Hey there,

Since the 4l60 --> 4l80 I've had a minute vibration above 45 mph, and by 80 it's humming pretty good. Driveshaft length is good, and the yoke isn't too far in the tailshaft housing.

I measured the driveshaft angles (2 pc. driveshaft) and came up with the following:

Trans -7 degrees
Shaft #1: -3 degrees
Shaft #2: -5.5 degrees
Pinion: +3 degrees

negative means it's pointing down, positive it's pointing up.

At this point I'm not sure what I need to shim to get things back in line. I'd prefer to shim the carrier or trans as it would be easier than the rear axle.

Does anyone by chance have the factory angles on a 1500 ECSB 2WD w/ 2 pc. shaft? That would be super helpful.

Thanks

 

You usually want a slightly negative pinion angle so when you really apply power the axle rotates to 0 degrees which is ideal...

 

set the shaft coming from the transmission at the same angle as the output shaft using an adjustable carrier bearing bracket. then youll need to shim your rear end to point the pinion down about 2*. the angle of the 2nd driveshaft isnt that important as long as your u joints are within the operating specs.

 

Some good info. For some reason, I thought a max. of -3° was a reasonable, if not optimal spec. Or was it +3 to -3° was the range? And not to go outside that.

Also, I wonder if it's more critical on a ECSB or a RC, or if the specs vary from one to the other cab configuration?

And yes, I know, no carrier bearing on a RC like on a EC. I meant aside from that. I was also under impression trans sit on a relatively flat plane, no?

Stewy, yours was 1st post I ever remember detailing it. Way to go.

 

This probably won't help you at all, but usually(not always) vibrations that start between 42-45 mph and get worse with higher speeds, are wheel/axle speed related, not prop-shaft speed related. Prop-shaft speed related vibrations start vibrating at a much lower speed, like 5-10 mph.

To try to help answer your driveline/u-joint angle question, is there any chance you could post up a sketch of your setup and angles. Just reading your post, I'm a little confused.

 

I know for a fact its thedriveshaft. Nothing else changed after the 80e swap and no vibration prior to that. My tailshaft on the 80e was leaking due to the vibration. I replaced the entire tailhousing which includes a new bushing as i know those can cause vibes. I also had all the ujoints, carrier bearing and had the driveshaft balanced. So its the driveline angle.



When i get back home i will start working on this.

I drove to chicago today and pulled down 18.8 mpg 65 cruise!!! Holy ****. They must have changed season gas because a couple months ago i could only get 14.2 mpg. I didnt think 18.8 was possible with a cammed 6.0/4l80/4.10s. I wonder how much id gain if i took off these fat 285s off all 4 corners in favor of some factory sized 255s

 

Mike, I didn't realize or I'd forgotten a worn t-shaft bushings could cause a vibe problem, only of its' leaking can be a pain. Good heads up.

Nice MPG. You'd cry if ya knew mine.

And I think mine improved on yesterday's fillup, cause I went a good ways better on 1/2 tank. But I have some issues... for sure.

 

I had a vibration from about 50-85 that I only noticed after I did a ploy trans mount and Caltracs. It turned out that my (steel) driveshaft was bent. My buddy that owns a shop told me it was bent but I didn't believe him. Finally after two weeks of dicking with shims trying to adjust driveline angle I took it out and took it to the driveline shop. Sure enough was correct. They got it straight and banalnced out and it has been good ever since.

 

I'd hope that's not the issue since I've already had it balanced

 

Make sure that you slip yoke fits the tailshaft pretty tight, I ordered a brand new combination u joint and slip yoke from dennys then had the shaft belanced. well bout 6-8 months after got a small vibration that grew and grew, so i swapped the tailshaft housing with bushing, smooth for about a week, done that twice before i noticed my yoke was fucked