Axle shim changed shift feel?

I've been running a 3 degree axle shim for a few months now since I lifted my truck. It points the rear diff more upward and it feels like the truck has been shifting different.

It's always been clunky feeling but now it feels even more clunky between gears and harder to get a smooth shift. I guess the shim is causing more axle wrap?

I have been thinking of just taking the shim out I don't think it helps much of anything. Has anyone had this experience?

 

I recently took out my 3* shim over the summer but can't say I felt any difference in shifting. Between the ujoints on the driveshaft and the trans mounts, etc I don't think it changes anything that would effect the trans/shifter.

 

Yeah, I wouldn't think so either but I swear it feels clunkier now. Like 1st to 2nd was always clunky on my rig but now 2nd to 3rd feels that way too and it was never like that before the shim. Why did you end up taking yours out?

 

Just seeing if it really made a difference. I did not notice a difference in rear end vibes w/ or w/o them.

 

Question for you... does the fat end go towards the back of the truck or the front? I have been told the rear, but for the life of me I cannot visualize the correction on the pinion angle...

 

Yes the fat end points towards the back. Skinny end towards the front of the truck. That's what Toytec told me anyway and based on what I have found on TW.

If the fat end was forward it would point the pinion downward, which wouldn't make sense because your operating angle would be more extreme. It's definitely hard to visualize but I took a before and after picture when I did mine and it's definitely pointing up more now.

 

Putting the fat end toward the rear and the thin end pointing forward toward the front of the truck actually rotates the differential pinion upward.

Conversely, putting the the fat end on the spring perch pointing toward the front of the truck and the smaller tapered end pointing toward the rear of the truck rotates the differential pinion downward.

On mine this is with a moderate lift, no flip of the perch, and the center carrier bearing at the factory height position (no shims).

I tested this directly with 5 different shim sizes and drew a giant image. After I was done measuring all angles I tried to obtain the lowest ujoint operating angles of all three joints (on a 4WD) to minimize their vibration as the angles grow during axle wrap.

So in my case at static, the differential points a bit downward and has greater ujoint angles when it does not matter, but during acceleration/operation the differential then rotates upward and those operating angles then decrease to minimums. Vibes and shudder were eliminated.

But since every lift is different, you must measure angles first.

 

Thank you. Did you ever try the carrier bearing shims? How many degrees of shim did you end up with? Just curious.

 

Yes, and after enormous trial/error attempts I struck out going that route.

What worked best for me was to carefully measure the driveshaft angles, flange angles on both the transmission and pinion of the diff., then determine the to operating angles of the 3 ujoints, and then shim the differential last.

I first got the truck precisely level and measured the drive shafts. Then removed the shafts from the trans/diff flanges and measured them in order to get good angles. Do not use a cheap digital angle gauge.

 

You have been noticing harder shifting since you installed the lift or just the shims ?
Did you go up in tire size ? heavier foot on the gas pedal will also make the trans shift a little more aggressive ?
Subbed for the outcome as I cant say I have heard of this either .

 

It's manual by the way I should have clarified. It didn't do it after the lift, just after the shim. Yeah I have one size bigger tires than stock but it did it before I added them. I wouldnt say it shifts harder, just feels clunkier when I shift. I feel like I have to take extra time and finesse the clutch a little bit just to get a smooth shift.

 

I could see the truck being a little clunky with a manual after shimming .The suspension angle is under load as you are accelerating and then goes to a negative as you release your clutch . When your clutch is pushed to the floor , your rear differential drives the driveshaft as you coast . They call it reverse powerflow . It will take more time for the synchronizers in the transmission to compensate for this effect

Sorry , though you had an automatic

 

Okay I figured it was something like that, that makes a lot of sense. Thank you. I may still take out the shim and drive for a bit to see if it helps without it, cause I miss the way I used to be able to bang through the gears before. It's a regular cab so it has a one piece shaft, the more I've read on here, the more it sounds the shim isn't necessary in my truck with only a 2.5 ish inch lift.