The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > General Truck Forums > Suspension

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 05-03-2017, 05:35 PM   #1
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
rear end pinion angle issues

I took my 49 gmc on its maiden voyage today to the muffler shop. on the way back i noticed under acceleration the rear end is literally rotating up to 30 degrees from where it is at stopped. needless to say this scared me to death. I will explain what i've done so far below.

1995 s10 frame
3" Belltech lowering leaf springs
1.5" home made set back plates to center the rear tires in the wheel well.
blisten(sp) drop shocks.

i might need pinion angle shim? whatever it is is scary as hell driving it and it starts vibrating pretty violently around 30mph.
Lookin4the1 is offline   Reply With Quote
Old 05-03-2017, 07:44 PM   #2
tinydb84
Registered User
 
tinydb84's Avatar
 
Join Date: Jul 2009
Location: San Jose Ca
Posts: 2,379
Re: rear end pinion angle issues

Is it moving back and forth of just stuck there? Did you weld the perches on?
__________________
David
Used parts build: http://67-72chevytrucks.com/vboard/s...d.php?t=638991

My brother's Nova: http://www.67-72chevytrucks.com/vboa...d.php?t=727985

Instagram: Tinydb84
tinydb84 is offline   Reply With Quote
Old 05-03-2017, 07:56 PM   #3
racecougar
Registered User
 
racecougar's Avatar
 
Join Date: Jan 2013
Location: Imperial, MO
Posts: 794
Re: rear end pinion angle issues

Right, if it's actually rotating back and forth, shims aren't the answer. Are the leaf springs wrapping, is the housing rotating on the tubes, or are the tubes rotating on the spring pads?
__________________
Rod @ AzzKicker Cars
1965 C10 SWB - Build Thread
racecougar is offline   Reply With Quote
Old 05-03-2017, 08:20 PM   #4
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
Re: rear end pinion angle issues

the tubes are rotating on the spring pads. i've got everything bolted down tight. If by chance it is the leaf spring wrapping. i'll have that fixed in a few days. i have a set of cal tracs I'm putting on just to be safe
Lookin4the1 is offline   Reply With Quote
Old 05-03-2017, 08:30 PM   #5
PGSigns
Senior Member
 
PGSigns's Avatar
 
Join Date: Jan 2011
Location: Hayes Va
Posts: 3,237
Re: rear end pinion angle issues

The tubes have to be welded to the spring pads. Also the blocks need to be a bit wider than the spring pads. How much is the rear offset from the locating pin? That can have a effect on the spring.
Jimmy
__________________
60 to 66 Chevy and GMC window decals
http://67-72chevytrucks.com/vboard/s...d.php?t=661131
Good friends, good food and a hotrod what else do you need?
1966 BBW long fleet Daily driver
1965 BBW short fleet Sold and going to a good home
1965 Suburban
2003 3500 Duramax
2005 Ultra Classic
PGSigns is offline   Reply With Quote
Old 05-03-2017, 08:40 PM   #6
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
Re: rear end pinion angle issues

right around 1.25 inches. on the spring pad. i plan to eliminate any chance of spring wrap with these caltracs
Lookin4the1 is offline   Reply With Quote
Old 05-03-2017, 09:15 PM   #7
racecougar
Registered User
 
racecougar's Avatar
 
Join Date: Jan 2013
Location: Imperial, MO
Posts: 794
Re: rear end pinion angle issues

To reiterate: The spring pads must be welded to the tubes.
__________________
Rod @ AzzKicker Cars
1965 C10 SWB - Build Thread
racecougar is offline   Reply With Quote
Old 05-03-2017, 09:16 PM   #8
mongocanfly
Senior Member
 
Join Date: May 2015
Location: alabama
Posts: 2,933
Re: rear end pinion angle issues

Pgsign right..you gotta weld the spring pads to the axle tube..don't rely on bolts to hold it..if its moving that much I'm suprised you havnt broke somethimg yet..30 degrees is pretty drastic..make sure your pinion angle matches your trans angle..usually around 3 degrees
mongocanfly is offline   Reply With Quote
Old 05-04-2017, 12:58 AM   #9
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
Re: rear end pinion angle issues

i apologize for my idiocracy, i'll post an image so you guys can clear it up for me. I think you're telling me to weld A to B in this photo?

