While checking for u-joint condition on my '73, I noticed that the pinion yoke on the differential seemed a bit loose. So this past weekend I pulled the third member out and dissasembled it. The bearings and races on the pinion looked very nice, as well as the teeth of the ring and pinion. Using a new crush sleeve, I assembled the pinion together and torqued to about 175lbs (which is what my manual says). I checked preload and it was roughly 8 in. lbs. (which my manual also says is right. Then I assembled the ring gear assembly together, moved the left (drivers side) adjusting nut in untill the lash was gone, and tightened the right nut till it contacted the race, and turned it in three more notches (which the Chilton book suggests. Using my dial indicator, I checked backlash and got about .009 which apparently is also in spec. I did this a few times to make sure the bearings were fully seated.

I reassembled it and took it for a drive. This third member never made any serious noise before, but now it wirrrs with increasing speed up to about 50mph, and then a bassy rumble takes over. If I let the clutch out, the rumble continues down to about 25 mph. Obviously, I've done something wrong!!! Can anybody tell me what??? Polkat

 

You said you were checking a u-joint condition? Did you solve that yet? That noise you described sounds like when my u-joints went bad.

 

Yea, I did solve that. All the u-joints were good and tight, but I did notice that the very fron joint had it's grease fitting (zerkel fitting?) missing. I put a new joint in but the noise persists. Frankly, even though I used a new crush coller and torqued to 175 lbs, I think I have too much preload on the pinion bearings. The best way to discribe the sound is that it's like a little miniature jet engine back there that revs up in time with the speed of the axle when going forward. I don't hear it slowing down. I hear it speeding up even if I push the clutch in for a few seconds and let the engine die down. At about 45 or 50, the sound changes to a very low rumble (kind of like the sound you hear in a strong earthquake. This is ther regardless of speed above 45 or so. It is not a wheelbearing! I've checked all four corners and the wheelbearings are excellent.
Any ideas? Polkat

 

[updated:LAST EDITED ON 27-Sep-02 AT 07:03 PM (EST)]I would have to say, you have either a bad driver side carrier bearing or your pinion bearings are shot. Also, you probably tightened the backlash up quite a bit from where it used to be, that will also make a noise, when a gear is used to running with alot of backlash and you tighten it back up to spec, most of the time you will have noise.

 

Thanks for the advice Diffmaster...makes sense. But does that leave me with anything to worry about as far as gear mesh is concerned. I am assuming that the noise is caused by the wear on the old contact point trying to get along at the new contact point. Should I expect accellerated wear now, or will the new contact point eventually wear in? Also, when I had the pinion apart, I took a serious look at the bearings and races and saw no heat checking or unusual wear, and at present it takes about 8 inch lbs to turn the pinion. So I think I might be okay with the pinion. Oh, by the way, yesterday I went and turned the back half of the drive shaft 180 degrees and a great deal of the noise (the deep rumbling sound-although there wasn't much viabration)went away!!! The spider gears are pretty much shot, and I'm thinking of going to a Right Lock unit. Any opinions? Thanks again, Polkat.

 

if your going to pull the diff again. might as well splurge for a full detroit. IF the cost is bothersome to you on the detroit. you can get used ones from ebay for less than $300 shipped to your door with little usage on them.

I am currently using a used detroit from ebay. I have blown up a complete 3rd member but the detroit lived. When you set the back lash to spec. did you check the gear mesh as well with gear compound?

 

One other thing I forgot to mention, is did you get the pinion depth shim back on, it's the 5 hole stamped steel shim, that goes between the pinion support and the 3rd member housing? No, on the noise question, the gear will not wear in, it was used to running in one spot, and now it has been moved, the only way to quiet it up again is to loosen it back up. You can tighten or loosen them when they are new, with low miles, but not once they have been ran a long time. It's probably time for a new gearset. I also recommend the Detroit, it is forever. I have seen to many lock rights with problems to recommend them, sorry. Spider gears will not make noise going straight down the road, unless you have 2 different size rear tires. Let me know what you decide to do.

 

Detroits are great, but a little cost prohibative. I have run several lock-rights in a few different trucks and never had a single complaint. Best part is not having to redo the R&P setup with one. Unless you are planning on putting over 500hp into a locker, than the lock right should hold up great. And you can get a new lock-right for the cost of a used detroit.

 

I am not going to dissagree. but in my application where I am out doing some pretty hard core wheeling. lock rites suck. When I get on it I do not want it to break. thats why I chose the full detroit.

And your only resetting backlash it is not that hard if your good with your hands.

 

Thanks for all the info guys!!! In the end I think my pinion preload is too high, so I'll pull it again, check the bearings, get a new crush sleeve, and this time instead of going to the suggested torque, I'll just torque it up to the factory preload. Apparently you don't HAVE to have 175 lbs of torque on the pinion nut, but rather whatever torque it takes to get the 8 inch lbs. of preload. I have no problem with R & P backlash, and will double check the side bearings.

As for the posi....heh, heh, everyone gets made if you call it this, but lets face it, they are all positive traction units regardless of the name...I don't know. There are a lot of them out there to choose from. I guess it depends on what you're going to do with it. I race now and then, and everyone knows an empty truck doesn't have a lot of weight on the rear, so an open diff is a disadvantage. Mostly I haul loads over dirt roads and I often hear that right rear spinning by itself. The lockright seems like a fair compromise for performance and price.

I'll post what I find when I open it back up. Thanks again, Polkat.