83/4 Ring and Pinion swap questions.

[rusty dodge]

I wanted to try and do this myself, and have found lots of info about how to do it. But I was wondering about the pinion bearing. This is in a 742 case, clutch type S.G.. and I wanted to know how to get the bearing onto the pinion. I'm assuming the pinion bearing should be replaced and not reused off of the old pinion. Do I just bring it to Like NAPA and have them press it on I guess? What about the pinion outer race inside the housing? Does that need to be pressed out, or can it be tapped out by hammer?

If I also want to replace the clutches, will those 2 bearings need to come off to get the sure grip apart?

As a side question, how any hours would it take for a pro diff. shop take to switch a ring and pinion? I'm getting quotes of around $250 labor only to do this. Seems fair if it takes 3-4hrs to do. I don't think it would take that long for someone with experience though.

Thanks
Terry

[Plum6Pak]

Hey Terry, the diff isn't that bad to do but there are some important things you need to know before diving in. If you install your new bearing onto the pinion with the wrong shims behind it, you will need to remove it to get the right gear pattern and that's where the trouble starts, if you don't have the right equipment it will be a real job. If you can get someone from a place that does these on a regular basis to at least check it and tell you what thickness of shim you need, that will take a lot of the work out of it for you. A good qualified shop should have the test bearing setup that they install on the pinion, check the gear pattern then install the correct shims and bearing once they have that all figured out. One way is to get a pinion bearing and have the inner cone honed out enough that you can just slide it on by hand, you can set up your pattern and make sure everything will work, then remove the test bearing and install the permenant stuff. A bearing heater is the way to go for installing the pinion bearing, you don't want to use a torch but you could get it hot in the oven if you don't have a bearing heater. It will need to be about 400 degrees, you make sure you have the correct shims on the pinion and it doesn't even hurt to have the pinion in the fridge for a while. Once you are ready, you can actually drop the bearing onto the shaft and once it cools, it's not going anywhere. Just some tips, there are probably a bunch of others as well but that's as much as I can tell you.

[rusty dodge]

Thanks Plum6pac, I see why this gets difficult. When I took it apart I saw some shims that were on the end of the pinion, on the outer side of the bearing, and 1st thought those were the shims to adjust the gear pattern. But those shims must be for the yoke to tighten up against, or for something else. The ones that actually adjust the pattern are under the bearing, which I havn't taken off.

So I would need to get 2 pinion bearings, so I have 1 to open the ID to be able to check that bearing thickness, Then put it together with the other bearing and hope I got it right.

[Plum6Pak]

I don't remember where but there is a website that will explain setting the gear pattern up and it shows a picture of the correct pattern. Try doing a search on setting up the Mopar 8-3/4 rear end and you should get something. The side bearings are the pinion to ring clearance which is about .010 and can be set with a dial indicator, the shims behind the pinion bearing are to set the depth. If you are just installing a new bearing and re using the gears you can usually plan on using the same amount of shims but if you are going with new gears you better go with the test bearing. The shims under the yoke are for your bearing pre load, on the 742 housing you install or subtract shims to get about 20 inch pounds to roll the pinion. On a 489 housing it's a crush sleeve and you tighten the yoke nut that crushes a sleeve until you get the correct tension but once the sleeve is crushed it shouldn't be re used so the 742 is more forgiving. When you are tightening the yoke for your pre load test, check how much tension is on the bearing as you get close just in case you don't have enough shims to keep the bearing from getting damaged. Best to start on the too many shims than not enough just for that reason. You can knock the old races out with a flat punch, just go through from the back side and tap on each side so it doesn't get c0cked in the bore. You can take that old race and grind the edge a little and use it to tap the new race in, you will need to put a large washer or something over it to be able to pound the race in from the center so it doesn't get c0cked going in. Have fun removing the pinion race if you don't have the right press, I usually use my air cut off wheel and carefully cut the race but you need to be very careful not to cut into the pinion shaft. When it gets thin it will start to turn orange as the thinner metal will heat up quickly and you know it's close enough. As far as the sure grip, I haven't rebuilt the clutch type before, only torn apart and cleaned up the cone type. Maybe someone can chime in and help you with that one. Best I can do, I don't have a book or any specs other than what I can remember out of the old rusty memory. Personally, if you have doubts about doing this correctly or if you just don't have the right tools, I'd have a reputable shop do it for you. Nothing you can't do yourself but it can turn into a real butt ache if you do it wrong. Maybe you could go to the library and get a book that will help you. Good luck, let us know how it goes.

[moper]

Rusty, I do a few a year of various 8 3/4  chucks. I have brand new bearings for all ,that I used a stone to enlarge until they can be removed by hand(with a little tapping). These are my "checking bearings". They have to be brand new to work right tho. It usually takes at least 3 setups before it's done the last time, and for that time, I use a press and the unmodified bearing. More important really, is a turning torque type wrench. It's not a torque wrench, it measures required rotating force. Get that right, and the pattern right, and the backlash should be perfect. I also wont do partial repairs. If the bearings were bad. the ring and pinion have worn in a bad way, and may be noisey even with new bearings. So I replace the R&P, plus all the bearings every time. That $250 tag for labor was right on the money IMO.

[rusty dodge]

Thanks guys.

[Plum6Pak]