Yukon Third Member replacement-HELP

Let me first start by saying i can turn a wrench but i am no expert on any of this and i need help. I have a 1973 dodge charger originally a 318 car was converted to a 440 with a mild cam and built internals. I have replaced all the wiring , breaks and other things since i have had it. The previous owner stated that it had a sure grip but the clutch pack was warn. Fast forward to this winter and i decided to replace the 3rd member with a Yukon one. I decided to go with the 3.91 ( i don't highway cruise it i just like spinning my tires ). So first issue the drive shaft, i could not remove it without take the caps off the u joint ( yes it was all the way into the trans housing ). So i got the old one out turns out to be a 2.73 and slapped the new one in with a bottle of friction modifier as recommended by YUKON, it had tapered bearings and the play seamed fine, rolled fine on stands. I go to take it out on a test and as soon as i turned it started binding and shaking, straitened out and it was fine. I did 10 figure 8's to see if it was just the oil needed to get into the LSD but no. So i added another bottle of friction modifier, same thing. I have driven it for 10-20 miles and there is no lessening of this issue. So my question is what's going on ? do i need to put thrust buttons in and re-adjust the axle play, could that even cause this issue ? do i need to go to green bearings ? I am scared to run it more and taking it out is a pain cause the drive shaft.

here are the specs on the 3rd member, i can post a video on you tube tomorrow too.

Yukon Dropout Assembly, Chrysler 8.75” Diff 489 Case w/Sure-Grip LSD, 3.90 Ratio

• Fits Chrysler 8.75” differential, 489 case
• Complete, fully assembled dropout
• 3.90 gear ratio
• 30 spline
• Upgraded with Sure-Grip/Powr-Lok clutch-type limited slip differential

I had to put 3 bottles in mine.
Only had a slight groan with 2 bottles.

Sounds like your drive shaft is to long.
You should of adjusted the axle end play when you replaced the center section.

This is definitely not a slight groan, you can see it shake the wheel you are turning in on. Drives strait no issue no noise

Maybe it's locked all the time acting like a spool? Check to see if the inside tire is hopping, while outside tire isn't.
I had a driveshaft that was too long once, but I could get it out with a little finagling. It would drive fine until quick acceleration, then it would vibrate the car.

its defiantly the LSD thats causing the issue ( will ONLY happen when turning) but why is my question .. and what the heck do i need to do to fix it .. i will pull the tire off and re-do the tension in the axle ( the pass axle tensioner) but would that cause the LSD to not work ? do i need to find those thrust buttons and put in ? i am at a total loss

Tapered bearings need the thrust button to set end play, but shouldn't cause this issue. I'm no expert, maybe someone else will know what's wrong. But I'd call Yukon and see what they say.

Yes if you have the clutch sure grip, and stock axle bearings, you need the buttons. Maybe that's the problem, the passenger axle is cranked in so far it's pushing on the clutches..

RemCharger said:

Yes if you have the clutch sure grip, and stock axle bearings, you need the buttons. Maybe that's the problem, the passenger axle is cranked in so far it's pushing on the clutches..

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it sounds like you have the axle adjustment too tight, try loosening a tad and see if that helps, if it does help, and you still get some noise loosen it some more till it's gone

It's new and shimmed aggressively. Put another bottle of additive in. My son got a sure grip unit from Dr diff and it was never a problem till we headed out on power tour. After hours on highway, stopped for gas turned at the light at bottom of the ramp, and sounded like the rear end was broken. It was not.