8 3/4 diff/axle noise in Reverse

[MJFUR]

I've had multiple threads on the 8 3/4 axle in my 69 Chrysler 300, rebuilt multiple times for multiple problems by multiple "Experts" all within about 4k miles. Here's the next problem.

Originally a 2.76 open axle with a 489 third member. Converted to a 3.23 Sure Grip with parts from Doctor Diff.. After continuous gear whine and multiple remove, inspect, re-installs the 489 with Dr. Diff parts was swapped out for a 742 with OEM parts in it. Gear whine now gone.

Now when backing up in Reverse with the steering wheel full right (counter clockwise circles) the diff/axle pop, buck and make noise. Reversing in the other direction (clockwise) is smooth with no noises. Driving tight circles in Drive (either right or left) are smooth as well.

Where's my problem?

Thx

 

[Toolmanmike]

Is it a sure Grip unit and if so, did you add Friction Modifier to the lube?

 

[Big_John]

I've had multiple threads on the 8 3/4 axle in my 69 Chrysler 300, rebuilt multiple times for multiple problems by multiple "Experts" all within about 4k miles. Here's the next problem.

Originally a 2.76 open axle with a 489 third member. Converted to a 3.23 Sure Grip with parts from Doctor Diff.. After continuous gear whine and multiple remove, inspect, re-installs the 489 with Dr. Diff parts was swapped out for a 742 with OEM parts in it. Gear whine now gone.

Now when backing up in Reverse with the steering wheel full right (counter clockwise circles) the diff/axle pop, buck and make noise. Reversing in the other direction (clockwise) is smooth with no noises. Driving tight circles in Drive (either right or left) are smooth as well.

Where's my problem?

Thx

I had something similar happen. It would only happen on sharp left turns going forward.

I had used a gear oil that supposedly didn't need an additive for the sure grip. After checking around, and doing some reading, the consensus seemed to be to try changing the oil first. In fact, if you read the FSM or any of Chrysler's service training, they say that is the fist thing to try.

The cure was to change the fluid and add Ford LSD additive. https://www.amazon.com/gp/product/B000NU5LP6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 No problems since.

I pumped it out with a suction pump and refilled without any disassembly.

 

[polara66hardtop]

I had something similar happen. It would only happen on sharp left turns going forward.

I had used a gear oil that supposedly didn't need an additive for the sure grip. After checking around, and doing some reading, the consensus seemed to be to try changing the oil first. In fact, if you read the FSM or any of Chrysler's service training, they say that is the fist thing to try.

The cure was to change the fluid and add Ford LSD additive. https://www.amazon.com/gp/product/B000NU5LP6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 No problems since.

I pumped it out with a suction pump and refilled without any disassembly.

my buddy with a 79 camaro had the same problem, and a ford friend of mine recommended the ford additive. It cured that very same problem,,,good product!

 

[MJFUR]

I had something similar happen. It would only happen on sharp left turns going forward.

I had used a gear oil that supposedly didn't need an additive for the sure grip. After checking around, and doing some reading, the consensus seemed to be to try changing the oil first. In fact, if you read the FSM or any of Chrysler's service training, they say that is the fist thing to try.

The cure was to change the fluid and add Ford LSD additive. https://www.amazon.com/gp/product/B000NU5LP6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 No problems since.

I pumped it out with a suction pump and refilled without any disassembly.

Thx. I'll give it a try.

 

[66 Monaco 500 365]

Same issue with a 742 and Dana Power lock.
it took 2 bottles of additive, but it worked smoothly after that.
I ran that diff with slicks and a 440 6bbl running 12 flat, worked perfectly.