Yep it works.

 

As long as its compatible with the Amsoil synthetic hypoid oil that said not to add LSD additive I guess it's OK.

Just curious. What's the theory to adding LSD additive to a non-LSD differential? Make the hypoid oil slipperier?

 

I dunno, but I've also seen threads about shudder when using no-additive gear oil, where using additive cured the problem. I didn't think of that in your situation, because I assumed the rear end would only chatter if turning.

When I got my first AAM axle equipped truck I called Redline to ask about this, and also about using 75-140 as I sometimes tow heavy, with grades and 105+ weather.

I got to talk to one of their engineers.

He basically said although the limited slip in Dodges isn't supposed to need additive, he would run the regular oil (that contains additives) as it wouldn't hurt anything, reduces friction and might run cooler, and the limited slip might be smoother.

He also said 75-140 would be fine and would give a bit if extra protection in hit climates and towing.

Maybe Dodge meant no need to add limited slip additive because GL5 synthetic you find in auto parts stores already contains enough?

Anyway it would be cheap and easy to try additive.

 

What the heck, then-

I'll try a bottle of LSD additive.

I used 75-140 Amsoil as I remember when I changed the fluid about 20k ago. It was thinner than regular 90wt hypoid as I remember at room temperature. I figured because it was thinner it couldn't hurt anything, especially if it offered the protection at high temps.

 

Buddy of mine had this issue and he used Amsoil 75w90 gear lube.
I am not sure what additive he used. It cured his problem. His truck was an 03'. His user name was Houndog on here. He has since passed away from Leukemia. It sucks.

 

Bobinyelm, I have a lurching in reverse if I try to back up with my 16000lb 5er on usually a slight rise. So bad sometimes that I stick it in 4WD high which cures it. I don't believe it is inside the bell. I changed out my u-joints in 2013 and the lurch was lessened under the same circumstances. When I place it in 4WD I believe the rear end does not "wind" up so much on the springs. I am going to install a track rod setup soon that will stop all torsional rotation on the rear diff housing. In the meantime I am going to change the rear oil and try Spoolers idea as this is a bit along the lines of what I believe the issue is.

 

After two FW surfacings and 2 new clutch assemblies, I tend to doubt it's inside the bell housing as well. I have since learned that Cummins/Dodge does not recommend resurfacing FWs more than 0.003", but I don't think that's my problem.

As with you, I replaced all of the U-Joints and the center carrier bearing assy, and it DID make a measurable difference (especially in the forward direction), which might give validity to the driveline/rear suspension cause.

Have you tried adding shims under the center carrier as Dodge issued in TSB 03-003-04 to fix the shudder? If you don't have that TSB, you can Google for the 4 page document.

My truck still has a Big Foot truck camper on the back, so I've done nothing since returning from a recent trip, but when I get the camper off, I plan to dig into it.

I don't have 4H or 4Low to try, so have to try to reduce the effect to a reasonable level. Mine does it even w/ a small, single axle 3000 pound trailer behind in reverse on a hard lawn surface, so I HAVE to improve it, or maybe break something from the truck literally jumping up and down no matter how smooth I try to be w/ the clutch, whether at idle, or a higher rpm feathering the clutch.

Keep me in the loop if you do some experimentation w/ yours and I'll do the same. Seems the ONE thing that is a SURE fix is a 1-Piece aluminum driveshaft, but having just dropped $350 to re-joint mine (all Spicer U-Joints and an OEM center bearing), I am not eager to drop almost $900 into a custom shaft (Dodge doesn't make one to fit the NV5600 transmission).

 

I feel that part of the problem is in a nv5600 reverse gear is to high. I had this problem with my truck and it went away after installing Dynatrac freespin hubs. Now when I backup a trailer I am in Low range and two wheel drive and there is no shudder. I do not know if the truck in question is a two wheel drive or a a four wheel drive. My truck is a short box (one piece driveshaft).

 

My truck is a long bed, quad cab 2WD so I am stuck w/ the gearing I have.

I used to have shudder in 1st and 2nd too, but so far, after the clutch, driveline, and trans mount, it's only in reverse (most only have it in reverse).

