in U.K. and the V8 conversion from JaguarSpecialties.com in CA USA.
So, I change the ratio and retain the existing differential without adding the XJR's LSD "Posi" unit as well? Local Jag mechanics here in Denver CO are very conservative so I have to present this well up front, despite being a 45 year old guy.
So, I change the ratio and retain the existing differential without adding the XJR's LSD "Posi" unit as well? Local Jag mechanics here in Denver CO are very conservative so I have to present this well up front, despite being a 45 year old guy.
Not really sure what you're asking, sorry.
Cheers
DD
#10
Your answer is helpful as to what may be realistic for Coventry West or Jaguar Heaven to be able to provide/find. Now I realize neither may have access to what I am seeking since both are in the USA here. Guessing overseas source is going to be far more expensive. Thanks.
Andy's bracket just arrived today so that may be it for a while if additional options all come to 1/2 if not the full value of the car itself.
Andy's bracket just arrived today so that may be it for a while if additional options all come to 1/2 if not the full value of the car itself.
Last edited by weisberg; 10-29-2014 at 09:17 PM. Reason: tense of a word
#11
Doesn't take a lot to squeeze a bit more out of these engines without expensive mods. Depends how much fire you really need to create. The 3.2 is effectively the same engine as the 4.0 n/a, but with a shorter stoke. Fitting Andy's bracket plus a direct air intake has pumped my super-smooth 3.2 up appreciably on acceleration and I can't really tell much difference between it and a 4.0 that I occasionally get to drive. Since you are used to a n/a engine, you might find that these 2 simple mods will keep you satisfied without the big $$.
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weisberg (11-01-2014)
#12
I think it would be fun to change the rear end gearing IF one already had a need to repair the rear end. ...or one has a bunch of $$ lying around and the XJ is their hobby car
Mine is a daily driver, so I'll likely never change the rear end, but if I have to and it is still worth it... I'll definitely consider the XJ6 3.58 gearing.
Mine is a daily driver, so I'll likely never change the rear end, but if I have to and it is still worth it... I'll definitely consider the XJ6 3.58 gearing.
#13
#14
Coventry West can do rear axle ratio change
Bryan Barnett at Coventry West has confirmed they can provide the parts.
A 4.09 "power-lock" (LSD) differential is $995 with no core charge or need to ship the existing 3.58 core back to them. So I could achieve the stronger off the line performance and get the LSD that would make cornering more fun. There are slightly less expensive alternatives that involve shipping the 3.58 core back to them although shipping of $100 (approx.) back to them makes that a debatable use of time and effort.
Changing the ratio only (no LSD) is not a cost saving effort.
It appears doing this is a $2,000 project. While that is half the price of the car, it is still cheaper than buying a different car. Gives me a nice goal to shoot for by the Spring!
A 4.09 "power-lock" (LSD) differential is $995 with no core charge or need to ship the existing 3.58 core back to them. So I could achieve the stronger off the line performance and get the LSD that would make cornering more fun. There are slightly less expensive alternatives that involve shipping the 3.58 core back to them although shipping of $100 (approx.) back to them makes that a debatable use of time and effort.
Changing the ratio only (no LSD) is not a cost saving effort.
It appears doing this is a $2,000 project. While that is half the price of the car, it is still cheaper than buying a different car. Gives me a nice goal to shoot for by the Spring!
#15
Is that the cost of an entire rebuilt differential, or just the gear set?
I think this would be a fun modification to put the 3.58 LSD in my XJR and get better off-the-line performance, but in my case I can't really justify the cost since my rear end is still good and I do 90% highway driving so MPG impacts do add up.
Keep us up to date on the project, especially with regard to cost, difficulty, lessons learned, etc
.
I think this would be a fun modification to put the 3.58 LSD in my XJR and get better off-the-line performance, but in my case I can't really justify the cost since my rear end is still good and I do 90% highway driving so MPG impacts do add up.
Keep us up to date on the project, especially with regard to cost, difficulty, lessons learned, etc
.
Last edited by al_roethlisberger; 11-15-2014 at 10:13 AM.
#16
That is the entire rebuilt differential. Coventry West's Bryan Barnett said it is not complicated "but that it does take a good bit of work to get the old one out and the new one in".
Now that I know this option (probably the best for my driving priorities), time to figure out nitrous oxide versus V8 from JaguarSpecialties (Andrew).
Now that I know this option (probably the best for my driving priorities), time to figure out nitrous oxide versus V8 from JaguarSpecialties (Andrew).
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