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Re: Weird vibration just backing off throttle [Re: Publicbottle] #1657357 08/13/14 06:36 PM 08/13/14 06:36 PM
Joined: Aug 2003 Posts: 43,352 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,352 Bend,OR USA	I would remove the spring perches and then shoot for 5 to 7 degrees nose down(from 90 degrres from the ground, IE 85 to 83 degrees nose down) on the pinion shaft Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Weird vibration just backing off throttle [Re: Publicbottle] #1657358 08/13/14 07:47 PM 08/13/14 07:47 PM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Actually the ground really don't matter. You need to put the angle finder on the end of the trans output shaft to find it's angle and you want your rear pinion parallel with the trans output shaft angle under a load or as close as you can get. So a few degrees down from that point would be my suggestion. Does that make sense?

Re: Weird vibration just backing off throttle [Re: Challenger 1] #1657359 08/14/14 06:25 AM 08/14/14 06:25 AM
Joined: Dec 2005 Posts: 885 alberta Publicbottle OP super stock
Publicbottle OP super stock Joined: Dec 2005 Posts: 885 alberta	Yes this is beginning to make sense. Thank you very much for helping with this! So just for the record....these old mopars are typically a trans "up" and rear pinion "down" configuration? Would it be worth trying to get my trans output angle to be in the positive?? ( up? )

Re: Weird vibration just backing off throttle [Re: Publicbottle] #1657360 08/14/14 11:37 AM 08/14/14 11:37 AM
Joined: Feb 2003 Posts: 16,167 Mesa, Arizona D dart4forte I Live Here
dart4forte I Live Here D Joined: Feb 2003 Posts: 16,167 Mesa, Arizona	Do you have the Mopar chassis book?

Re: Weird vibration just backing off throttle [Re: dart4forte] #1657361 08/14/14 12:03 PM 08/14/14 12:03 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	If the front yoke/shaft interface angle is a "V" then you want the pinion/shaft interface angle on the other end to be a "^" (an upside down "V" and you want several degrees of angle on each end & the angles to be equal. The factory angles you have in place will dictate which "V" is up and which "V" is down. You just dont want either/both ends in a perfect straight line and you dont want too much angle but you do need some angle (several degrees) plus you need a bit more downward drop on the pinion cuz it rises (how much I ain't sure/check on that/depends on your app, drag/street etc). A record setting drag racer might want a straight line for the nth degree of no horsepower loss (angles cost power however slight) but for everyone else a slight angle is needed as ujoints will wear excessively if the angle is dead on straight (you'd think it'd be the opposite but it ain't), something about the needle bearings need to circulate/move iirc ?? live every 24 hour block of time like it's your last day on earth

Re: Weird vibration just backing off throttle [Re: dart4forte] #1657362 08/14/14 12:19 PM 08/14/14 12:19 PM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Quote: Do you have the Mopar chassis book? I know you weren't talking to me, but yes I do. And I have read the crap out of it over the years, long before I was a drag racer.

Re: Weird vibration just backing off throttle [Re: Challenger 1] #1657363 08/14/14 12:33 PM 08/14/14 12:33 PM
Joined: Sep 2011 Posts: 2,042 colorado S savoy64 top fuel
savoy64 top fuel S Joined: Sep 2011 Posts: 2,042 colorado	the only pinion angles that go down are on race cars--that is hopefully going to be at 0 degrees at full throttle so you have less power loss ----if you have a driving around everyday car the angles should be close to matching in a parallel universe---tranny shaft at -3 degrees the pinion should be at +3 degrees---they should be close to matching---this lets the u joints break and all those little needle bearings get to go around in a circle and feel good about themselves....just google it and you will see----dont try gomering it...

