Proper Rear end specs??

Discuss all things Model T related.
Forum rules
If you need help logging in, or have question about how something works, use the Support forum located here Support Forum
Complete set of Forum Rules Forum Rules
User avatar

Topic author
Doug Keppler
Posts: 162
Joined: Sun Jan 06, 2019 2:28 pm
First Name: Douglas
Last Name: Keppler
* REQUIRED* Type and Year of Model Ts owned: 1924 Touring
Location: Fredon N.J.
MTFCA Number: 49716
Board Member Since: 2016

Proper Rear end specs??

Post by Doug Keppler » Sat Jun 29, 2019 9:48 pm

I'm currently rebuilding my rear end and using Chaffins manual. I'm wondering why there wasn't a shim selection chart ever made so you would know what size shim to install under the ring gear. Meaning, if you had .030 backlash between ring and pinion, what size shim would you need to get .012
1924 Touring car
There's No Substitute for Proper Lubrication


Scott_Conger
Posts: 6428
Joined: Sun Jan 06, 2019 11:18 am
First Name: Scott
Last Name: Conger
* REQUIRED* Type and Year of Model Ts owned: '13, '15, '19, '23
Location: Clark, WY
Board Member Since: 2005

Re: Proper Rear end specs??

Post by Scott_Conger » Sat Jun 29, 2019 10:15 pm

Doug

you don't ever want to shim the ring gear
Scott Conger

Tyranny under the guise of law is still Tyranny

NH Full Flow Float Valves
Obsolete carburetor parts manufactured

User avatar

Mark Gregush
Posts: 4956
Joined: Sat Jan 05, 2019 1:57 pm
First Name: Mark
Last Name: Gregush
* REQUIRED* Type and Year of Model Ts owned: 1925 cutdown PU, 1920 Dodge touring, 1948 F2 Ford flat head 6 pickup 3 speed
Location: Portland Or
MTFCA Number: 52564
Board Member Since: 1999

Re: Proper Rear end specs??

Post by Mark Gregush » Sat Jun 29, 2019 10:22 pm

Most of this is trial and error. There is no chart of what shim to use. It is a lot of taking apart and fitting the bronze thrust washer to get the proper clearance between the ring gear and pinion, then fitting the other side of the case to get preload. Oh if you have that much clearance you need different bronze and steel thrust washers.
Last edited by Mark Gregush on Sat Jun 29, 2019 10:24 pm, edited 1 time in total.
I know the voices aren't real but damn they have some good ideas! :shock:

1925 Cut down pickup
1920 Dodge touring
1948 Ford F2 pickup

User avatar

Topic author
Doug Keppler
Posts: 162
Joined: Sun Jan 06, 2019 2:28 pm
First Name: Douglas
Last Name: Keppler
* REQUIRED* Type and Year of Model Ts owned: 1924 Touring
Location: Fredon N.J.
MTFCA Number: 49716
Board Member Since: 2016

Re: Proper Rear end specs??

Post by Doug Keppler » Sat Jun 29, 2019 10:24 pm

Why not Scott? They tell you to do it in the manual
1924 Touring car
There's No Substitute for Proper Lubrication

User avatar

Henry K. Lee
Posts: 5339
Joined: Sun Jan 06, 2019 11:09 am
First Name: Henry
Last Name: Lee
* REQUIRED* Type and Year of Model Ts owned: Many
Location: South Pittsburg, TN
MTFCA Number: 479
MTFCA Life Member: YES

Re: Proper Rear end specs??

Post by Henry K. Lee » Sat Jun 29, 2019 10:44 pm

Principles of Geometry states, "by finding the two planes of contact (degrees), fill differential differences by loss plus degree of required mass". Reference: Pg #123.

Add the two ring gear shims with red Loc-tite, reset gear lash by paper shims until desired tolerances are attained. Or by new ring and pinion gears. I thought you and I covered this a couple of hours ago? Uhmmmmm!

Hank ????


Altair
Posts: 365
Joined: Thu Jan 17, 2019 11:52 am
First Name: David
Last Name: Menzies
* REQUIRED* Type and Year of Model Ts owned: 1926 Touring and 1915 Touring both Canadian models
Location: British Columbia
MTFCA Number: 27825
Board Member Since: 2012

Re: Proper Rear end specs??

Post by Altair » Sun Jun 30, 2019 10:16 am

I don't think there ever was any rear end specs they were assembled to a general clearance, any thing up to .040 and filled with #2 grease. We try to match modern clearances to day of .005 which is difficult to attain and then put in varying grades and weights of oils in the housing when there were no oil seals available. Grease was put in the housing and the outer rollers were lubed with a manually turned grease cup. I don't think there are two guys with the same process for a differential housing assembly to day. Crown gears are never true they may vary .005 and must be set to the highest point, if it is too tight you will get a pulsating howl. Even modern crown gears are not true, all four quadrants must be checked and set to the highest point. They are machined true while soft then they warp when hardened.


Original Smith
Posts: 3284
Joined: Tue Jan 08, 2019 10:43 am
First Name: Larry
Last Name: Smith
* REQUIRED* Type and Year of Model Ts owned: 13 Touring, 13 Roadster, 17 Coupelet, 25 Roadster P/U
Location: Lomita, California
MTFCA Number: 121
MTFCA Life Member: YES
MTFCI Number: 16310

Re: Proper Rear end specs??

Post by Original Smith » Sun Jun 30, 2019 9:50 pm

The first problem you have is you are using Chaffin's book. The only manual to use is the original Ford service book, either original or a copy.


Allan
Posts: 5201
Joined: Sun Jan 06, 2019 7:21 pm
First Name: Allan
Last Name: Bennett
* REQUIRED* Type and Year of Model Ts owned: 1912 van, 1917 shooting brake, 1929 roadster buckboard, 1924 tourer, 1925 barn find buckboard, 1925 D &F wide body roadster, 1927LHD Tudor sedan.
Location: Gawler, Australia

Re: Proper Rear end specs??

Post by Allan » Mon Jul 01, 2019 5:05 am

If the bronze thrust washers are machined to the correct thickness, there is no need for shims. If the clearance is not that which is desired, it can be altered by shuffling the steel discs from side to side. Once the desired clearance is achieved, the right half and its washers can be assembled, the gap between the housings measured, and the second bronze thrust machined to fit.

Hope this helps.
Allan from down under.

Post Reply Previous topicNext topic