So i recently changed the fluid in my rear end (85-145 full synthetic) i checked around and was told that 4oz. of friction modifier was the proper amount to add to my rear dif. and i did so, problem is i am now getting a lot of wobble out of the rear end (this started about 3-4 days after changing fluid) and honestly feels like something is a little loose, the only other thing i could think of is the pinion bearings, and honestly they aren't that sloppy....any ideas, did i use too much modifier?all wheel lugs are torqued, tolerances were tight in the dif. when i had it apart last week (minus the slight play in the pinion but it was like that and didn't cause a wobble prior to this) drum brakes are good, wheel bearings are good, no play in 'em.....:shrug:thanks guys, Matt.

this might be just coincidence but i had a wobble in my rear end for a few months and could not isolate it until i let my buddy borrow my truck to tow a porsche to north ms. he brought back and told me there was a bad vibration in the truck and he feared going over 55 mph on the return trip. i laughed and said the vibration had been there for quite som time. went to the store and though the dash was fixing to fall off it was shaking so bad. got out and could see a broken belt in the tire, i had just balanced these tires and didnt see it. changed tires and shot down the freeway 95 mph and smooth as glass. is the rear end making any howling noises or clunking when changed from forward to reverse?

nothing caught in the tire unfortunately... it does have a slight knock when shifted into gear, thats what prompted me to start looking into it in the first place. i checked the pinion first as i know a "clunk" is a tell tale sign. i raised the rear end and fiddled with it a bit, all and all play isn't too bad, i meant to change it out last weekend while while i was changing the gear lube but the parts store (lets just call them shmrucks as to not demonize the actual company) told me they had the part...in stock!! latter that week, not only do they not have the parts on hand, their warehouse is out of the outer bearing....napa on the other hand had the parts but they were almost a week out and nearly 1-1/2x the price, needles to say im waiting for the other guys to get the parts in....

I take it you checked the rear u-joint, FYI the friction modifier i only if you have a limited slip diff(adding to a regular diff would'nt hurt) and if you going to swap to a manual at least go with the NV5600.

yup, checked all the universals, thanks.....an nv5600?? why is a six speed any better than a 5!?!?! especially when production has all but stopped and dealers don't even have parts?.....i can see it now..."finally got that 6 speed in"...."oh dang, i broke my 6 speed"....."hi dealer, do you have any parts?? you are my last hope"....dealer replies "NO!! you shouldn't have put in a 6 speed, now scrap the nv5600 and put in your tired old 47re!! MUAHAHAHA!!!!!":ahhh:.....no thanks! besides, i already have a NV4500 for the thing (can't beat free)

....an nv5600?? why is a six speed any better than a 5!?!?! especially when production has all but stopped and dealers don't even have parts?.....i can see it now..."finally got that 6 speed in"...."oh dang, i broke my 6 speed"....."hi dealer, do you have any parts?? you are my last hope"....dealer replies "NO!! you shouldn't have put in a 6 speed, now scrap the nv5600 and put in your tired old 47re!! MUAHAHAHA!!!!!":ahhh:.....no thanks! besides, i already have a NV4500 for the thing (can't beat free)

i feel the exact same way. the jump between 3rd and 4th is quite large, but never changes. my driving style has adapted to it. i have ran in to a lot of people selling their cummins because of all the rowing of the stick. it doesn't bother me. and the NV4500 is plenty strong for the CGVW the truck was made for.

NV5600 a lot heavier trans,parts are readily available through several outlets,Blumenthals in OKC,Inland Truck parts as well as others( i never buy from Dodge). But maybe you never tow any real weight.FYI New Venture went belly up they don't produce the the NV4500 anymore, in fact the NV5600 replaced the NV4500

How did you check your u-joints? You need to physically remove the drive line to see if they are binding up or have a rachety feeling. Just had one on my 05 that would not move a stitch while pushing and pulling on it and it showede no signs externally visual of being bad but upon removal of the shaft it was so dry and bound up I couldn't move it by hand without a bar or pliers.