Differential setup

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Scott Vincent

Junior Member
Joined
Aug 28, 2022
Posts
21
Reaction score
23
Location
Sierra Vista, AZ
First Name
Scott
Truck Year
1974
Truck Model
K20
Engine Size
350 B30over
Hey fellers...need some insight and opinion here...take a look at these pics and you fellas tell me where you think I'm sitting. Backlash is already at around 5 thousandths...just trying to get contact pattern in the green.
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
 

TPISly-C10

Full Access Member
Joined
Apr 1, 2019
Posts
615
Reaction score
878
Location
Boucherville QC Canada
First Name
Sly
Truck Year
1986
Truck Model
C-10 shortbox
Engine Size
LQ4 6.0L
look good to me...on mine i backlash at 7 thousand
 

Attachments

  • _DSC3578.jpg
    _DSC3578.jpg
    103.4 KB · Views: 57

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
28,956
Reaction score
23,468
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
Looks like it "might" be just a touch deep into the tooth, but kind of hard to tell with the thick marking paint. In my unprofessional opinion, I'd say it's good.
 

Curt

Full Access Member
Joined
Sep 11, 2017
Posts
676
Reaction score
1,140
Location
Loco Hills
First Name
Curt
Truck Year
1984
Truck Model
K-30
Engine Size
383
I like it.It needs to have more resistance as you turn and check the pattern.

Even with 5 thousandths of backlash,you have to put out.Leather gloves or a rag.
 

Curt

Full Access Member
Joined
Sep 11, 2017
Posts
676
Reaction score
1,140
Location
Loco Hills
First Name
Curt
Truck Year
1984
Truck Model
K-30
Engine Size
383
Janz Engineering on YouTube.Master of ring and pinion.Even the pro racers and rock bouncers use his methods
 

Turbo4whl

Supporting Member
Supporting Member
Joined
Oct 30, 2019
Posts
2,837
Reaction score
6,356
Location
Downingtown, PA
First Name
Wayne
Truck Year
1974
Truck Model
Jimmy
Engine Size
350
I like it.It needs to have more resistance as you turn and check the pattern.

Even with 5 thousandths of backlash,you have to put out.Leather gloves or a rag.

This is very important. You must add a load when checking the pattern. Another way to achieve this is to take a pry bar between the gear housing and the smooth side of the ring gear. Turn the pinion nut with a wrench, making sure you are rotating the pinion gear into the drive side of the ring gear.

You must be registered for see images attach
 

CalSgt

Full Access Member
Joined
Oct 3, 2021
Posts
1,471
Reaction score
3,057
Location
CA
First Name
Casey
Truck Year
1980
Truck Model
Chevy K-10 Custom Deluxe
Engine Size
350
I like it.It needs to have more resistance as you turn and check the pattern.

Even with 5 thousandths of backlash,you have to put out.Leather gloves or a rag.

This is very important. You must add a load when checking the pattern. Another way to achieve this is to take a pry bar between the gear housing and the smooth side of the ring gear. Turn the pinion nut with a wrench, making sure you are rotating the pinion gear into the drive side of the ring gear.

You must be registered for see images attach

^^^^ This

It’s hard to get an accurate reading without simulating a load on the gears. We tap a punch in between the edge of the ring gear and the diff housing at top or bottom depending on which direction it is rotating. Be sure to run it through in both directions so you can inspect the drive and coast side. I’ve had to compromise on patterns based on drive Vs. coast pattern to keep them both acceptable.

You can also thin the patterning paste with a little bit of ATF so it isn’t so thick.

Just as important as “where” the contact patch is, is the “shape”. It should be a gentle transition from where the gears first connect to where the paint is totally wiped clean. There shouldn’t be any real sharp lines at the leading and tailing edges.
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
28,956
Reaction score
23,468
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
How can y'all tell that he didn't put a load on it as it was rotated?
 

