3.90 Gear and Driveshaft Installed

Hi everybody and thanks for checking out my website,

Today’s project was to install a new 3.90 Ring and Pinion Gear along with installing a one piece driveshaft. The factory gear is a 3.46, and also came with a 2-piece driveshaft. I am hoping to gain a little more on the bottom end as far as speed goes with the new 3.90 gear, as well as putting in a lighter and stronger one piece driveshaft instead of running the horrible 2-piece one that the car comes with.

Special thanks to Kevin at Straightline Performance in Joliet Illinois for the install. Great work as always!


Motive Gear 3.90 Ring and Pinion
Differential 006Differential 005






Drive Shaft Shop 3.5″ Driveshaft 1000HP 1-Piece Aluminum Shaft with Direct-Fit Rear Flange

Differential 004 (2)



Drop the pumpkin, install the new driveshaft:



Remove the gears, install the new ones:

Use an excessive amount of heat on the side adjusters to remove them. Do not be afraid to use a torch. This is probably the hardest part of the job, and is the only way to remove the ring and pinion gear. Do not re-use the stock adjusters. Once they are removed, throw them away and install new side adjusters which can be purchased at GForce1320 Engineering.

Parts used from GForce1320 for the install (minus the gears). Click on the links under the pictures to visit the page where they can be purchased:

Gutted the differential and all new parts installed:



Unfortunately I have no pictures of the rear end re-installed. We ran out of time trying to get the car back together.


The new gears and drive shaft definitely made a difference. The car pulls great and feels faster. And having a lighter, stronger drive shaft makes the rear end virtually bullet proof!

Only real concern I do have is the gears are noisy. Which is a repeated complaint about Motive Gear 3.90 set up. Have yet to read or hear about a 3.90 gear install without any gear noise, so all is well.



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  1. How did you recalibrate your speedometer? I would be interested in doing a similar upgrade to my car, thanks!

    1. HP Tuners is what was used to re-calibrate the speedometer. I had my tuner do it for me. Good question, thank you.

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