X100 XKR Differential Ratio Change
#1
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Hello all,
I have a 2000 XKR with the Mercedes W5A580 transmission. I've read from posts on this forum, that a differential ratio change is doable with a reprogrammed TCM. I've also read that such a TCM reprogramming (or reprogrammed TCM) is available at around $2K (it's worth it for me).
However, I have no idea where to go or who to contact for such a thing? Do you have any idea what direction to point me in?
Thanks for any help you can offer, Eric
I have a 2000 XKR with the Mercedes W5A580 transmission. I've read from posts on this forum, that a differential ratio change is doable with a reprogrammed TCM. I've also read that such a TCM reprogramming (or reprogrammed TCM) is available at around $2K (it's worth it for me).
However, I have no idea where to go or who to contact for such a thing? Do you have any idea what direction to point me in?
Thanks for any help you can offer, Eric
#2
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I imagine you are looking for a lower ratio? I remember reading that cars sold In Mexico had a lower ratio, nothing huge but definitely lower.
mind if I ask what prompted this? Do you want quicker off the line acceleration?
I bet just about all of us thought of this once or twice, especially those of us with normal aspiration.
it'll be quite a hunt given compatibility, availability, and programming issues, but I hope you have nothing but good luck.
John
mind if I ask what prompted this? Do you want quicker off the line acceleration?
I bet just about all of us thought of this once or twice, especially those of us with normal aspiration.
it'll be quite a hunt given compatibility, availability, and programming issues, but I hope you have nothing but good luck.
John
#3
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Hi John,
Yes, you are correct. I've done a number of HP upgrades over the years (SC porting & pulleys, cold air intake, exhaust & cats, etc.), so I'm happy with the motor. However, I like quickness and don't drive at really high speeds. Accordingly, I find the 3:06 stock rear end to be lethargic from a standstill.
Although it has been discussed a number of times on the various forums, my understanding is the naturally aspirated X100 models have a ZF 5HP24 transmission that does not facilitate a final drive ratio change as it would confuse the the TCM/ECM systems due to changes in the speed of some sensors while not changing others (wheel speed vs. others) and will consistently put the car into a "gearbox fault" status.
On the other hand, the SC X100 models (XKR), have a Mercedes W5A580 (722.6, NAG1) transmission that can facilitate this with a reprogrammed TCM (at least as is indicated in various forums).
My search is for a source for such a TCM reprogramming.
Eric
Yes, you are correct. I've done a number of HP upgrades over the years (SC porting & pulleys, cold air intake, exhaust & cats, etc.), so I'm happy with the motor. However, I like quickness and don't drive at really high speeds. Accordingly, I find the 3:06 stock rear end to be lethargic from a standstill.
Although it has been discussed a number of times on the various forums, my understanding is the naturally aspirated X100 models have a ZF 5HP24 transmission that does not facilitate a final drive ratio change as it would confuse the the TCM/ECM systems due to changes in the speed of some sensors while not changing others (wheel speed vs. others) and will consistently put the car into a "gearbox fault" status.
On the other hand, the SC X100 models (XKR), have a Mercedes W5A580 (722.6, NAG1) transmission that can facilitate this with a reprogrammed TCM (at least as is indicated in various forums).
My search is for a source for such a TCM reprogramming.
Eric
#4
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I have used a 3.2 liter XJ8 diff (3.27:1) (imported from Europe) on a customer car. I removed the 3 bolt JURID flange and cut the pinion shaft extension. I then used the 4 bolt 'U'joint flange from the XK diff.
It is easier to find a used 3.2 liter XJ8 from Europe than a XK diff from Mexico because of the sheer numbers manufactured.
They are both 'open-diffs' but you can install a 'tor-sen' or QUAIFE aftermarket limited slip to the crownwhleel.
A few forum members have had their TCMs recalibrated to the new ratio.
bob
It is easier to find a used 3.2 liter XJ8 from Europe than a XK diff from Mexico because of the sheer numbers manufactured.
They are both 'open-diffs' but you can install a 'tor-sen' or QUAIFE aftermarket limited slip to the crownwhleel.
A few forum members have had their TCMs recalibrated to the new ratio.
bob
#5
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