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Steve
Steve, Classic Car Owner
Category: Classic Car
Satisfied Customers: 3432
Experience:  Owner of classic cars with knowledge of many older brands. has been my hobby/interest since before I was even driving.
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1987 rear vibration at 58 to 64 mph, the vibration is

Customer Question

1987 rear vibration at 58 to 64 mph, the vibration is intermittent . I balanced the driveshaft, half shafts,new u joints,wheel bearings,tried different wheels and tires. The only difference with the different wheels,
JA: Thanks. Can you give me any more details about your issue?
Customer: The other wheels were wider, and the vibration moved to a higher speed
JA: OK got it. Last thing — Chevy Mechanics generally expect a deposit of about $18 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 9 months ago.
Category: Classic Car
Expert:  Roy Belding replied 9 months ago.

good evening my name is ***** ***** I will assist

what make and model and trans????

Roy

Customer: replied 9 months ago.
4L60E Chevrelot.
Expert:  Roy Belding replied 9 months ago.

electronic trans in an 87??? what model truck??

Roy

Customer: replied 9 months ago.
It's in a*****Rod. It's an LT1 with a 4L60E transmission with 1987 corvette rear end suspension.
Expert:  Roy Belding replied 9 months ago.

wish you would have posted that in your original post. working blind up to this point

what size wheels are you using front and back??

Roy

Customer: replied 9 months ago.
Rims are 16 x 7. Tires are 225/60x16. Out of curiosity, I tried 8-1/2 x 17 wheels with 285/40x17 tires and the vibration went from 58 to 64 mph to 68 and up mph.
Expert:  Roy Belding replied 9 months ago.

did you have the alignment checked to be sure the front and back are square with each other??

the different wheel speeds with different tires and wheels is definitely a contributing factor to this.

Roy

Customer: replied 9 months ago.
it was the first thing I did.
Expert:  Roy Belding replied 9 months ago.

I am not a wheel and tire expert for matching like this but you need to get the right combo to get this resolved. I will opt out to see if anybody else can help

Roy

Customer: replied 9 months ago.
Stop now unless this is covered under my question. I am not authorizing additional charges. Thank you.
Expert:  Steve replied 9 months ago.

You should not get charged any additional if you continue with this question. Any billing inquires should be addressed by customer service, experts are basically sub contractors here.

With that being said your issue sounds like the pinon angle is off. This will cause a vibration and the different size tires changed rotational speed which changes when the vibration comes in. the same thing would happen with a gear ratio change.

This link should take you to a page that will help explain how to set proper pinion angle/driveshaft angle.

http://www.hotrodhotline.com/md/html/drive_shaft_harmonics.php

Customer: replied 9 months ago.
My rear end has fixed differentIal. I have 3 degre down angle on the transmission, and 3 degre up on the rear end. I also put a constant velocity double universal Joynt in the driveshaft. I was told if there was something out of alignment, that this would correct the problem, lt did not.
Expert:  Steve replied 9 months ago.

Did the double u-joint set up change the vibration at all?

Customer: replied 9 months ago.
No.
Expert:  Steve replied 9 months ago.

You said this is intermittent, if you have manual control of the torque converter lock up. Will you get this vibration when the converter is unlocked also?

Driveshaft angle seems to be on the high side but is within reason.

Customer: replied 9 months ago.
If I do have manual control of the torque converter, I don't know how to do it.

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