Pinion angles

[747mopar]

I've been trying to track down a high speed vibration in my Charger that's been there from day. Because it runs perfectly until you get over 80 mph hour (mostly after letting up) I've put it off in hopes that the tranny swap with the new shaft would cure it but it persist. I pretty sure I've got it narrowed down to the rearend which is good seeing how I'll be putting together a 489 with 4:10s soon but thought it would be interesting to see what all of you have to say about "Proper pinion angles". I've spoke to the guys at Tremec and done allot of research and almost all say tranny should point slightly down, pinion slightly up and the centerlines for both should be parallel with one another. Mine is within spec but I'll likely shim it to perfection just to totally eliminate the possibility.

 

[bm02tj]

You need to take axle wrap into consideration as well

 

[dvw]

If your going to hammer on it I run about 5 degrees nose down with leaf springs. This is pinion to drive shaft. Your trans to drive shaft will be much less (about 1.5). Under hard acceleration the pinion will rise allowing the joints to run close to each others angles. I run this set-up on the street with no vibration. Car runs 11.0 been like this at least 25 years, never broke a U-joint.
Doug

 

[383man]

Like these guys said you want the eng/trans centerline and the rear pinion centerline the same angle but not the same line when on the throttle. Depending on the rear suspension will determine how much down it needs to be set at rest so they will be on paralell centerlines when on the gas. Ron

 

[Wookie316]

I've been trying to track down a high speed vibration in my Charger that's been there from day. Because it runs perfectly until you get over 80 mph hour (mostly after letting up)
View attachment 250876

Also make sure that your slip yoke is no more then 1" out of the splines in the tranny.
This quote came direct from Denny's Driveshaft.............

"A shaft that has more then the maximum 1" of slip travel may have some sort of vibration or shudder because the slip yoke will not be where it should be and it will become unstable on coast mode operation when the splines are relaxed."

He described my shudder to a "T" ! It was an off load vib for the most part. My car was smooth as glass till 60MPH. It was after that this came into effect.

 

[747mopar]

Also make sure that your slip yoke is no more then 1" out of the splines in the tranny.
This quote came direct from Denny's Driveshaft.............

"A shaft that has more then the maximum 1" of slip travel may have some sort of vibration or shudder because the slip yoke will not be where it should be and it will become unstable on coast mode operation when the splines are relaxed."

He described my shudder to a "T" ! It was an off load vib for the most part. My car was smooth as glass till 60MPH. It was after that this came into effect.

No worries there Wookie, I had a new shaft made and it's set at 1" from bottoming at rest on it's own weight.

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This is what I expected to hear and even asked the Tremec guy about running the pinion lower to compensate for spring wrap but he insisted it wasn't necessary? I guess I'll look into it some more.

 

[benno440]

read up on this a few weeks ago, put a gauge on your rear seal for your tranny, then if

ladder bar: 1* of rearend up
4 link: 2* of rear end up
leafs: 5-7* of rear end up

this is all at ride height with full load

 

[dvw]

read up on this a few weeks ago, put a gauge on your rear seal for your tranny, then if

ladder bar: 1* of rearend up
4 link: 2* of rear end up
leafs: 5-7* of rear end up

this is all at ride height with full load

There are cases where the rear end will point up but only if the motor/trans C/L is tilted down significantly at the rear. Your numbers are close but the nose of the pinion in relationship will be pointing down with stock engine /trans mounting location.
Doug

 

[747mopar]

You took the words right out of my mouth, my motor and tranny are pointed 2.5 degrees down (where it was with the 727) and the pinion up 1 degree so I'm pretty close to the parallel method. Here's my problem or should I say question with putting the pinion so far down, I understand that under hard acceleration the pinion will rise but with a street car the majority of the time it will be in more of a relaxed position meaning it would be running an incorrect angle 90% of the time? For drag racing this makes good sense with slicks and the car being dedicated to hard acceleration it would spend most of it's time with the pinion wrapped up, just thinking out loud.