Turbo4whl

Supporting Member
Supporting Member
Joined
Oct 30, 2019
Posts
2,837
Reaction score
6,356
Location
Downingtown, PA
First Name
Wayne
Truck Year
1974
Truck Model
Jimmy
Engine Size
350
How can y'all tell that he didn't put a load on it as it was rotated?

Where the OP put the marking paste, the pattern should show as the metal gear. All the paste forced out exposing the gear tooth. Instead you are seeing the footprint of the paste collected on the pinion gear.
 

Curt

Full Access Member
Joined
Sep 11, 2017
Posts
676
Reaction score
1,140
Location
Loco Hills
First Name
Curt
Truck Year
1984
Truck Model
K-30
Engine Size
383
Jantz Engineering,I apologize.His channel has a videos that explains exactly where you want your pattern.

@bucket,I can see that real pressure wasn’t applied to the marking compound by how faint it is.

Someone mentioned thinning it out,and that’s exactly right.I learned this later after setting up a couple gear sets.

The bigger axle assemblies take quite a bit of resistance to see a good pattern.The last 14 bolt I did,I used a plastic hammer to pry against the ring gear.

This job is so much easier with 2 people.
 

Scott Vincent

Junior Member
Joined
Aug 28, 2022
Posts
21
Reaction score
23
Location
Sierra Vista, AZ
First Name
Scott
Truck Year
1974
Truck Model
K20
Engine Size
350 B30over
Ok...well considering that Iʻm a rookie in this realm...it sounds like most of yaʻll are saying I should clean off the existing compound, buy some new compound, which apparently Iʻm gonna have to go through Amazon to do instead of being able to get it today :(, thin out my compound with ATF, and run a new pattern with some type of resistance to the gears. Is that right?

I mean with what Iʻve got right now am I good? Can I run this without issues? This part is a little more intimidating than I expected and I was really hoping it was good.

And I just started finding a bunch of stuff for making my own compound...is this safe to do?... because if Iʻm gonna do this Iʻd rather make my own instead of paying $15 for 1 oz. of this ****.
 
Last edited:

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
28,956
Reaction score
23,468
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
You haven't changed any settings, so maybe just apply pressure and run it again? I haven't checked the pattern on much stuff either, so maybe that won't get a cleaner result.
 

CalSgt

Full Access Member
Joined
Oct 3, 2021
Posts
1,471
Reaction score
3,057
Location
CA
First Name
Casey
Truck Year
1980
Truck Model
Chevy K-10 Custom Deluxe
Engine Size
350
Ok...well considering that Iʻm a rookie in this realm...it sounds like most of yaʻll are saying I should clean off the existing compound, buy some new compound, which apparently Iʻm gonna have to go through Amazon to do instead of being able to get it today :(, thin out my compound with ATF, and run a new pattern with some type of resistance to the gears. Is that right?

I mean with what Iʻve got right now am I good? Can I run this without issues? This part is a little more intimidating than I expected and I was really hoping it was good.

And I just started finding a bunch of stuff for making my own compound...is this safe to do?... because if Iʻm gonna do this Iʻd rather make my own instead of paying $15 for 1 oz. of this ****.
I’m assuming you used all of the marking compound already…

Take the brush and smear the pattern marks over with the stuff left on the ring gear.

Yes you can make your own too, I think we used some titanium dioxide (white oil paint base) and just thinned it down. It’s thicker than bearing grease otherwise.

ETA: you don’t HAVE to thin the marking paste but it makes it go farther and easier to use
 

Scott Vincent

Junior Member
Joined
Aug 28, 2022
Posts
21
Reaction score
23
Location
Sierra Vista, AZ
First Name
Scott
Truck Year
1974
Truck Model
K20
Engine Size
350 B30over
Set it up the same...thinned it and added resistance for better marking...here's what I got. Tell me what you guys think now.


You must be registered for see images attach
You must be registered for see images attach
 
Last edited:

Latest posts

Forum statistics

Threads
41,854
Posts
903,558
Members
33,367
Latest member
texdave
Top