ss4chad

iTrader: (19)

2013 Sierra 1500 SLT, 6L80 with a brand new Circle D 2800 stall, new Yukon Dura Grip with Richmond 3.90 gears.

When I am stopped on a slight incline, I can feel a shutter when I make a right or left turn. Sometimes at low speed and low RPM's I can also feel it a little bit of a shudder (maybe) and there is a low pitch humming noise. I can give it gas and it goes away with a gear change. From a dead stop I can floor it and it performs normal and if the road is flat I can make the right and the shudder is as noticeable.
Trans had 89K when I added the converter, new pan with drain plug, new Tru-Cool Max HD Cooler and the fluid has been flushed 3 times since new components installed. Trans has 101K as it sits.
The rear end had 89K when I replaced the new Diff, all new bearings & seals including axle bearings & seals. Have flushed the rear twice since new components installed with fresh synthetic oil but DID NOT add Friction Modifier. The Mobil One 75-90 Gear Oil says it has the stuff needed for the positrac.
Could this shutter be an easy fix by adding the friction modifier?
Or is it something bigger? U-Joints, Loose Carrier, Transmission, Converter?

Merry Christmas!
Chad

3wide

I have this unit in my truck, I use Mobil 1 and an additive. In their paperwork it also states GL-5 gear oil and their additive. I believe the additive will get rid of the chatter that you are experiencing.

BigKID

iTrader: (5)

Synthetic is no-bueno for the clutch style differentials. Put some dino 80-90 and the delco friction additive in it. Or just live with the shudder till it burns the clutches enough to slip completely. I have tried the gear oil that supposedly had the additive but was not happy with it. Dumped a tube of the parts store additive it and seemed to help but not as good as the Delco stuff.

That type of differential is torque sensitive on the apply so why you notice the chatter more on an incline rater than on flat or decline at the same acceleration rate. More throttle is required thus more torque to the differential. Same would happen if more throttle was applied on a flat turn but at a higher rate of acceleration. Tire friction also factors in here. More tire friction will allow the clutches in the differential to slip, less tire traction will allow the clutches to fully engage and spin the inside tire.

RedXray

I've been using the F@&d stuff in my Yukon DuraGrip with success. My guess most all of the "friction modifiers" come from the same manufacturing plant. I do know one thing... if you get some on your clothes you'll have to toss them. If you get some in your hair or on your skin... no pootang whatsoever until the stench wears off

ss4chad

iTrader: (19)

Put in Lucas HD 80-90 and Yukon Friction Modifier and the shudder went away!!
You guys are awesome!!

Chad