Detroit TrueTrac issue?maybe?

[1970mule]

Hello,

Long time no post for me, that is a good thing i guess. The bronco has been running well. However, i recently blew up the mini spool i had in the rear. I bought a detroit TrueTrac and had a shop install it in the third member that i removed a brought to them. So. After i installed the 3rd member they setup for me i am getting a bad vibration starting at 25-30 mph and getting progressively worse from there. The shop said use synthetic diff oil, so i did. After the issue i read that i shpuld not. Could the oil be the cause of all this. What could be the problem? Thanks in advance.

 

[Jebus]

I would first recheck the reinstallation of the driveshaft...

 

[cofferjl]

i second checking the driveshaft. Did you phase the driveshaft the same way it came off? Is the u-joint setting correctly? Did everything go back correctly when you reinstalled axle shafts? Those are the places I would start. I can not see the oil causing this issue being synthetic or not. It is possible that the third member wasn't set up correctly, but I would start with the easy things first.

 

[nickgp]

I also agree on checking the driveshaft.

 

[bronconut73]

Driveshaft phasing position.

 

[Nothing Special]

Synthetic oil in a TrueTrac will reduce its effectiveness, that's why it's not recommended. It won't cause vibration.

 

[Apogee]

Synthetic oil in a TrueTrac will reduce its effectiveness, that's why it's not recommended. It won't cause vibration.

Plus, the TrueTrac isn't doing anything when driving in a straight line at 25-30 MPH anyway, so driveshaft is sounding more and more likely. As for the lube, the uniformity of the molecules in synthetic lubes leads to thinner films with higher shear strengths, so the inherent friction needed for the helical torque biasing gears to do their job is reduced andthe unit becomes less effective, but it shouldn't damage anything.

 

[Rustytruck]

make sure the driveshaft bolts are not too tight and the splines are not bound up. while the shaft is out check the transfer case yolk and the axle yolk are not wiggly. check all u-joints and the centering ball in the driveshaft and grease well. make sure you block your tires with the driveshaft out.

http://www.randysdriveshaft.com/torque.html

if you don't have a torque wrench that will fit in the space needed. it is about snug with a short wrench. blue loctite should be used on the clean hardware.

 

[Timmy390]

check the transfer case yolk and the axle yolk are not wiggly

This....^^^^^ I suspect the pinion bearing preload

A quality, petroleum-mineral based, GL5 rated 80w-90 gear oil should be used.
Synthetic oils are not recommended for Truetrac applications. While some customers have found that synthetic oils works well in this application, Eaton has not confirmed under test conditions that all synthetic oils are compatible with Detroit Truetrac applications.
Friction modifiers should not be used because they will decrease performance (reduce differential bias).

Tim

 

[1970mule]

Alright thanks fellers, i am goimf to take the drive shaft to the shop in a few. The yolk on the t-case did not uave any slop in it like side to side or up and down. But maybe preload. Matbe a little slop before i fekt the gears engage. I was tjinking maybe i over tightened the u-bolts but i losend them. One more question, why would i get vibration if i only swapped out the diff stuff drive shaft never came out, just got disconnected where it connects to the third member? Thx again

 

[Rustytruck]

did you separate the splines on the drive shaft. if you did maybe didnt get them back together properly? u-joints must be in phase to work properly. one spline off could cause issues. did you remove the rear housing? maybe u-bolt issues. were are grabbing at straws as you are the only one who knows what has been done since the last time the Bronco operated properly. How loose sided to side are the u-joints in the yolk saddles? can the drive shaft be pushed off center due to yolk wear?

 

[Rustytruck]

are your front hubs unlocked? truck in 2wd?

 

[Nothing Special]

did you separate the splines on the drive shaft. if you did maybe didnt get them back together properly? u-joints must be in phase to work properly. one spline off could cause issues....

U-joint phasing isn't a factor with a CV joint at one end of the driveshaft though

 

[DirtDonk]

Yes it is. ALWAYS...
The CV aspects of the double-cardan can't overcome an out-of-phase condition when we're talking about rotational phase (if that's a way to phrase it?) where it's very forgiving of the angles being off, it won't do anything for the single joint being rotated one spline or more out of it's original alignment.
Or a better way to put it I suppose, would be if the caps have become mis-aligned. Nothing to do with the angles.

So no, you still can't get a double-cardan shaft out of phase and not have it do all the bad things a single cardan shaft would do. Seen it several times.

Paul

 

[DirtDonk]

Sorry, maybe I should have said "it has not made a difference in my experience" whereas there may be some theoretical aspect that says it does not matter what position the single joint is at, as long as you have a properly working CV joint.
But my experience has been that it's very annoying when the slip yoke has been put together one spline off.;D

Paul

 

[sprdv1]

Good luck. Tackle one suspect at a time

Alright thanks fellers, i am goimf to take the drive shaft to the shop in a few. The yolk on the t-case did not uave any slop in it like side to side or up and down. But maybe preload. Matbe a little slop before i fekt the gears engage. I was tjinking maybe i over tightened the u-bolts but i losend them. One more question, why would i get vibration if i only swapped out the diff stuff drive shaft never came out, just got disconnected where it connects to the third member? Thx again

 

[sprdv1]

LOL.. right

Sorry, maybe I should have said "it has not made a difference in my experience" whereas there may be some theoretical aspect that says it does not matter what position the single joint is at, as long as you have a properly working CV joint.
But my experience has been that it's very annoying when the slip yoke has been put together one spline off.;D

 

[1970mule]

are your front hubs unlocked? truck in 2wd?

I am pretty dure the ate not locked, the locking hubs are busted so i leave it in 2wd. Thx

 

[1970mule]

I have not taken the slip yolk off so it should be aligned.

 

[1970mule]

Update, well vibration is gone. Overhauled the drive shaft with new balance. But i did have the front hubs locked. I set them to free before i drove next. I'll lock them up tomorrow and see if it was that simple. Thx