 

[dink]

Its a sign of weak leaf springs replace them then do the shims ***new u bolts**** a four wheel alignment also make sure the engine and trans mounts are poly helps and aligned...

 

[benno440]

I have been recommended this a few times, hopefully It helps.


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Its a sign of weak leaf springs replace them then do the shims ***new u bolts**** a four wheel alignment also make sure the engine and trans mounts are poly helps and aligned...

everything on his car is new.

 

[747mopar]

Its a sign of weak leaf springs replace them then do the shims ***new u bolts**** a four wheel alignment also make sure the engine and trans mounts are poly helps and aligned...

Everything on this car is new, the suspension is all brand new from front to back including the leaves and u bolts plus the springs have been upgraded to stiffer ones as well.

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Oops didn't see your comment Benno, looks like you covered that.

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I have been recommended this a few times, hopefully It helps.
View attachment 250976

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everything on his car is new.

Thanks for the chart Benno, more food for thought.

 

[dvw]

You took the words right out of my mouth, my motor and tranny are pointed 2.5 degrees down (where it was with the 727) and the pinion up 1 degree so I'm pretty close to the parallel method. Here's my problem or should I say question with putting the pinion so far down, I understand that under hard acceleration the pinion will rise but with a street car the majority of the time it will be in more of a relaxed position meaning it would be running an incorrect angle 90% of the time? For drag racing this makes good sense with slicks and the car being dedicated to hard acceleration it would spend most of it's time with the pinion wrapped up, just thinking out loud.

My street car has been 5 degrees down for 30 years. Runs vibration free at 70 mph even with a 4.30 gear.
Doug

 

[Dennis H]

This is getting complicated. My Tremec was shoved and beaten in - in the driveway by a shade tree mechanic with no consideration of any of this. In 2008. A hack job. No vibration to 113 mph and beyond. Look elsewhere. Good luck.

 

[747mopar]

Thanks guys like I said before in the original post I'm pretty sure it's in the rear end, I'm swapping to a 4:30 so we'll see. I do appreciate the input, at least I feel pretty good about the pinion angle.

 

[Meep-Meep]

I agree the drive line angle needs to be equal (under load or average) at slip yoke and at pinion. Also to comment about the slip yoke end. I have a vibration in the Charger and zeroed in on the excessive tail shaft bushing to slip yoke clearance. I can grab the front U joint and move it up and down 1/16". This only vibrates in a no load situation and during coast, similar to what was described above. So for starters make sure the slip yoke doesn't wiggle much and the engagement is correct.

 

[747mopar]

Thanks Meep, the Viper the tranny came out of had 17,000 miles on it and felt tight but I'll check it again just to be sure.

 

[747mopar]

I agree the drive line angle needs to be equal (under load or average) at slip yoke and at pinion. Also to comment about the slip yoke end. I have a vibration in the Charger and zeroed in on the excessive tail shaft bushing to slip yoke clearance. I can grab the front U joint and move it up and down 1/16". This only vibrates in a no load situation and during coast, similar to what was described above. So for starters make sure the slip yoke doesn't wiggle much and the engagement is correct.

Because the gear change was already on the agenda I tackled that last weak and it still persist:angryfire:. I checked the slip yoke like Meep suggested and let's just say it wiggles allot! With the help from the guys at Don Sharpton Auto (where I bought the tranny) I was able to get a part # and got the bushing and seal kit already so this weekend I'll tackle that.

Not feeling very optimistic.

 

[Meep-Meep]

A loose slip yoke will definitely cause a driveline rumble sound or vibration. Also check the yoke dimension with calipers or a mic to see where the error actually is. The yoke in my Charger is a new 7290 (Spicer 1330 yoke is NLA) but .005" undersize, and with no real way to fix that, I made a new bushing for the tranny. Nice and snug now so hoping for vibration free driving!

 

[cdr]

i just went through all of this & this is what i set my angles ,,trans is 1.5 going down from left to right,shaft is .5 going down L to R,
rear end is 0 not under a load, i also had a nice lite 4 in diam alum shaft built.