Lookin4the1 is offline   Reply With Quote
Old 05-04-2017, 12:59 AM   #10
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
Re: rear end pinion angle issues

the perch is secured to the axle tube because it came stock that way. i have no clue why this thing is rotating now.
Lookin4the1 is offline   Reply With Quote
Old 05-04-2017, 01:09 AM   #11
mongocanfly
Senior Member
 
Join Date: May 2015
Location: alabama
Posts: 2,933
Re: rear end pinion angle issues

The way your post #4 read it sounded different.. in your picture the perch lS welded to the axle tube..that's ok .don't weld a to b ..from what I see there should be no way that differential will rotate 30 degrees as long as the perches (a) is welded to the axle tube..if it would rotate 30 degrees i would think your u-joints would be broke..if it is 30 degrees then you've got a serious problem elsewhere

Last edited by mongocanfly; 05-04-2017 at 01:17 AM.
mongocanfly is offline   Reply With Quote
Old 05-04-2017, 01:15 AM   #12
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
Re: rear end pinion angle issues

yeah i'll do some more investigating but I'm pretty sure i have a serious problem. problem is it only does it when accelerating so its hard to actually see my issue.
Lookin4the1 is offline   Reply With Quote
Old 05-04-2017, 01:21 AM   #13
mongocanfly
Senior Member
 
Join Date: May 2015
Location: alabama
Posts: 2,933
Re: rear end pinion angle issues

Hang a gopro underneath..
mongocanfly is offline   Reply With Quote
Old 05-04-2017, 06:53 AM   #14
PGSigns
Senior Member
 
PGSigns's Avatar
 
Join Date: Jan 2011
Location: Hayes Va
Posts: 3,237
Re: rear end pinion angle issues

Post pictures of your entire setup if you can. We may be able to see something amiss.
Jimmy
__________________
60 to 66 Chevy and GMC window decals
http://67-72chevytrucks.com/vboard/s...d.php?t=661131
Good friends, good food and a hotrod what else do you need?
1966 BBW long fleet Daily driver
1965 BBW short fleet Sold and going to a good home
1965 Suburban
2003 3500 Duramax
2005 Ultra Classic
PGSigns is offline   Reply With Quote
Old 05-04-2017, 07:55 AM   #15
Keith Seymore
Registered User
 
Keith Seymore's Avatar
 
Join Date: May 2009
Location: Motor City
Posts: 6,764
Re: rear end pinion angle issues

The pinion nose of the axle moves up and down quite a bit under acceleration and deceleration, due to leaf spring wind up.

I had an opportunity to drive my '87 pickup without the box on it and was surprised at how much motion there was going on back there.

Assuming that the perches are welded to the tube it could very well be normal.

K
__________________
Chevrolet Flint Assembly
1979-1986
GM Full Size Truck Engineering
1986 - Present
Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926
My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524
Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/
Keith Seymore is offline   Reply With Quote
Old 05-04-2017, 01:43 PM   #16
mongocanfly
Senior Member
 
Join Date: May 2015
Location: alabama
Posts: 2,933
Re: rear end pinion angle issues

This is just a thought..keith is right that there's a lot of movement in the rear..but..does your driveshaft have a slip joint in it? If so do you have the u-joints in time? If not it will shake your teeth out..also, check for bad u-joints
mongocanfly is offline   Reply With Quote
Old 05-04-2017, 10:55 PM   #17
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
Re: rear end pinion angle issues

drive shaft is all new, it is 2 piece from the s10. all the joints are new. i'm not near the truck it will be next week before i can post a few pictures of the entire setup.
Lookin4the1 is offline   Reply With Quote
Old 05-05-2017, 12:26 AM   #18
mongocanfly
Senior Member
 
Join Date: May 2015
Location: alabama
Posts: 2,933
Re: rear end pinion angle issues

Won't matter if its all new or not if it isn't timed correctly...get a good pic of the entire driveshaft...are you familiar with u- joint timing?
mongocanfly is offline   Reply With Quote
Old 05-05-2017, 12:34 AM   #19
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
Re: rear end pinion angle issues

no I'm not familiar with U-joint timing
Lookin4the1 is offline   Reply With Quote
Old 05-05-2017, 12:44 AM   #20
mongocanfly
Senior Member
 
Join Date: May 2015
Location: alabama
Posts: 2,933
Re: rear end pinion angle issues

The yokes on your driveshaft need to be lined up..here's a video about u joints that explains a lot..https://m.youtube.com/watch?v=gmV4qwLfOMY
mongocanfly is offline   Reply With Quote
Old 05-05-2017, 12:49 AM   #21
mongocanfly
Senior Member
 
Join Date: May 2015
Location: alabama
Posts: 2,933
Re: rear end pinion angle issues

Maybe this'll help explain as well...
Attached Images
 
mongocanfly is offline   Reply With Quote
Old 05-07-2017, 10:39 PM   #22
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
Re: rear end pinion angle issues

Lookin4the1 is offline   Reply With Quote
Old 05-07-2017, 10:39 PM   #23
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
Re: rear end pinion angle issues

i'll try to phase the U joints on tuesday and take better pictures.
Lookin4the1 is offline   Reply With Quote
Old 05-07-2017, 10:43 PM   #24
Lookin4the1
Registered User
 
Join Date: Dec 2015
Location: Anderson, SC
Posts: 63
Re: rear end pinion angle issues

Lookin4the1 is offline   Reply With Quote
Old 05-07-2017, 10:47 PM   #25
mongocanfly
Senior Member
 
Join Date: May 2015
Location: alabama
Posts: 2,933
Re: rear end pinion angle issues

Were the u joints outta phase?
mongocanfly is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 06:36 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 1997-2013 67-72chevytrucks.com