Rearend Rebuild

Sean91LX · Dec 31, 2015

Hello all,
Yesterday I had installed on my '91 LX automatic some 4.10 gears, axles, and a new differential. Now, I am currently in the break in stage, but to me it seems as if the gears are the same thing as what I had on the car. (Which was completely stock). So it almost seems like they got my gears mixed up and installed the wrong ones. If so, how would I be able to tell? And if they are correct, would I feel a major difference right away? Because it seems like the same old long shifts from the old gear sets.
Thanks,
Sean

RangerJoe · Dec 31, 2015

You said you are in the break in stage, meaning you haven't got on it yet? Wait until you can thrash on it and then you should see a difference. You can Google search it, but you can jack up the car and rotate the rear tires, while counting the drive shaft rotations. You can figure out your gear rato from there.

Joe

84Ttop · Dec 31, 2015

Jack up the car, Use jack stands..
Place the car in neutral
Center the valve stem at the peak of the rotation on one wheel.
Make a chalk mark on your drive shaft
Spin the wheel 1 complete revolution while counting the revolutions of the drive shaft
If you have 4.10 gears the drive shaft will spin 4.1 times with one wheel rotation.
If you have 3.73 gears the drive shaft will spin 3.73 times with one wheel rotation.
Etc, Etc, Etc.

Sean91LX · Dec 31, 2015

RangerJoe said:
You said you are in the break in stage, meaning you haven't got on it yet? Wait until you can thrash on it and then you should see a difference. You can Google search it, but you can jack up the car and rotate the rear tires, while counting the drive shaft rotations. You can figure out your gear rato from there.

Joe

Yes I am still breaking it in. I just figured I would feel a difference right away. But I will wait till I can get on it to see. And I will try what you said and count rotations. I might even change the oil sooner than later to check that also.

mikestang63 · Dec 31, 2015

gears are the best performance bang for the buck. You will notice a big difference. A few things to consider

did you change the speedo gear in the trans to compensate for the different gear ratio? If not your speedo will be about 20MPH off at highway speed
Know that your trans will now shift sooner in lower gears due the lower gear ratio. You may need to install a shift kit, valve body or at a minumum adjust the TV cable

Sean91LX · Dec 31, 2015

mikestang63 said:
gears are the best performance bang for the buck. You will notice a big difference. A few things to consider

did you change the speedo gear in the trans to compensate for the different gear ratio? If not your speedo will be about 20MPH off at highway speed

Know that your trans will now shift sooner in lower gears due the lower gear ratio. You may need to install a shift kit, valve body or at a minumum adjust the TV cable

I haven't really noticed a change in MPH

mikestang63 said:
gears are the best performance bang for the buck. You will notice a big difference. A few things to consider

did you change the speedo gear in the trans to compensate for the different gear ratio? If not your speedo will be about 20MPH off at highway speed

Know that your trans will now shift sooner in lower gears due the lower gear ratio. You may need to install a shift kit, valve body or at a minumum adjust the TV cable

Yes I figured there would be a change in MPH but I haven't really noticed it. Even though I can only go 50 right now. But yes I have a shift kit in the tranny. I just don't know how to adjust the TV cable unfortunately

CarMichael Angelo · Dec 31, 2015

Sean91LX said:
I haven't really noticed a change in MPH

Yes I figured there would be a change in MPH but I haven't really noticed it. Even though I can only go 50 right now. But yes I have a shift kit in the tranny. I just don't know how to adjust the TV cable unfortunately

If you changed from a 2.73, to a 4.10 it would be night and day across the board from the moment you rolled away. First gear would come immediately, the car would be significantly more spirited. Unless you are babying the thing, the tires will break loose w/ almost no provocation in 1/2.. and the engine will wind it's balls off at 70 mph in 4th.

You could do as 84 T top as recommended to be sure exactly what they put in there but there is no way in hell you wouldn't notice that significant of a gear change even going to church.

Rearend Rebuild

Sean91LX

Member

RangerJoe

I leave the horn on while driving

84Ttop

They make new pistons every day, so why worry?

Sean91LX

Member

mikestang63

Sean91LX

Member

CarMichael Angelo

my rearend will smell so minty fresh,

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Rearend Rebuild

Sean91LX

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I leave the horn on while driving

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They make new pistons every day, so why worry?

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mikestang63

Sean91LX

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my rearend will smell so minty fresh,

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