Replace ring and pinion gear , or just bearings?

My dad's 99 XLT (99,000 miles) has been diagnosed with needing a new rear end. He has the standard issue of bad grinding/whining while accelerating, but it goes away when you get off the accelerator. Sounds like pinion bearings to me, but the mechanic he took it to said he can put a used rear end in there for 1200 dollars.

Now I'm not exactly sure what the mechanic means by "rear end". My dad is going to call him on Monday to find out, but after some research, it seems like the better idea is to rebuild the diff. I want to do this for my dad since has done so much for me, and I am a decent shadetree mechanic. But I am unsure how much needs to be replaced. Is the ring and pinion gear normally a replacement item? I think I can probably get away with just bearings and seals. After checking online, I see several different rebuild kits or bearing kits for this truck. It's also a LSD, will that make a difference? I know the best plan is to pull the cover and look, but he lives in Wilmington (six hours away) and I will have to do the work in one weekend, so I may not be able to get parts right away down there. I'm trying to get everything together for the work.

Also, does anyone have any recommendations on an on-line parts store for the rebuild items?

TIA,
Chris

I just bought an 8.8 rebuild kit from www.completeoffroad.com, got what I feel was a pretty good price.

If the rear end has been making noise for a while now, I'd think your gears are probably shot as well.

You should be able to rebuild the whole rear end for ~$300 worth of parts, including new gears. Assuming you do your own set up work.

I would be very careful of rebuilding your rear end. You have to start off with setting your pinion depth then setting up the backlash between the ring and pinion by changing spacer thickness' on either side of the carrier. I have not ever done this myself before but have watched a couple guys do it before. You will need to know how to blue the gears adn know what you are looking at to set up the backlash. It is quite a job especially if you are doing it under the truck. I would say put a used rear end in it or pay to have it rebuilt. I would think that you can get it rebuilt for the same amount as putting a used one in it, but that is my opinion.

Thanks for the replies. I know it takes a lot of patience and know-how to adjust the backlash and get a good mesh pattern, and I'm willing to do it. Will it matter that it's a LSD?

Also I'm thinking I will need a decent dial caliper as well. Any other specialty tools you can think of?

BTW I saw Creager's write-up on swapping gears and installing a Trutrac. It looks difficult but within my ability. Excellent write-up too!

Also how difficult is it to pull the pumpkin? I might just buy a used one, rebuild it up here, and drive it down for the install.

Excellent. Your reply is pretty much on par with what I am thinking I will need. I will check out the website you mentioned. Too bad about the pumpkin; that sure would have made things easier.

If you have an LSD, which is a limited slip differential, a junk yard replacement axle could cost more than if it was open.

Another thing you could do would be take the rear end and have a shop set up the gears. I called my local Ford dealership, they will charge 3 hours for labor for the front and rear differential, assuming I brought them in to the shop. That way the set up would be guaranteed. I they should only charge an hour or hour and a half for the rear by itself. Either way, your still below half the cost of a junk yard rear end.

If I were to purchase an axle from a boneyard, which years am I looking for? Is it strictly 95-01?

Actually, you will need an axle from 97.5 and up. It has to have the speed sensor on the rear end so the speedo will work. Earlier models had it in the T case.

My old 92 had the sensor in the rear pumpking. Not in the transfer case.

Oops, Sorry, I thought you meant the abs sensor.

I rebuilt the rear, with posi, in my 96 last summer. Took two days cause I had no help. I had a whine in mine three months after the Ford dealership replaced the pinion seal, turns out they used an air impact wrench to put it back together, WRONG!!!!!! Anyway rear started screaming. When you take the rear apart you will find that the gears are probably good, it is the pinion bearing that makes the noise. If the gearsa are good the rebuild is relatively simple. The thing you have to remember is DO NOT LOSE ANY OF THE EXISTING SHIMS! As you take ring assembly out there will be shims by the bearings on both sides. Take each set out and put a plastic tie around each set, mark left and right. I suggest you get a good 1" micrometer and measure the thickness of each set and record on paper, again left and right. The pinion is easier, take off the yoke and pull the pinion assembly out the back of the housing. The shims will be between the gear and the bearing. Push off the bearing, collect and plastic tie the shims, and record on paper. Buy the bearing rebuild kit that Timken's sells. Grab the pinion gear and place in freezer for 1 hour, at same time place new bearing in 300deg. oven for same time length, Remove pinion and quickly place new shims on (same thickness as before), and pinion bearing (from oven), it should be very easy to set the bearing. You may have to bump with a hydraulic press though. Keep pressure on bearing for approx. 30 seconds to prevent creep. Replace pinion bearing race and pinion seal in pumkin. Tap out with brass rod and hammer, reverse to install. Put pinion assembly back in pumkin with new crush spacer. Now here comes the hard part, having a second set of hands will make the job easier. You need to drive the yoke back on using the nut, the hard part is you are trying to establish a torque value that the pinion will spin at. The spin torque value of the pinion is in inch pounds while the amount of torque your putting on the yoke nut to move the yoke in is ft pounds. Using a good torque wrench thighten the yoke in 10lb increments, checking the torque value to spin the pinion with the inch pound torque wrench. Remember you're working with just the pinion in the rear no ring gear assembly yet. Get the pinion torque to Ford spec and you can now address the ring assembly. Pull and replace the axel bearings. replace each ring assembly bearing adding the same thickness as you removed. Torque caps down and you will find you have the same backlash and tooth contact. Botton her up and you're all set. Like I said I did mine by myself in my driveway, including removing the rear from the car in two days. Been driving for nine months (approx. 32K) with no noise at all. Hope this helps.

Guess I'll throw my 2 cents in and say that I had the same whining/grinding sounds as you, I had it in the garage today and they replaced the axle seals on both sides refilled it with new synthetic gear oil I drove it 100 plus miles from the garage back home. I have no more gear or rear end whine at all. I asked the mechanic if the oil seamed like it was low and he said "no it was fine". Perhaps I missed something in your post but it cost me about $4 or $5 for two seals and $45 labor to replace both sides.

Wow, Where did you find someone willing to do the labor for $45?