New posi

I just installed a new chunk with a posi unit and 3.55 gears and I know have a bad vibration. I also put new u-joints in. Vibration is worst around 45 when I back off the gas. Do you think my drive shaft needs balanced. What else could cause this. Thanks.

 

Take the drive shaft out and rotate it 180 deg and re-install.Also check the yoke on your new chunk.Be certain it is the same length as the old one (there are 2 types for our cars)If its the yoke...the drive shaft isnt seated in the trans properly due to different length.Good luck!!

 

Also check that the u-joints are sitting in the yokes evenly. I swapped chunks in my 71 F100 once and had a bad vibration. The rear yoke have a burr on it causing the rear u-joint to be just slightly off center.
Do you hear any gear whine or roaring during any time?
I would take a look at the U-Joints closely.
clint

 

I'm guessing different yoke.

 

Another idea is "Did you overtighten the u-joint bolts?"

I have made the mistake before. If you have overtightened them, and it has started roaring, you must start over with a new u-joint.

 

Did you have the viberation before you change the center section ????

If not then the center section is bad bearing in on the pinion ... Jay

 

No whine or roaring. and no I didnt have a vibration before. It feels like its more near the tranny than the unit its self. I replaced the wheel bearing also. I will have to put it back on the lift thursday.

 

if you had 3.0s or 2.73s before then this vibrations could have been there before. it just would have been at a higher speed. check the condition of the yoke where the u-joint caps sit. look for evidence of wear in the tabs that keep the u-joint caps centered in the yoke. the u bolts should only be tightened to 15 ft/lbs. use blue loctite on the ubolt nuts. check the condition of the trans mount. they are know to go bad and change the angle of engine/trans so the u-joints operate out of phase causing vibration.

 

lot's of drive line shops will see if it needs to be balanced FOR FREE

 

were did you buy your new center ???

 

I bought this one off of ebay. I dont really think its the chunk its self.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=260467697087&viewitem=&sspagename=STRK%3AMEWNX%3AIT

 

he is a good friend of mine that you bought this from and said you should put the back up on jack stand so you can put in gear and run it will till you were it is ,,if you need any help he said feel free to call him anytime he is a wealth of info been doing that for 25 years

 

I am going to put it on the lift thursday and see whats up. I will call him if I cant figure it out. Thanks for the suggestions guys.

 

I s this the radiator you are using? I think im going to get one.

http://www.championcooling.com/1970-77%20maverick/maverick_339aa.html

 

That makes a lot of sense as far as the RPM's with the new ratio goes.
That is also what I was trying to get across as far as the tabs being in good shape. That is what happened to me once. Had a burr on the side of one tab and it forced the u-joint out of center causing a vibration
clint