I just wanted to say thanks for this thread. I attempted this this past weekend, front and rear 4.88s. I had never installed any gear sets before, the idea wasnt too complicated but i ran into quite a few issues that held up progress.
One thing i did is drianed both axles then filled them with diesel fuel. Then i drove it around the parking lot for 5 minutes to help clean the Red Line Heavy Shockproof oil i had it in. I wasnt worried about bearings since i was replacing them all.
When i opened the rear up i could move the carrier left to right 1/4" with it bolted in. I could rotate the pinion about 1/8 of a turn before engaing the ring gear. All of the bearing rollers and races were the texture of asphalt.
I couldnt get a good wear pattern at all on the rear axle, pinion was too deep but after some searching by myabe .006" on a similar gear/setup pattern i saw online. I tried every shim combination i had and even measured the pinion bearing height vs the new one (i machined the center from one) and found the checking bearing .008" taller and shimmed accordingly when i installed the final bearing. i ended up with .009" backlash which gave me a better pattern. I am using USA Standard gears which i understand are yukons that didnt make QC anyway so i figured it was the best i could do.
The front axle i tried for 2 hours to get the short stub axle out. I tried every combination of assembly, penetration oil, 10lb slide hammer, rubber mallet, 4lb hammer etc to get it removed. I even took it to a shop to get the axle out. They tried for an hour, then finally got it out with a slide hammer by wrapping a strap around the hammer slide and pulling as fast as they could.
After all that the front was easier than the rear. I got new locking tabs form GM PN 15588312 about $1.40 from the dealer, after reading the horror stories about them breaking, i put blue thread locked the threads of the adjusters, not sure if it will hold or make a difference but i dont think it could hurt it. I did have trouble crushing the crush sleeve on the front, the rear went fine, i used an impact, the front, i could not get it to crush. I had to crank my compressor up to 135psi and i have an air cat 1150 (supposedly 975ft lbs tightening at 120psi) to finally get it to crush. I removed the pinion to install the seal (i saw it suggested to get roating torque without seal first), and when i removed the pinion all of the rollers and cage fell out of it. It was a Koyo bearing, none of the race was dented or anything. I ordered a timken, and installed in place. I had a great wear pattern on the front, then i installed the new bearing and it went a few thousands deeper. I didnt worry about it too much, i was already 30+ hours into this job.
For the rear 4.88 gears i had to grind one tooth of the ring gear to get the cross pin back in.
I cleaned everything with brake clean, all new bearings housing etc. I replaced the axle tube bearings and seals. I filled the rear with oil, rotated it around 20 times then drained it since i had it apart 12+ times and im sure it got some dust and dirty in areas i couldnt clean out. I also rotated the front and rear pinion, and eaxl axle 50+ times in each direction once filled to ensure all bearings were oil before anything was put under load.
the front stayed clean and i had it apart maybe 5 times.
I bought the yukon tool though i dont think that you need it. I just kep loosening the case and making adjustments with my fingers until i had the correct backlash and preload. I sealed the case with the suggest 1184 (1194 has been replacedby 1184) and thats come good stuff. Says it's ready for gear oil in 20 minutes.
I filled both front and rear with just dino 80w90 oil for now. I will drain in 500 miles and put in some red line, a mixture of 75w90 and heavy shockproof i think.
There is a faint whine at cruise around 55mph when the gears warm up, Wehn cold i cant hear anything at all when it warms up its a faint whine but nothing bad at all, nothing like it was or anything that bothers me too much. I figured with a less than ideal gear pattern it would be a littel noisy, its actually pretty quiet, 4,88s are low gear anyway so i think they'd make a little more noise. I think with some run time and heavy shockproof the noise will go away. i only put maybe 1,000 miles a year on this (2001 suburban) and i tow my bobcat maybe 100 miles locally throughout the year. I think it will be ok.
With the rear gear i ended up leaving the pinion deep, any of the other adjustments put the pinion high on the tooth top land, right now its about 2/3 down towards the crown, and centered for the most part heel to toe, maybe a little towards the toe on both axles. There is a definitely line in the root on the rear but its not far down in it, i couldnt get it to go away without the pattern being on the top land of the gear so i just let it be.
I'll let you guys know if it blows up haha. I think it'll be ok, i'd rather the pinion be deep than shallow anyway.
thanks again for this awesome write up!
