PINION ANGLE

[747mopar]

The engine is a 413 max wedge. My dad just had it built. Our engine builder ran it on the dyno several times. The trany was just rebuilt also. I will take the time today & pull the drive shaft. I will let you guys know. I will also measure the between the rear & trany again. Loaded & unloaded

Again if it's vibrating sitting still don't waste your time pulling a driveshaft or looking at the pinion angle because they have to be spinning and typically pretty fast to cause a vibration.

Watch the motor at idle, look for movement, look for something that could be hitting then double check the timing, plug wire order, carburation etc to make sure it's not a tuning issue. When you eliminate the simple stuff start double checking the flexplate, torque converter and harmonic balancer.

 

[Bruzilla]

I installed an 8.75 rear from an E body on my 74 Roadrunner. I moved the perches out .75" but at the same angle as the E body's perches were at, and there was a pretty big difference in pinion angles.

And like others, when I had the 8.25 rear in, which had a pinion angle issue, I would only feel a vibration when I came off the gas.

 

[khryslerkid]

Also don't rule out having a miss from crossed plug wires or a bad plug ect that mimics a vibration. Seen this many times.

 

[XMAN JR]

The engine & trans are all newly rebuilt. The engine runs smooth at any rpms. I don't have a lot of time today but I did take the time to take the drive shaft out. Started it up & no vibration at low or higher rpms.

 

[66chargerpat]

This is just a guess, try putting jackstands under the spring perches so the load is on the springs, not the 3rd member. Pat

 

[747mopar]

The engine & trans are all newly rebuilt. The engine runs smooth at any rpms. I don't have a lot of time today but I did take the time to take the drive shaft out. Started it up & no vibration at low or higher rpms.

So it doesn't vibrate with the shaft out but vibrates while sitting still with it in. My first guess is the driveshaft is to long, if it's bottomed out in the tranny it would transfer vibrations to the rear? Put it back in the car then with it sitting on it's tires mark how far into the tranny it goes, Jack it back up and unbolt the shaft and see if it has any play beyond your mark... Should tell you if it's bottomed out.

 

[khryslerkid]

What's the history on the trunnion joint. Has it been rebuilt recently? I know it was on a balance machine but I was just wondering how it might have been included in the balancing procedure.

I know if the pin is off center just a little that it will throw it out of balance. If one of the shims under the bearings were left out, if the bearings or pin is worn out, if aftermarket boot clamps are used and they aren't staggered, if there is a aftermarket boot being used and it's flopping around, if the flange isn't seated properly into the tailshaft flange when tightened.(That's a pretty snug fit) All of these things can cause the trunnion type joint to throw the balance off.

How's the tailshaft bushing, any up and down or sideways play?

If all of these check out then checking your pinion angle would be the next step.

 

[XMAN JR]

What's the history on the trunnion joint. Has it been rebuilt recently? I know it was on a balance machine but I was just wondering how it might have been included in the balancing procedure.

I know if the pin is off center just a little that it will throw it out of balance. If one of the shims under the bearings were left out, if the bearings or pin is worn out, if aftermarket boot clamps are used and they aren't staggered, if there is a aftermarket boot being used and it's flopping around, if the flange isn't seated properly into the tailshaft flange when tightened.(That's a pretty snug fit) All of these things can cause the trunnion type joint to throw the balance off.

How's the tailshaft bushing, any up and down or sideways play?

If all of these check out then checking your pinion angle would be the next step.
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First can you buy a rebuild kit for the trunnion joint ? When the shaft was in the car I checked & rechecked every bolt & nut. The rear u joint is new & tight. My dad bought a new boot from Kramer from PA. The weights they put on it to balance it are all in the back of the shaft. 2 washers about the size of quarters. I put the new boot on before I got it balanced.

 

[khryslerkid]

First can you buy a rebuild kit for the trunnion joint ? When the shaft was in the car I checked & rechecked every bolt & nut. The rear u joint is new & tight. My dad bought a new boot from Kramer from PA. The weights they put on it to balance it are all in the back of the shaft. 2 washers about the size of quarters. I put the new boot on before I got it balanced.

