Rear Axle Rebuild Question

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration
Model T Ford Forum: Forum 2013: Rear Axle Rebuild Question
Top of pagePrevious messageNext messageBottom of page Link to this message  By Randy Clemens - NW Phoenix AZ on Tuesday, October 08, 2013 - 12:36 am:

I am currently overhauling the rear axle and have a question about a wear / clearance measurement. I read through the manual but It's still not clear to me.

I understand that max wear in the ring gear housing at the side gear bearing is .010. Is this considered wear or clearance?

My side gear measures great at 1.807 and the housing measures out 1.815 or .003 oversized. I therefore have .008 clearance.

Would the maximum oversized measurement on the housing be 1.822 equaling .010 wear?

or:

Would the maximum oversized measurement on the housing be 1.817 equaling .010 clearance based on the gear size given above of 1.807?

I hope I explained this in a way that makes since as it is hard to explain.

Thanks in advance

Randy


Top of pagePrevious messageNext messageBottom of page Link to this message  By Philip Berg on Tuesday, October 08, 2013 - 02:38 am:

This can be somewhat confusing to non-machinist types.

Ex:

1.0 diameter part with a tolerance of +/- .003 can range from .997 to 1.003

Tolerance can be in the plus and minus direction or in the minus direction only, or in the plus direction only.

1.0" +/- .003

1.0" +.003 -.000

1.0" +.000 -.003

If your housing bore nominal size is 1.812" then a max wear of .010" would give you a bore size of 1.822". Bores normally don't wear smaller.

I would say the .010" would be considered wear and not clearance.

Clearance between the two parts would be their respective nominal dimensions adding tolerance (+/-) and then subtracting opposites (large to small, small to large) of each part to get clearance.

I won't get into geometric tolerancing that's another ball of wax.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Randy Clemens - NW Phoenix AZ on Tuesday, October 08, 2013 - 10:48 pm:

Thanks Philip

It doesn't seem correct that the allowable clearance would be a total of .015


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Menzies on Wednesday, November 27, 2013 - 10:21 pm:

I would like to understand your concern a little better. Firstly there are no adjustments on a "T" differential, new parts must be replaced. The housings that contains the inner roller bearings are sleeved with a split sleeve so if there was a variable in the casting the sleeve would compensate. End play is taken up with a bronze washer sandwiched between two steel washers that's all no further adjustments. Ring and pinion sets were made by several gear makers and tolerances as much as .040 were common, however today we try for .004 - .006 it is difficult to make them any less because there are no shims to take out. With so many different gear makers in the day tolerances wern't that close. The gears were cut very accurately but when they were hardened they would warp some the same as gears today. Modern differentials can be adjusted for a specified clearance not so with a"T" differential. If the assembly is binding in any way a paper shim is available to be placed under the ring gear for additional clearance. The Ford differentials are very simple with no adjustments. If sleeves and bearings and the bronze and steel washers are installed there is no more to do. I pulled a 15 diff apart that was so bad the crown gear was rubbing on the housing. I replaced the bearings and sleeves, bronze and steel washers and it was restored back to within tolerances, I had to put one .003 paper shim under the crown gear. The differentials were fairly forgiving because they ran with grease. Extensive measuring serves no purpose because replacing with new parts will return it to standard. The outer sleeves are installed, bearing is installed cap with felt and washer then hub felt and the wheel is installed there is no more to it than that. Other issues like bent housings can cause serious problems but they are uncommon. If you have a straight housing only new parts have to be installed and you should be good to go. You can frequently find good used parts for the assembly. Don't be intimidated.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Menzies on Wednesday, November 27, 2013 - 10:23 pm:

I would like to understand your concern a little better. Firstly there are no adjustments on a "T" differential, new parts must be replaced. The housings that contains the inner roller bearings are sleeved with a split sleeve so if there was a variable in the casting the sleeve would compinsate. End play is taken up with a bronze washer sandwiched between two steel washers that's all no further adjustments. Ring an pinion sets were made by several gear makers and tolerances as much as .040 were common, however today we try for .004 - .006 it is difficult to make them any less because there are no shims to take out. With so many different gear makers in the day tolerances wern't that close. The gears were cut very accurately but when they were hardened they would warp some the same as gears today. Modern differentials can be adjusted for a specified clearance not so with a"T" differential. If the assembly is binding in any way a paper shim is available to be placed under the ring gear for additional clearance. The Ford differentials are very simple with no adjustments. If sleeves and bearings and the bronze and steel washers are installed there is no more to do. I pulled a 15 diff apart that was so bad the crown gear was rubbing on the housing. I replaced the bearings and sleeves, bronze and steel washers and it was restored back to within tolerances, I had to put one .003 paper shim under the crown gear. The differentials were fairly forgiving because they ran with grease. Extensive measuring serves no purpose because replacing with new parts will return it to standard. The outer sleeves are installed, bearing is installed cap with felt and washer then hub felt and the wheel is installed there is no more to it than that. Other issues like bent housings can cause serious problems but they are uncommon. If you have a straight housing only new parts have to be installed and you should be good to go. You can frequently find good used parts for the assembly. Don't be intimidated.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Menzies on Wednesday, November 27, 2013 - 10:24 pm:

Sorry for the double tap


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Gould on Thursday, November 28, 2013 - 08:40 am:

Whether you call it clearance or wear, if you have 8 thou difference, you are in good shape. Honestly, you don't find that close a fit often. If you measure the bearing surface on axle gears you will find a lot of variation, both from wear and manufacturing tolerances. In my experience, 8 thou is darn good. BTW, don't take everything you read as gospel. EG different versions of the Ruckstell restoration book call for either 4 to 6 thou or up to 10 thou ring and pinion clearance. The quietest rear end I rebuilt had 15 - 17 thou clearance. Ford's clearances were much greater, some say 25 thou. Have you ever wondered why we must now use shims behind the ring gears to bring them to modern clearances?
Another BTW, if you were to measure clearances on original Perfecto innards, you'd have a real shock. EG pinion to pin clearances range from 10 to 20 thou clearance. On Ruckstell rebuilds, we now strive for 5 thou.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Randy Clemens - NW Phoenix AZ on Thursday, November 28, 2013 - 09:43 am:

Thanks everybody for your help with this. I got the rear axle together and it went very well. All that's left is to paint it and put it back in the car.

I installed the fun projects pinion kit and the needle bearing at the top of the torque tube but I have gotten some comments about using the needle bearing. What is everyone thoughts on using this? Should I go back to the bushing?

Thanks again

Randy


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Thursday, November 28, 2013 - 09:58 am:

A needle bearing is designed to run on a hardened surface. The drive shaft isn't hardened and you risk it'll wear prematurely.

The bearing close to the u-joint in the drive shaft doesn't have much load and a bushing works fine with just a little grease added now and then.

I've turned the outside of the bushing down to a slip fit just to be able to adjust the flange to the proper play without having to buy any expensive reamers. Then, when the fit was OK, I glued the bushing in place with epoxi.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Thursday, November 28, 2013 - 10:33 am:

With the Fun Projects pinion bearing you don't have to face the drive shaft bushing. I think most of the experienced guys will tell you that the needle bearing is a superfluous complication.


Posting is currently disabled in this topic. Contact your discussion moderator for more information.
Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration