Robofig

Truck and trans runs great empty after the swap.

When I tow a trailer, 3000 to 6000 lbs, and I throttle down fairly hard to get the load moving, I get a real bad vibration.

I think I have the trans/t-f case at the wrong height on the cross member.

I screwed up and forgot to take measurements of where the rear output was when I had the auto in the truck.

Can anyone help me out? Anyone with a NV4500 give me some measurements?

I have an angle gauge if anyone can help me with some angles.

Thanks in advance.

PapeCAT

If you have a protractor then ensure your Output Yoke is Parallel to your Rear Axle input Yoke and go from there... You can either Shim the rear axle - or move the trans/xfer case up or down or both.

Yokes NEED to be parallel. Your ujoints aren't going to last long at this rate...

I have built a custom crew cab diesel with two yoke shafts + front and rear driveshafts so speaking from experience here...

Your problem is definitely workable.

Robofig

So the 2 yokes need to be parallel or equal angles. And that is while the truck is empty.

Mike Mc

That is caused from rear axle wrap up. It's changing the rear drive line angle so the U-joints are no longer in sync.

To test my theory, temporary put it in 4x4 so torque is transfered to the front also. This should help reduce rear axle wrap up. If you determine rear axle wrap up is the problem you need traction bars that hold the axle at the same degree all the time.

Robofig

[QUOTE=Mike Mc;2995967]That is caused from rear axle wrap up. It's changing the rear drive line angle so the U-joints are no longer in sync.

I changed out the auto trans for a 5 speed manual.
With the auto trans this problem didn't occur.

I think I will check the yoke angles.

Mike Mc

Even if you changed your drive line angles with a shorter or longer drive line the engine and rear end should still be sitting at the same degree as before (unless you changed it during the swap). If they are not at the same degree, example, engine 2 deg. rear end 3deg. it should give a light in and out buzzing vibration at highway speeds.

Now that you switched to a manual transmission you have shorter gears and direct drive. This applies more torque to the rear end when the engine hits it's power = axle wrap. With an auto having a slipping torque converter and longer gears it absorbes the engine hit.

With you having a load the truck can't lunge forward so the axle twists in the leaf springs giving you the viberation under load.

Robofig

I understand what you are saying.

So does this mean every 1st gen 4x4 with a 5 speed (getreg) have the same problem from the factory?

Would drive shaft phasing possibly cause this?

Robofig

BUMMMMP

any one have any ideas?

Mike Mc

Have you tried firm acceleration in 4x4 with a load yet?

PapeCAT

Have you checked yoke angles yet?????

Robofig

I found the problem.

I ended up lowering the carrier bearing an inch and a half and it took out 90 percent of the problem.

This weekend I will drop it a little more and see what happens.

cj360trider

i had the thot of the driveline being out of phase. you might check that jus to make sure

Robofig

The drive line is new from the shop and in phase