I have motor mounts and will try shimming the center bearing down, as well as LSD additive (though I don't have LSD).

I am waiting for nicer weather right now.

I am pretty sure the 1pc drive shaft is the ticket, but at $900 delivered, it's a bit spendy til I try everything else.

 

A 1 piece drive shaft is not an option with your 2wd, long bed quad cab.
Without a transfer case, the drive shaft would be much too long.

Even my QC, short box 2wd is pushing the limits for a 1 piece drive shaft.

 

I read several posts in other threads saying the factory makes a 1-pc aluminum driveshaft for the 3500 Quad Cab Long Bed 2WD equipped with the G56 transmission that can be shortened approx 1.5" and re-balanced to work w/ my NV 5600. My understanding is that from 2008-On the factory equipped these trucks w/ that driveshaft.
Driveline Specialists of Texas (http://www.driveshaftspecialist.com/) said they offer a custom 1-pc aluminum driveshaft for my '03 3500 Quad cab long bed pick-up with my NV5600 transmission. Perhaps the person w/ whom I spoke was mistaken, or misunderstood what truck I have.

Perhaps you are saying a 1-pc driveshaft is inadvisable, though they are certainly are said to be available (I have communicated with a gent who bought one for his '03 NV5600 QC LB 2WD from Doghouse Diesel a few years back, though they are now out of business..

Maybe I have been given false information about the current availability of 1-pc driveshafts for my truck from Driveline Spec.since you say they are not available, and you sound pretty sure of yourself.

They did say that I would have to remove the center bearing support bracket or it would contact the driveshaft when the suspension was deflected.

Given that you are likely correct, how do I correct my shudder problem?

I am not ready to drop the $900 quoted by Driveline Specialists, so if you have ideas other than I stated (shim the center bearing per the TSB, maybe install wedge-shims under my spring-pack above the diff) I am ready to listen.

Thanks,
Bob

 

Bob,

By coincidence it was Rich at Doghouse diesel that had a maximum single piece driveshaft length spec on their website.

If I recall, the max length was 79" U-joint ctr to ctr. I measured my truck (2wd, short box, quad cab, NV5600) at 77".

Your identical, but long bed 2wd qc truck, would require a driveshaft nearly 2 feet longer than mine.

All the single piece driveshaft discussions are for 4wd trucks with a transfer case.
I've never seen nor heard of a 1 piece factory driveshaft for a Dodge Cummins quad cab or mega cab 2wd truck.

The G56 manual transmission cannot accomodate a singe piece driveshaft in 2wd form (without a transfer case attached to it) since it does not have a slip yoke output shaft/tail housing.

My 2wd truck, with a NV5600 trans and 3.73 rear gears, gets a little rough backing up our 10k lbs 5th wheel.
It's mostly due to my Southbend DD aftermarket clutch.
I keep the rpm's up and slip the clutch a little.
It's a compromise that I'm willing to live with...

 

Sir,

My apologies to you.

I have re-checked, and although at one point Doghouse Diesel DID apparently sell some 1-Pc driveshafts they adapted for my 2WD LB QC trucks from later OEM aluminum, neither Driveline Specialists of Austin, TX nor Inland Empire Driveshaft of Corona, CA make, or recommend a 1-PC driveshaft for my truck.

I spoke to Bud in TX (who said he supplied a lot of Doghouse's shafts except for the OEM ones they modified, like for my truck), and Jeff in CA, and both said 88" is about their limit (my shaft is about 97.5" long).

Bud suggested possibly a broken U-Bolt on my rear spring pack that is invisible except to actually SEEING movement under load, and Jeff suggested filling the new OEM center carrier bearing assembly (the voids in the rubber mount) with silicone RTV rubber to reduce "flex."

Bud also said he's seen this with the G56 dual-mass flywheel, but not w/ the solid one on my NV5600 transmission. Having had the flywheel checked and finished twice to tight tolerances, with 2 new clutch kits, that cause seems most likely, either, though he said he doubted that before the truck was really under way (and the driveline spinning) he still couldn't help thinking clutch.

Reading the Forums, however, mine is HARDLY the only one that shook so badly the cab jumped up and down. The investigation continues.