Another pinion angle ?

-

MoparMcK

Well-Known Member
Joined
May 17, 2015
Messages
297
Reaction score
82
Location
Canton, SD
What is a good pinion angle for my setup? This winter I have been pugging away at relocating the springs and mini tubbing the car. The car is street driven but does hit the track at least 5/6 times a year. Specs are listed below.

72 Demon with a mild 440 4 speed 8 3/4 3.91
Subframe connectors
SS springs 002/003 relocated
Comp engineering shocks

Not that it matters but best ET to date is a 13.07@103. That was before the frame connectors and had stock springs and location. Hoping and have been told, these current mods will make a huge difference. Fingers crossed.

Thanks for any info!
 
I believe the Mopar chassis book says 5-7* down.

Are you using the pinion snubber? Also what tire?
 
I believe the Mopar chassis book says 5-7* down.

Are you using the pinion snubber? Also what tire?


I don't think I will be using the snubber. Found that is a "to each their own" topic.
Tire on the street is up in the air yet but is looking to be a 325/50/15. At the track will be a 275/60/15 Nitto DR.
 
I usually set up leaf spring cars with 6 degrees of negative angle. Seems to work well. If you use bars like a Cal Trac or similar to limit axle rotation you could use a couple degrees less pinion angle.
 
If you are changing from 375-50 to 275-60 this will change the pinion angle . Too much angle up or down will bind the u-joint and cause premature wear or failure . Also , the ride height must be set before the pinion angle must be set . Changing ride height (or tire size ) changes pinion angle . Set that first and then measure the pinion angle . FYI pinion snubbers work , no good on the street , though .
 
Just set it at 3 degrees down and let it go.
PLUS, can you get that 4-5 degrees on the trans to drive line to match?
SS springs don't need 4-5 and the only reason you might need that much is at the track.
The rest of the time your U joint will be twisting way more than it needs, and very likely will cause a cruising vibration.

BTW, without a snubber I was snapping shock eyelets off and with the snubber 1.5 inches from the body it doesn't do that any more.
Here again though, you have SS springs which don't wrap as much.
 
If you are changing from 375-50 to 275-60 this will change the pinion angle . Too much angle up or down will bind the u-joint and cause premature wear or failure . Also , the ride height must be set before the pinion angle must be set . Changing ride height (or tire size ) changes pinion angle . Set that first and then measure the pinion angle . FYI pinion snubbers work , no good on the street , though .


I think you may have misread the tire size. 325/50 and 275/60 is what I plan to run. Only major difference is the width. The car will be sitting on the ground to get everything set.
 
I just read through my "new" Chassis book and have concluded that on that subject, whoever wrote that totally screwed up. They barely mention the crank/ transmission centerline, which is what it's all about. The best way to deal with pinion is to take the driveshaft out and set it aside. Measure the crank/ transmission centerline and use THAT as your reference. If the transmission needs to be changed in relation to the car "level" then change it and measure the centerline again. That shaft and the pinion is all that driveshaft "knows" and the the trans and pinion need to be parallel under full power. "Exactly inline" in other words the three of them forming a straight line is not good either

The whole reason you are pointing it down is so that when the power comes on the thing rotates up under power, and "comes into" parallel
 
I usually do 5* difference. If the trans tail shaft is 0, then pinion is -5* down. If up 1* at trans, then down-4 at pinion. If down 1*at trans, then down-6 at pinion. Kim
 
It's really a crap shoot.

I set my pinion at -4. My trans sits at dam near zero.

Tire affects the twist, rear gear affects the twist, springs affect the twist, track prep or the road your on affect the twist. Slapper bars, cal tracks affect the twist, how you drive normal VS hard launches affect your decision.

I run DOT drag radials with 4.88 rear gear on the street and that's where my car lives so I'm not dead hooking most times.

-4 is working good for my car.
 
Thanks for all the info. I tell you what, there are quite a few different opinions on how to figure this. I have been reading, listening, watching videos, and asking questions for the last couple days to make sure i get this right. The more I do any of that the more confusing it can get.

Some links say to find parallel and measure your angles from there. Mine is +1 on the transand -2 on the pinion. Which then says to get a total of -6 I need to lower my pinion to -7 to achieve 0 under load. If I am understanding correctly. Only one other guy here locally has told me to do i that way. He street races his Nitrous SB Dart and it works.

A couple others state to connect the driveshaft. Measure pinion angle and the rearest point of the driveshaft angle. Add those two together and that is your PA. I.E. PA is -3 and shaft is -3 = -6 total PA. They don't even account for the transmission. Two websites and one local person did this. Person has a 500" BB 727 D60 with 4.30 running low to mid 10s. Proven setup. Its been a few years since he set his up and did say he wasn't a 100% if thats how he did it. So.....

One has told me nothing else matters. Just drop the pinion down to -6 to -7 and run it. He has ran his car this way for 20 years on the street and the track. Small block power auto and runs consistent as hell. Maybe since he is 57 years old it is his old school nature. He has been around the block and had to learn without the resources that I am able to use. Like you guys.

So after all my chatter here and reading what oldkimmer and cope said in detail and basically the exact same way. I think that is how I will figure mine up.

I APPRECIATE EVERYONES INPUT THAT WAS USEFUL. TIME TO GET HER BACK TOGETHER.
 
If u r 1 up at tranny and -2 down at Diff u may be ok. That’s a 3* difference. I personally like to see a 5* difference myself. Some ppl like less than 5* difference. Try it, if u don’t have much lift or spring wrap it may be fine. Is there a thin flat plate between ur tranny and the mount? It’s supposed to be there. It’s about 1/16-1/8 thick. Adding it may get u to
The 5* difference if u so choose. Do not have ur drive shaft in place, leave it off till ur done measuring. Kim
 
-
Back
Top