Upgrades: differentials and limited slip lockers!

[sedc]

Hey guys,

I did a gearing change (4.10 to 3.64) and put a limited slip unit in the front differential of my '03 X5 5 speed

Thought you might like to see some pics! They are on my facebook page!

www.facebook.com/bimmerpc


The combination of gearing change and LS unit is one of the best upgrades I've ever done on this truck!

Check it out!

[Ricky Bobby]

I remember your thread when the gearing change was done, would def like to swap in 4.4 Diffs someday, finding used good units is not cheap however.

[Green Dragon]

Originally Posted by sedc

Hey guys,

I did a gearing change (4.10 to 3.64) and put a limited slip unit in the front differential of my '03 X5 5 speed

Thought you might like to see some pics! They are on my facebook page!

www.facebook.com/bimmerpc


The combination of gearing change and LS unit is one of the best upgrades I've ever done on this truck!

Check it out!

Dude, I was just re-reading that thread last night. Question for you. If you made only the rear differential an LSD, would that cause the X5 to under-steer/push? I know having both differentials an LSD was discussed, and it lead to strong understeer, and that your solution was for the front only. What are your thoughts for this.

[sedc]

Originally Posted by Green Dragon

Dude, I was just re-reading that thread last night. Question for you. If you made only the rear differential an LSD, would that cause the X5 to under-steer/push? I know having both differentials an LSD was discussed, and it lead to strong understeer, and that your solution was for the front only. What are your thoughts for this.

Yes, having the rear LSD was not optimal when driving fast through corners. I am not sure what it would be like to have just the rear LS unit installed, I imagine much worse. I know having the front in place has saved me a few times this winter!

[Gregory891]

SEDC, congratulations. You've just discovered what is typically the most cost effective performance (acceleration or top end, depending on what you want & what you changed) item for a car.

Your signature doesn't mention what engine & transmission you have, so I don't know what would have a 4.10 from stock. From the ratio, it's likely a 3.0 L gasoline E53.

[Ricky Bobby]

yes he has a manual trans E53 3.0 with factory 4.10 gearing. If I could find an affordable set of 4.4 diffs (3.64) front and rear, I'd swap mine just to have the 3.64 gearing alone, would definitely drop the revs on the highway quite a bit and increase mpg.

[THE VEIN]

Originally Posted by Ricky Bobby

yes he has a manual trans E53 3.0 with factory 4.10 gearing. If I could find an affordable set of 4.4 diffs (3.64) front and rear, I'd swap mine just to have the 3.64 gearing alone, would definitely drop the revs on the highway quite a bit and increase mpg.

Would this work for a automatic 3.0?

[Gregory891]

In short, yes. This would work (and someone will find some exception) for essentially any brand or model. There are limits but I will not go into specifics of gearing, ideal final drive ratios or similar.

For THE VEIN, you will want to use either REALOEM.COM (BMW ETK parts software) with your car's VIN to determine the final drive ratio. Some BMW's have the same ratio whether manual or automatic, other's have specific ratios for the manual and automatic (of the same engine size).

If your 3.0 automatic also has a 4.10 ratio, then yes you would see a similar improvement in highway fuel economy to a specific detriment to acceleration. As an X5 has two differentials, you would need to change both and (naturally) both need to have the same ratio.

[Green Dragon]

Originally Posted by THE VEIN

Would this work for a automatic 3.0?

Short answer, yes. If you want to make the diffs LSD. If your wanting to change the ratios..... you may want to reconsider. Just guessing here. your automatic gear ratios as far as I know, are much better than the supplied gear ratios of the manual transmission. You could bump start the space shuttle with the manual transmission.

Manual Auto Pre LCI
1st 5.09:1 3.42:1
2nd 2.80:1 2.22:1
3rd 1.76:1 1.60:1
4th 1.25:1 1.00:1
5th 1.00:1 0.75:1

Final drive ratio 4.10:1 4.10:1
Notice the difference in first gears. And then the hole you fall into for second. The auto has a much better sequential flow in ratios. Also notice that you have a nice over-drive in the auto, where as with the manual, no dice. The 04-06 3.0 got a mild overdrive with a 6th gear (.84:1).

The GM 5L40-E Automatic was originally designed for a vehicle of about 4000 lbs, and 350nm of torque. The oem 4.10 final drive ratio is most likely a good match for the automatics. I would be afraid that the 3.64 ratios *might* put extra stress on the already problematic prone automatic.

Here's the ratios for the 4.4I auto pre LCI.
ZF 5 HP 24
Gear Ratios
1st 3.57:1
2nd 2.20:1
3rd 1.51:1
4th 1.00:1
5th 0.80:1

Final drive ratio 3.64:1
Notice how similar the auto ratios are between the 3.0 and 4.4. The V8's are about 500lbs heavier, and put out more torque, thus the need for a different gear box.

I'm still scratching my head as to why BMW choose the gear ratios for the 3.0 manual. Even with the 6th overdrive in my LCI, I will be swaping out my 4.10 diffs for the 3.64 diffs from a 4.4i. Better fuel mileage and and take some of the bite outta the granny gearing. There is also an option of going with 3.09 final drives out of diesel variants from Europe, but I think that would be too tall for the 3.0 and put it out of its optimal torque band.

Just guessing here.

[Sarek]

I believe the gearing in the manual transmission was to keep the tow rating. 1st gear is low for bmw standards but is not a granny gear in my opinion. Also having none or barely any overdrive helps prevent clutch problems with towing on the highway. Just a theory

I am very interested in how you modified the front diff? Or did you replace it with another unit.