Final drive swap

JSATX

JSATX

Goblin Guru
I know many have referenced the different final drive ratios available and talked about using a different final drive from HHR, but has anyone actually done this swap? I have the tallest (3.63 XFE package) final drive they made in any of these cars and it just isn't suited well to my goblin. I sure dont care about 80mph highway gas mileage.

Interested in what it would actually take to swap that out or if thats not possible and I just need to get a whole trans out of an HHR.
 
George

George

Goblin Guru
If you get the ratio too low then you will no longer need 1st gear. As a benefit the other gear ratios get close together but top end is reduced.
Brad
 
JSATX

JSATX

Goblin Guru
Not too worried about that, my first gear goes almost to 40mph as is, and my top end is way higher than this car can go.
 
JSATX

JSATX

Goblin Guru
George said:
How many mph do you want out of 1st gear.
To get the best 0 to 60
Brad
Click to expand...
That’s a good point. Theoretically hitting it before second redlines is ideal, my new build will rev to 8k so i think it’ll work with pretty much any of the final drives.
 
George

George

Goblin Guru
JSATX said:
That’s a good point. Theoretically hitting it before second redlines is ideal, my new build will rev to 8k so i think it’ll work with pretty much any of the final drives.
Click to expand...
With the 4.05 and a 8000rpm limit I am very happy with the gear ratios but my power level is only 270hp at the wheel. If it had more power a diff ratio of 3.8 might work better.
Brad
 
George

George

Goblin Guru
If the ratio is too low and a lot of power sometimes all you wind up doing is spinning the wheels. my engine also turns 8000rpm and I only need 1st and second gears for 0 to 60. if you are getting 40mph in 1st now with a 6000rpm red line and the turn it 8000rpm you will be doing about 53mph in 1st. With a little bigger tire and enough power you may not have to shift to do 0 to 60?

Brad
 
George

George

Goblin Guru
The other way would be to use a lower ratio (4.45) and launch in 2nd that would make the 2-3 shift a closer ratio change. So many ways to go.

Brad
 
SliderR1

SliderR1

Well-Known Member
I agree with Brad - once you get the power up, the ratio you have should be close. I've got the MU3 F35 with 4.05 final and first feels very short. My LSJ is very lightly modified and I'm running tires with almost the same overall diameter as stock.
 
Lonny

Lonny

Administrator
Staff member
I had always thought as you remove weight and add power you move to a taller final drive. Like from a 4.05 to a 3.83.

If you are at a prepped drag strip and you dump the clutch at 4500 rpm and the car launches without lugging you need to go to a taller final drive.

If you car does lug you need to build a bigger motor. ;)

My Stock SS/SC Goblin launches without lugging on a prepped track. (205 h.p.) My biggest problem is first gear is instantly at red line. I feel I need a taller final drive as it is. If I were to up the power I would most definitely need to change my ring and pinion to something taller. It has a 4.05 right now.
 
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