Re: Weird vibration just backing off throttle [Re: savoy64] #1657364 08/14/14 03:24 PM 08/14/14 03:24 PM
Joined: Aug 2003 Posts: 43,352 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,352 Bend,OR USA	Quote: the only pinion angles that go down are on race cars--that is hopefully going to be at 0 degrees at full throttle so you have less power loss ----if you have a driving around everyday car the angles should be close to matching in a parallel universe---tranny shaft at -3 degrees the pinion should be at +3 degrees---they should be close to matching---this lets the u joints break and all those little needle bearings get to go around in a circle and feel good about themselves....just google it and you will see----dont try gomering it... Automotive U joints need a difference in angles for the needle bearings to rotate to stop them from brinelling(SP?) and killing themsleves from non rotation. It doesn't matter where the difference in angles are, left, right up or down If thier wasn't a diffence in angles on the driveshaft you wouldn't need a U joint, a straight solid shafts would work fine Just like top fuel and funny cars, boats and other with no suspension movement As far as V in the driveshaft angles and misalignment compensation keeping the pinion down in relation to the driveshaft works way better than having the V at the driveshaft and pinion yoke up to start with Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Weird vibration just backing off throttle [Re: Cab_Burge] #1657365 08/14/14 04:52 PM 08/14/14 04:52 PM
Joined: Sep 2011 Posts: 2,042 colorado S savoy64 top fuel
savoy64 top fuel S Joined: Sep 2011 Posts: 2,042 colorado	the angles should be at least 1 degree or more---smaller ujoints maybe 3 degrees----i strongly suggest you google---transmission pinion angle--- and read for yourself---- the 8 degrees up on the pinion would seem too much.....

Re: Weird vibration just backing off throttle [Re: savoy64] #1657366 08/20/14 03:11 AM 08/20/14 03:11 AM
Joined: Dec 2005 Posts: 885 alberta Publicbottle OP super stock
Publicbottle OP super stock Joined: Dec 2005 Posts: 885 alberta	Would just like to post a resolve to my issue. I know I hate reading through a post only to find no solution in the end. Hoping that someone else can learn from my mistakes, I find this a bit embarassing, but glad I got it figured out, a HUGE thanks to Dr. Diff! A great guy and wealth of knowledge!!! Turns out I installed my 3 degree shim in backwards and ended up with over 10 degree negative pinion angle. By reversing the shim (thin end forward) I changed my angle 6 degrees yielding me with a 4.5ish negative pinion angle. Test drive went great and immediately it felt smoother! Thanks everyone!!

Re: Weird vibration just backing off throttle [Re: Publicbottle] #1657367 08/20/14 08:42 AM 08/20/14 08:42 AM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Quote: Would just like to post a resolve to my issue. I know I hate reading through a post only to find no solution in the end. Hoping that someone else can learn from my mistakes, I find this a bit embarassing, but glad I got it figured out, a HUGE thanks to Dr. Diff! A great guy and wealth of knowledge!!! Turns out I installed my 3 degree shim in backwards and ended up with over 10 degree negative pinion angle. By reversing the shim (thin end forward) I changed my angle 6 degrees yielding me with a 4.5ish negative pinion angle. Test drive went great and immediately it felt smoother! Thanks everyone!! Cool deal, IMO the shims should only be left in there for a short time. They make for weak rear end because they will corroad and fall out. Then you have a bigger problem. Get the saddles on the rear end re-welded where there supposed to be.

Re: Weird vibration just backing off throttle [Re: Challenger 1] #1657368 08/20/14 02:05 PM 08/20/14 02:05 PM
Joined: Aug 2003 Posts: 43,352 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,352 Bend,OR USA	Quote: Quote: Would just like to post a resolve to my issue. I know I hate reading through a post only to find no solution in the end. Hoping that someone else can learn from my mistakes, I find this a bit embarassing, but glad I got it figured out, a HUGE thanks to Dr. Diff! A great guy and wealth of knowledge!!! Turns out I installed my 3 degree shim in backwards and ended up with over 10 degree negative pinion angle. By reversing the shim (thin end forward) I changed my angle 6 degrees yielding me with a 4.5ish negative pinion angle. Test drive went great and immediately it felt smoother! Thanks everyone!! Cool deal, IMO the shims should only be left in there for a short time. They make for weak rear end because they will corroad and fall out. Then you have a bigger problem. Get the saddles on the rear end re-welded where there supposed to be. Position the perches where you want the difference in the driveshaft and the pinion shaft and weld them rascal on Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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