The Stovebolt Site Forums The Shop Area Driveline Identifying the rear pinion gear size

Hi guys....I have a 64 1/2 ton k10 4x4 pickup. It was a former tow truck. There is a lot of noise coming out of the rear differential and the driveshaft is very sloppy.

I believe I need to replace the pinion gear. I don't know how to identify the pinion gear size. Does anyone know how I go about identifying the size and where I would find a replacement?

I welcome any thoughts or direction on what I should do. I'm not familiar with doing this kind of work. Thanks john.

Ring and pinion gears are replaced as a matched set- - - -not individually. Chances are you've only got a failed pinion bearing unless it's been run for a long enough time to get gear damage. It's going to require a full teardown and cleanup, as there are two bearings on the pinion gear, and replacement of the inner one can't be done from the outside.

I'd strongly suggest finding someone who is very femiliar with rear end repair to do the work- - - -it's a complex operation with a lot of opportunities to make expensive mistakes.
Jerry

I brought my truck to a trusted mechanic and he was horrified at the way the truck drove. It turns out that my two u joints were ready to fail...a couple of the pieces were rusted completely off. The pinion nut needed about a 1/2 turn of the wrench. He couldn't believe how long I've been driving the truck this way....over three years. He had never seen a drive line so loose.

I got my truck back with two new ujoints and a tightened pinion nut....and it's like night and day the way the truck drives. I'm amazed. It's quieter, drives smoother, has improved acceleration and it feels like I'm getting the most out of my 283.

I would drain and refill the rear diff to help flush the filings out if you have been running a loose pinion nut, and while you are there look over the gears then you will know what you ratio is and what kind of shape they are in. It is never good to have a diferential come apart while on the road!

Good idea pope. How do you determine the gear ratio? by counting the ridges on the gears? Regarding wear on the gear...what would you suggest I use as a reference point to determine any damage or wear? Thanks John

Look for rounding of the tooth edges along with chips, brinling (looks like ripples) and contact pattern. Basically if it looks bad it probably is lol. If you google differential contact pattern you should be able to find pictures of what you are looking for for wear. The teeth should have sharp clean edges and not be rounded off. To get the ratio take the ring gear tooth count (EX 41) and divide by the pinion tooth count (EX 11), so 41/11 = 3.727272 or a 3.73 ratio

A pinion nut that's loose is an indication of bearing wear. Tightening the nut is only a temporary fix- - - -it will get loose again in a very short time. As the pinion bearings continue to wear, they will get noisy and eventually fail altogether. Be on the lookout for a hum or whine that changes pitch as you go from pull to float to coast. If you haven't run for very long with loose bearings, it might be possible to swap them out before you get major damage to the gears. It's sort of a crapshoot, though!
Jerry