Driveline angle

[jeff351]

Can someone measure the angle off the rear of the transfer case for me?

I'm installing an 8.25 axle with a small lift via shackle flip, and need to set the pinion angle. My driveline isnt installed yet. 

[Pete M]

you can measure the angle of the t-case shaft end vertical surface and then compare against the angle of the axle pinion vertical surface.   

[OldSch88L]

Like Pete said.... Basically, if you have a slip yoke driveshaft, you want your pinion to be parallel with your t-case output shaft. Inversely, if you have a telescopic fixed-yoke driveshaft with a double cardan joint, you want your pinion pointing at the t-case output shaft. So due to different factors, measurements off my truck might not be the same as yours, and you're better off measuring by yourself.

[jeff351]

My engine/trans isnt installed yet so was hoping to set the pinion angle before I do all that.

No worries..I'll just wait and weld it up after I get it all put back together. 

[ghetdjc320]

This article gives a thorough explanation and includes videos and pics for reference. May be really helpful moving forward 
 

https://4xshaft.com/blogs/general-tech-info-articles/driveshaft-angles

[gogmorgo]

Keep in mind it's usually advised to put your "parallel" pinion 1-2° below parallel to account for pinion climb under torque. And it's very unlikely you'll find yourself in the position with your setup, but avoid setting your ujoint angles at 0°. It'll take out the ujoints in short order if the bearings aren't rolling around under torque.

[OldSch88L]

On 9/18/2023 at 8:23 PM, gogmorgo said:

Keep in mind it's usually advised to put your "parallel" pinion 1-2° below parallel to account for pinion climb under torque. And it's very unlikely you'll find yourself in the position with your setup, but avoid setting your ujoint angles at 0°. It'll take out the ujoints in short order if the bearings aren't rolling around under torque.

Do you mean the pinion 1-2 degrees downwards compared to the transfer case? With my previous lift, I went with shims that were dead on. It was ok on accelleration and cruising speeds, but got weird noises when I let off around 60MPH... I was having doubts about my backlash settings, but all was within specs at the time, and the diff was quiet otherwise, so I was getting confused... Your comment couldn't come at a better time, as I now have to take measurements again for my new lift, I.E. bad angles, and slight slip yoke wobble due to to over-extension.

[ghetdjc320]

1 hour ago, OldSch88L said:

Do you mean the pinion 1-2 degrees downwards compared to the transfer case? With my previous lift, I went with shims that were dead on. It was ok on accelleration and cruising speeds, but got weird noises when I let off around 60MPH... I was having doubts about my backlash settings, but all was within specs at the time, and the diff was quiet otherwise, so I was getting confused... Your comment couldn't come at a better time, as I now have to take measurements again for my new lift, I.E. bad angles, and slight slip yoke wobble due to to over-extension.

1-2* below the ideal angle for your pinion depending on your setup. See the article posted above for reference on the ideal angle based on the type of driveshaft you’re running

[gogmorgo]

3 hours ago, OldSch88L said:

Do you mean the pinion 1-2 degrees downwards compared to the transfer case? With my previous lift, I went with shims that were dead on. It was ok on accelleration and cruising speeds, but got weird noises when I let off around 60MPH... I was having doubts about my backlash settings, but all was within specs at the time, and the diff was quiet otherwise, so I was getting confused... Your comment couldn't come at a better time, as I now have to take measurements again for my new lift, I.E. bad angles, and slight slip yoke wobble due to to over-extension.

Yeah, slightly below where you would ideally have it set. It's a Newton's third law, equal and opposite reactions thing. When you put significant torque into the rear tires, the axle tries to spin the opposite direction. This is the same lifting force that picks up the front end of drag racers, just not as extreme. There's always going to be a little compliance in the leaf springs, bushings, control arm bushings on a linked axle, so setting the pinion slightly low means you'll have proper alignment under load. In most cases when you're driving you'll be under some load, cruising at a steady speed for example you're usually pushing into the wind.

 

In your case, looking at noises after lifting off the throttle, I'd suspect a different issue. Under liftoff and presumably engine braking if coasting in gear, you're pushing the other direction, so if anything skipping the slight pinion drop and putting it higher would make deceleration in gear better.

Backlash issues would generally either manifest as a clunk when going between off and on throttle, or else a rapid unscheduled and irreversible disassembly of the rear axle, usually not long after install. So I doubt that's your issue.

It's normal to get a little flutter in the exhaust on engine braking, which could rattle the pipe around a bit.

Pinion bearings could make noise under decel. They would also theoretically make noise under acceleration as well but it could be drowned out by the exhaust note I guess. Usually accompanied by a pinion seal leak. Carrier bearings could also make noise, but again they would usually make more noise accelerating. Wheel bearings? Honestly it's real tough to correctly diagnose a noise over the internet.