New Yukon 3.91 489 - Cranky Pants noisy

[Titan1969]

Thanks in advance for any advice.
I purchased a new Yukon SG 3.91 case 489 for my 73 Cuda and removed the peg leg 3.23. I have swapped diffs many times and never encountered an issue, except this time.
Install went fine no issues, I 2x checked end play, added Valvoline 80/90 gear oil and friction modifier.
On the maiden voyage of a few miles in a straight line the diff has no issues, no noise, however any turning...even slightest I get alot of grinding noise and bumping, guesses the SG clutches are grabbing to much.
I attached a video and Ill calll Yukon this week for advice

 

[Titan1969]

cant find a way to upload 20meg video, so Ill report back what Yukon suggests.

 

[Katfish]

After my Dana gear change, things were clunky on corners.
Adding a 2nd bottle of the Ford friction modifier quieted things down.

 

[Challenger RTA]

cant find a way to upload 20meg video, so Ill report back what Yukon suggests.

Post the video on Youtube. Than paste the link here.

 

[Titan1969]

I spoke with Yukon and here was there feedback. I only have about 10 miles on the new diff, so it may need more breakin time. Im also going to add +4 oz Mopar Friction modifier before my next drive and Ill report back.

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We offer the OEM style HD Sure Grip - the aggressive Dana Spicer style 4 pinion Powerlock. These are patterned after the OEM Mopar Muscle car limited slips, but with updated/upgraded parts such as a stronger nodular iron case, chromo internals, etc. And like the factory HD Sure Grips, they are on the aggressive side.

The "smooth" street version uses the same clutch pack design and stack up as the old 440 and Hemi cars - so it is prone to a little noise and some tire scrub on the street - it is a true authentic reproduction - not a watered down design.

USA Standard Gear Powr Lok Positraction for Chrysler 8.75\" | ZP PC8.75-SMTH | RANDYS Worldwide

We also offer an even more aggressive version that is tailored to the pro touring / drag race crowd. It's not shy about letting you know it's back there, but it's the tightest unit out there this side of a spool.

USA Standard Gear Powr Lok Positraction for Chrysler 8.75\" | ZP PC8.75-AGRS | RANDYS Worldwide


with them being an authentic reproduction - they are an all steel clutch design - and WILL require some time for the clutch packs to break in.

my recommendation is to get it up to operating temp, find an open parking lot - do a series of 20 low speed tight circles in each direction. ( not doughnuts ) this will scrub the steel clutch packs together and rapidly break them in.

you should see a dramatic improvement right away - and it will continue to get better with more driving - but again - these are an aggressive unit - and will occasionally chatter / scrub tires.