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-   -   Pinion offset? (http://www.hotrodders.com/forum/pinion-offset-231672.html)

fasteddy_1947 04-09-2013 06:58 PM

Pinion offset?
 
Ran into one today that is blowing my mind. Got my driveshaft bolted in and it didn't look quite perpendicular to the rear end. Kind of looked like an angle tween the differential pinion shaft and the transmission output shaft. So did some measuring cause I obviously mismeasured when I made my transmission mount. So, unbolted everything forward of the rear end (1998 Camaro posi) and slid it over to where it all looked perpendicular (90 deg). This moved my eng and trans over to where it is two inches closer to the right frame rail thean the left. That can't be right ! conclusion is that the pinion shaft on rear end is not dead center, although it appears to be. I am measuring something rong here. :pain:What have I forgotten here? I thought maybe leaf spring backwards or something, but they all measure out ok and the center pins are ok and centered but seems that the Camaro pinion shaft is not centered and when squaring everything out to "square" it translates to moving engine and transmission over. Sorry for long explanation, but it has me baffled. Always thought that the front and rear universals and driveshaft were dead center on all cars. Is that what I get for thinking all by myself again? What have I missed here? Thank you, in advance, for any help on this. trans is th700 chevy behind 94 350, rear end again is 98 camaro. all in 39 chev coupe chassis. Thank you !

Actionjk 04-09-2013 07:23 PM

I do rears for a living,almost all your rears are offset,most Chevys,1",most 9" Fords 2 1/2",some as much as 4",if you read up on driveshaft angles,you"ll find,if you line a driveshaft up perfectly,vertically,and horizontally,it will most likely vibrate,the offset on your Chevy rear is fine,make sure you have about 2 deg. difference between,trans./driveshaft and driveshaft/rear end,(up and down)and it will run smooth if everything else is good.

sedanbob 04-09-2013 07:56 PM

Side to side offset is just like vertical offset - you want some, and you want the angles at each end to be opposite. As long as your rear axle and transmission output shaft are perpendicular, you'll be fine.

fasteddy_1947 04-09-2013 09:02 PM

Actionjk and sedanbob, thank you for the information. Wow thought I had a real problem here and getting ready to fire up the torch to fix it. One thing I learn over again every day is: There is a whole lot more that I don't know than I do. Made my day, Thank you again. Been a great day till then, now still great day and learned something new. And got driveshaft fitted and pwr steering installed. Things coming together. Haven't yet tried figure the vertical angles on d/s as still have body off and only weight is in front. What's best (easiest) way to measure those angles? Someone mentioned laser pointer, but don't know how to do that.

sedanbob 04-09-2013 10:22 PM

Easiest is probably a magnetic angle finder - cheap and available at most hardware stores. Rotate the rear until the yoke is vertical to measure that end, and the end of the output shaft on the transmission.

big gear head 04-10-2013 06:14 AM

All of the 12 bolt, 8.2, 8.5 and 7.5 Chevy car rear ends that I know of have the pinion offset 1/2 inch to the right. This makes the pinion 1 inch closer to the right side than the left.

lmsport 04-10-2013 06:39 AM

Most all GM c-clip rears have the same length axle in both sides, meaning the diff cross pin is what is centered in the car.

fasteddy_1947 04-10-2013 09:11 AM

Like I said before: each day is a reminder to me that what I know is nothing compared to what I don't. I appreciate the help. Can put it all back together now and tighten everything up. Will have to see what can find to figure the D/S angles, but doesn't sound that hard and have looked over what has been posted here on what to look for. I thank you all for the help on this and it has really taken a load off.

Cape Cod Bob 04-10-2013 07:55 PM

Quote:

Originally Posted by fasteddy_1947 (Post 1664889)
Like I said before: each day is a reminder to me that what I know is nothing compared to what I don't. I appreciate the help. Can put it all back together now and tighten everything up. Will have to see what can find to figure the D/S angles, but doesn't sound that hard and have looked over what has been posted here on what to look for. I thank you all for the help on this and it has really taken a load off.

Yes, put it together and tighten up. Don't weld the spring to axel brackets yet. Wait till all the weight is on then check the pinion angles. The driveshaft should be the last thing you make before getting on the road. IMHO :welcome:

fasteddy_1947 04-10-2013 10:04 PM

Yes, I've read that here before. Going to be awhile before ready for that though. Extensive body work next, lots of rust (or holes, where there was rust before sandblasted body, kinda like Swiss cheeze). Was lucky with the frame as it pretty solid all way around. Thank you for heads up reminder on that.

evolvo 04-10-2013 10:17 PM

http://www2.dana.com/pdf/J3311-1-DSSP.pdf

http://www.iedls.com/asp/admin/getFi...&TID=28&FN=PDF

A little lite reading:D

fasteddy_1947 04-16-2013 06:36 PM

Just finished the 'light reading' you sent along. Takes a lot of the guess-work, and hope I aint really screwing this up-work out of the mix. Thank you for taking the time to send it along. :D


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