There are some rebuild kits out there. Mainly on ebay. If it's in good shape I wouldn't rebuild it. The cross pin would need to be pressed out if it's worn and the new one has to be pressed back in perfectly centered. Mine was original and showed no wear at all, so I just regreased and replaced the boot. Also they don't recommend a lot of grease in one. Only like 4 ounces. Directions state about a 1/2" on the cover plate, take half of that behind the cross pin and the rest in front of it before attaching the cover plate. (No grease inside the boot)

Is the location of the cross pin centered in the travel of the driveshaft when installed. Not jammed foward as to cause binding? Same thing as if you had a newer style slip joint, not wanting it to bottom out in the tailshaft.

 

[bm02tj]

This does not have the ujoint angles cancelling each other so the rear needs about a 2 deg drop to cover windup
the car it came from would have had more angle because it had a front ujoint

 

[XMAN JR]

Had a little time this morning. The drive shaft is 54 1/4 With rear end on jack stands (loaded) the measurement is 55 3/16 With the rear of the car on jack stands / on the frame rear end (unloaded) the measurement is 54 7/8 With the trunnion type drive shaft I don't know any measurements. Is my drive shaft to short to long.

 

[khryslerkid]

Had a little time this morning. The drive shaft is 54 1/4 With rear end on jack stands (loaded) the measurement is 55 3/16 With the rear of the car on jack stands / on the frame rear end (unloaded) the measurement is 54 7/8 With the trunnion type drive shaft I don't know any measurements. Is my drive shaft to short to long.

If I had mine up on stands I'd get you some measurements. Maybe if you took the u joint off at the rear and push the shaft toward the front and see how much travel you have. Do this with the weight of the car on the rear axle housing.

Can you turn a rear wheel, with the trans in neutral and see or feel any binding as the joints rotate? Otherwise get a guage to check your angles.

 

[khryslerkid]

This does not have the ujoint angles cancelling each other so the rear needs about a 2 deg drop to cover windup
the car it came from would have had more angle because it had a front ujoint

I would think that the trunnion joint acts the same as a regular u joint. Their range of motion should be the same. They could be more sensitive to angle changes? Jmo

 

[TheCoronetKid]

Working on my dads 62 polara & I noticed a vibration when I would start it. So I took the drive shaft & got it balanced. The guy said it was out but not that bad. I put it back in & the vibration is still there. I checked every thing. The rear that's in the 62 is out of my dads 67 gtx. We drove the gtx & it ran fine no vibration. Now a friend of mine says it has to be the pinion angle. Why would the pinion angle change from one car to another ?

So, my question is about what you say...... "I noticed a vibration when I WOULD START IT".... if "when you start it", that would have nothing to do with the drivetrain at all ! So, unless you worded that sentence incorrectly, you have a balance problem in the engine

 

[XMAN JR]

So, my question is about what you say...... "I noticed a vibration when I WOULD START IT".... if "when you start it", that would have nothing to do with the drivetrain at all ! So, unless you worded that sentence incorrectly, you have a balance problem in the engine

Yea I probably didn't word it right. LOL With the car on jack stands & I start it in neutral its ok when I put it in gear it vibrates. When I start it with out the drive shaft & in gear no vibration. Im starting to think my shaft is to short

 

[XMAN JR]

I would think that the trunnion joint acts the same as a regular u joint. Their range of motion should be the same. They could be more sensitive to angle changes? Jmo

I am going to buy a longer shaft. The one im buying is just about 2 inches longer. I Noticed that when I put my shaft in I bolt it to the trany & I have to pull it back a little over an inch to get the u joint into the yoke.

 

[khryslerkid]

Im starting to think my shaft is to short

Story of my life!

 

[XMAN JR]

Story of my life!

LOL I hear ya

 

[khryslerkid]

LOL I hear ya

I can get you a measurement if you really need one. I'll have to jack mine up to do it but I'll do it. Just say so.

 

[XMAN JR]

I can get you a measurement if you really need one. I'll have to jack mine up to do it but I'll do it. Just say so.

That would be great. Then ill feel more confident about my shaft length. I thank you