Hey guys, got an '02 Blazer 4dr. Yesterday on the highway, it starting making this howling noise whenever I would let up on the throttle. If I gave even the slightest bit of gas, it went away. That was bad enough, but as I got into town and had to slow down she started shaking, wicked bad until I gave it gas again.
Made slowing down, very interesting.
Made it back to my place and immediately crawled under to see what's going on, and it's leaking pretty badly from the pumpkin.
Did some googling and most seem to think those symptoms are my pinion gear dying, I would like to play it safe and buy a rebuild kit from Advanced/ Autozone but I can't find what gearing is stock for my Blazer. I'm hoping someone here knows
Thank you for your time

 

Look in your glove box at your rpo sticker and match the 3 digit codes up with the corresponding one here
GU4=3.08 GU5=3.23 GU6=3.42 GT4=3.73 GT5=4.10 HC4=4.56
G80 - locking differential

 

I have no idea what an rpo sticker is, but I'll go look

 

There is a sticker in the glove box that has a list of 3 digit codes, each code identifies something about your truck. Find one of the codes that i listed and it will tell you your gear ratio.

RPO just means "regular production option" they are used to easily identify which options your truck has from the factory.

 

The safest way to be sure is to actually count the teeth of the pinion gear and the ring gear that way you're covered in case someone else changed the gears for whatever reason. Divide the number of ring gear teeth by the number on the pinion gear. Sounds like it's going to have to come apart to be cleaned anyway.

 

The ratio should also be stamped on the outer circumference of the ring gear. It will read something like 11:41, which would be a 3.73 ratio. Sometimes, it can be difficult to count the pinion teeth with the carrier installed, so reading the stampings may be easier.

 

I agree with Tom A. It should match the number stamped on the end of the pinion. I knew a little knucklehead who was just smart enough to be dangerous. He thought he could make whatever ratio he wanted by counting teeth and measuring bearings. It made a noise I'll never forget. No tears, it spun long enough to win. He turned out ok so I hear. He even found a bunch of people to talk about his truck with.

 

Got an update. No sticker in my glovebox, I see where it was but it was removed before the truck came to me.
I also tried wiggling the rear driveshaft trying to see if it had play, but it does not. I forget the details but I had read something about pre-load being bad causing similar symptoms to what I have. Thought it was worth a shot.

OK, so to see the stamp I need to remove the pinion, right? How do I do that and does it require any specialized tools?
Something just occurred to me, what if I get in there and I don't see anything broken? No excessive wear, broken teeth, etc?

 

To remove the pinion gear you have to remove the carrier out of the axle housing. Drain Fluid, Remove Cover, Remove Pinion lock bolt, Remove Pinion Shaft, Remove wheels, Push axle in and remove C Clip from each side and remove axles. Remove Bearing Caps on each side of the Carrier, Remove Carrier, Disconnect drive shaft from Diff. Remove pinion nut, Tap pinion gear shaft into diff. Now you can remove grease seal and bearings from inside to outside. The preload is controlled by a crush sleeve on the pinion shaft. At this point you can inspect the gears on both the ring and pinion for damage. The pinion gear has the following: Gear, Shims (Establishes Pinion Depth), Bearing, Crush Sleeve, Bearing, Oil Seal. The outer bearing and seal are installed from outside. At a min I would replace the crush sleeve and seal. The Crush sleeve provides the bearing preload and is established by torqueing the pinion nut to a free running torque of about 26 inch lbs with a beam style torque wrench. Be forewarned it is extremely hard to crush the sleeve. I had to hold the pinion flange with a pipe wrench with pipe extension going to the floor and very carefully using my impact wrench and if you over torque you need to get a new crush sleeve. YouTube has some good videos on Ring and Pinion installation. If you really want to do it right, new pinion bearings, New carrier bearings, New axle bearings and seals.

 

Damn. That sound like it might be beyond me. I'll watch the videos, maybe seeing it will make it click