3.90 Gear pattern

[69superbee383]

What brand is that ring and pinion set btw?
I was considering to buy a set from DoctorDiff, they are cheap but i am sure they will sell good quality since this is their business.

I bought Richmond from summit. I’ve never bought from doctor diff but have read amongst the forums that they will steer you right.

 

[69superbee383]

Well I’m a little disappointed did my final assembly and pattern isn’t as good as when I did my set up. Must have been some variance between my set up bearing and the new one I pressed on. Still nice and centred between the face and the flank but moved down. I set backlash at .008 trying to move it up some no change. What do you guys say leave it or go back to the drawing board?

View attachment 1240737

Anyone else have any thoughts on this pattern my ocd and lack of ability to test drive is killing me.

 

[Wietse]

Anyone else have any thoughts on this pattern my ocd and lack of ability to test drive is killing me.

You are damn near the "by the book".
I have no experience with rear ends but with other types of transmission and reduction gearboxes and i would leave it like it is.

For your OCD i've left a shop manual snap shot

 

[joe smith]

Must have been some variance between my set up bearing and the new one I pressed on.

View attachment 1240737

I had the same thing happen when I did my pinion on my "9"... Kinda PO"s you when you think you pulled off a good one..

 

[69superbee383]

I had the same thing happen when I did my pinion on my "9"... Kinda PO"s you when you think you pulled off a good one..
View attachment 1241705

yup you got that right! I would feel much better if I could go for a drive and hear the rear end nice and quiet.

 

[TN Mopar]

What brand is that ring and pinion set btw?
I was considering to buy a set from DoctorDiff, they are cheap but i am sure they will sell good quality since this is their business.

I had my 8.75 rebuilt
I chickened out and paid someone for a rebuild with Warranty
I wanted the same gear set as the 3.91 I originally had
there was no 3.91 gear set for a 741 case
I had to go with the 489 case
the 3.90 gear he used was Yukon
my re-builder preferred them

 

[qkcuda]

My buddy who raced 8 3/4's for years always set them up shallow like that. His theory was when you applied power the load would move towards the center of the tooth.

 

[Wietse]

When applying load on the tapered pinion and ring in this application, the pinion wants to move in a forward direction and away from the ring gear.
The pattern is likely to move more towards the edge of the ring gear tooth and towards the heel end, which would be no problem for the OP his setup.

 

[dvw]

Go to page 13 https://www.yukongear.com/web_images/pages/Install Manuals/YukonKitInstallManual_Complete.pdf
You will see the toe/heal pattern means nothing. In fact talking to gear engineers you will find there is really nothing you can do to change it. If the backlash and pinion depth correct. Its a function of gear design and pinion height location in the gear housing itself.
Doug

 

[khryslerkid]

Wish I had that even of a pattern when I did this set. Some of these aftermarket sets can drive you nuts

What a goofy looking pattern!

Like Doug said, all you can do is get the pattern centered between the crown and the root. Heel and toe are a crap shoot. I tried every shim combination and set backlash from one extreme to the other. The housing can be at fault here as well as the ring and pinion manufacturer. So it is what it is sometimes.