Help.. gearing stupidity

[DnvrJay71]

Ok so I've never changed out gearing and want to know A.how much trouble I'm getting myself into...... or B: which ratio works well for you.
Bought a manual 350, 71 K5 earlier this year and it currently has 3.08. It feels dog slow off the line but has great power once rpm's are up. I'm currently running 33's w 4 in. suspention lift. I really don't want to get totally into rock crawling since the truck a fun family 4wheeling\camping type machine. So if I want to possibly run 35's in the future, but still have some type of highway capability; would you all recommend 4.11 or 4.56?

[AlaskaMatt]

I have 33's with 3.73's and turn ~2800 rpm at 65. I would think 4.56 would eliminate reasonable highway driving even with 35's.

[bouncytruck]

I've had three blazers, each with different gears. My first had a 4" lift with 35's and 3.73's. It was sluggish off the line. My second had 6" lift with 35's and 4.10s. It seemed better suited to the tires. My current truck has the 3.07s and tires approx 31.5" tall. It is by far the most drivable.

[truckster]

Originally Posted by AlaskaMatt

I have 33's with 3.73's and turn ~2800 rpm at 65. I would think 4.56 would eliminate reasonable highway driving even with 35's.

I would agree. I have the same setup, 33s and 3.73 ratio, and I think it's a good compromise between highway driveability and some mild off-roading.

[Torrey72]

As much as I like to drive the streets. 4.10 is as low as I would go for a truck with 33/35 and a trany with a 1:1 3rd. If it will never see the free way or Hwy 4.88 would be cool to have. If you have the money you can put a 4 speed over drive in it and go low with no prob.

[DnvrJay71]

Ok so next part of the question is, how hard is it to replace the gearing? special tools?

[SeventyOne]

Special tooling yes and a lot of patience getting the bearing preload and backlash correct.

[DANTES JIMMY]

Get a book or somebody who has done it
lots of patience in and out multiple times and adjusting backlash and tooth depth as far as tools goes i dont remember much special. .bearing pressed on to the pinion gear if memory serves me

[SeventyOne]

Press, setup bearings (make them yourself), dial indicator, accurate 1/2" torque wrench, seal driver, locktite...That should cover 95% of it.

Maybe a pinion depth tool and a case spreader...

[badpeanut]

It may be cheaper for you to find a different set of axles and swap them in. If you are looking for another 12-bolt rear axle you are limited to '69-'72 4x4 to get the correct spring perches and shock mounts. For the front axle you can use any '71-'76 GM truck Dana 44; a '77-'91 corporate 10 bolt front axle could also be used with a driveshaft length modification.