Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Register Log in
  • Congratulations waross on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Pinion Depth Shimming 4

Status
Not open for further replies.
Autotecheng

Autotecheng

Automotive
May 6, 2012
11
Hi, I'm a mechanic learning about setting up differentials of the typical/basic type; open differentials with ring and pinion gear. Nothing fancy.

I am not sure I understand why there are pinion depth shims on the pinion shaft between the cone bearing and the pinion gear. But because there is a different amount of shimming on each differential I've seen I am guessing that there is a variance in the manufacturing process that is being compensated for.

I had thought maybe the pinion gear itself was the variable, but after extensive reading I've found a couple sources that say it is the housing that is the cause.

So my questions are:

Q1: what is the manufacturing process for the housing?

(ie cast from ductile iron, line bored for carrier bearings, bored for pinion bearings?)

Q2: What are the shims compensating for exactly?

Q3: Is there manufacturing variation in the depth of the pinion gear, ie the toothed portion?

Q4: Is there variation in the total depth of the pinion gear and shims?

I know that there are shims correcting a variation and that the correct pinion depth is important for proper gear contact but I have no idea which dimension is variable and which ones should be constant.

I'm sort of mind boggled as to whether the shimming stays with the housing or with the gears. It's often marked on the pinion gear but some sources claim it is specific to the housing, and the usual recommendation seems to be to transfer the old shimming to the new gears when doing a replacement.

Thanks for your help, apologies for any ambiguities about my inquiry and my long winded explanation.

-Andrew
 
Replies continue below

Recommended for you

Sort by date Sort by votes
1 varies depends on the diff
2 total dimensional stackup of tolerances for a given assy
3 yes
4 yes


I'm assuming you are working to a given endfloat or torque to turn when you shim

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
Upvote 0 Downvote
Are you may be referring to shim that goes on the pinion shaft behind the first bearing?

It's obvious you know the The pinion gear is made to function in a certain 3 dimensional relationship to the ring gear.

One of them is the dimension on this image called the "crown to crossing point"

relative to the ring gear centerline it is controlled by how housing is machined, and the combined tolerances of the cone and cup of the first "Timken" bearing. Assuming all housings or all bearings were, or are "the same" will get us in trouble.
 
Upvote 0 Downvote
Autotecheng-

Those are some excellent questions.

Q1- the manufacturing process for an automotive hypoid R&P housing can vary. Some are cast iron, some are cast aluminum, and some are even steel weldments. However, all have the bearing bores final machined for both pitch center and axial shoulder locations.

Q2- the typical pinion shims are used to adjust the heel/toe location of the mesh contact.

Q3- it is much easier to manufacture accurate R&P gear sets in mass production than producing accurate housings. That's why R&P gears come in matched sets. Pinion shims are the most expedient method of adjusting the R&P mesh contact location. The R&P gear teeth do typically have numerous subtle geometry mods to ensure that the mesh contact is optimized under loaded conditions.

Q4- I don't know if I understand this question. By definition, there will usually be some dimensional variation when using shimming.

Hope that helps.
Terry
 
Upvote 0 Downvote
Don't forget that, if adjustment is only provided for the pinion, then the most important consideration above all else is ensuring that the gear set has the required amount of backlash before setting the contact.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
 
Upvote 0 Downvote
It is much cheaper to take a little too much from the pinion gear housing and shim the pinion than to get it 'just right' and not be able to use a given pinion gear set. Now where did I leave that tube of prussian blue?
 
Upvote 0 Downvote
Nothing is manufactured perfect. In all types of machines where there are surfaces that act as load bearing, and that require a certain tolerance range for operating clearances, it has to be adjustable somehow. Also there is a consideration for pinion deflection under load, that makes it desireable not to have a perfect tooth contact pattern, under no load conditions.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

2009JKlover
  • Locked
  • Question
High pinion rear axle with reverse cut gears- design limitations
Replies
1
Views
637
BrianPetersen
BrianPetersen
KiwiME
  • Locked
  • Question
Coupling of EV Motor to Reduction Gear Pinion
Replies
12
Views
914
mfgenggear
mfgenggear
AX3L
  • Locked
  • Question
Measure the pinions of a truck
Replies
5
Views
255
tbuelna
tbuelna
forestgreen95gt
  • Locked
  • Question
Pinion Mass Dampener
Replies
12
Views
243
Fabrico
Fabrico
Mribeiro
  • Locked
  • Question
Dana 30 ring and pinion location
Replies
3
Views
158
Mribeiro
Mribeiro

Part and Inventory Search

Sponsor

Back
Top Bottom