Rear end broke what gears now

[fun4me]

The pinion broke two teeth off & the ring gear is all chewed up. No damage to the axles or the housing. I'm gonna install a truetrac & lower gears. The big question is how low should I go? I'm liking the 4.11 but I think 3.90 would be a better all around gear. Its a vortec headed 383 with the LT1 hot cam. Wheels are stock 15's

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[DRAGGIN95]

What tran's do you have?

 

[fun4me]

4L60E

 

[DRAGGIN95]

Yeah 4.10's would be fun with that trans, but I have had 2 truck's with 4.10's and a 4L80e and they are to wound up on the interstate for me, but the 4l60E has more overdrive than the 80 does.

 

[fun4me]

The 4L60E has a .70 overdrive, what is the 4L80E?
What RPM's were you running at 70 mph?
Also what was the height of the tires you were running?

 

[DRAGGIN95]

With 29.8 tall tires 2800rpm at 70mph in OD.

 

[fun4me]

What overdrive is in a 80? I did the math with a 29.8" tire & a .70 overdrive & I came up with 2,265 rpm's at 70 mph
(mph)x(trans ratio)X(gear ratio)x(336)/(tire diameter)=rpm
(mph)x(.70)x(4.10)x(336)/(35)=rpm
(70)x(.70)x(4.10)x(336)/(29.8)=2'265.18120805

 

[DRAGGIN95]

I rechecked the tire size and it was 29.3 not .8 and the 4L80E has a .75 overdrive.

 

[fun4me]

I did the math for the a 29.3 tire with a .75 final drive (25% overdrive) & I came up with 2,468 rpm at 70 mph

 

[fun4me]

If I round the numbers then it's only about 100 rpm difference between the 3.90's & the 4.10's.

4.10=2,410 rpm's @ 70 mph.

3.90=2,293 rpm's @ 70 mph.

Big whopping 117 rpm's difference.

I'm ordering the 4.10's