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Author Topic:   pinion angle?
steamatic racer
Member
posted August 20, 2002 03:15 PM
I heard people say 5 to 6 and some say 8 to 9 degrees. When I installed my 9" in my metric, the gauge read (6),but after all was finished it only had 2 to 3. I been running it this way until last week and tried to get (8) and did. My ? is 5 laps into the heat, driveshaft was found twised, bent, & in turn 3. Should I have left well-enough alone?? THANKS TERP


outlawstock17
Member
posted August 20, 2002 04:31 PM
was your driveshaft long enough? are your rear control arm bushings sloppy? did it come out going into the corner? it probably got twisted and bent up AFTER it came out. i run around 12 degrees with no problems. i haven't had a guage on the competitions differentials, but my eyeball says that some of them are running more than me. use the longest slip yoke that you can find and size your driveshaft about 1"-1.5" shorter than bottoming the yoke out in the transmission. this should give you enough room for movement without letting the yoke slide out of the transmission when you let off going into the corner.

hope this helps.

[This message has been edited by outlawstock17 (edited August 20, 2002).]

steamatic racer
Member
posted August 20, 2002 06:11 PM
After futher investagation of the driveshaft, the rear universal looks heavily damaged. It looked very heated-up and the ends of the universal;(not the cups):were chiped and 1 was broken off. Could this mean the uni. was in a bind? It was new & greased. The front 1 was good except for the needle bearings fell out and the cups were still in the yoke.(grease still present)!
I'd like to know: I took the upper trailing arms and drilled holes 3/4" away from stock hole towards the middle of arm. Or should I have relocated the upper or lower mounts on the rear-end? THANKS TERP


outlawstock17
Member
posted August 20, 2002 06:30 PM
the rear u-joint could've been bound up, but if the front of the driveshaft came out first it could destroy the rear u-joint when/if it digs into the track and tears itself loose. 8 degrees of pinion angle is plenty conservative, so i don't think that is the problem. my gut tells me that the driveshaft is too short or the rear control arm bushings are too sloppy, allowing the yoke to come too far out of the transmission. do you have a wheel hop problem going into the corner? when you relocated the upper control arm hole, did you weld a washer around the new hole? check the rear bushing in the transmission and see if it is excessively worn. it should have minimal play with the yoke fully engaged.

anybody else with some input?

steamatic racer
Member
posted August 21, 2002 08:39 AM
Thanks for your advice on all. Unfortunely the drive-shaft broke coming out of the corner. I beleive your right that if the drive-shaft was too short the thing could of came out and broke the u-joints, but when building the new shaft I was told to measure it w/ the yoke 1" from bottoming out. The tail-shaft bushing still in good shape and I for got to mention the yoke was still in the tail-shaft when the shaft broke.
I built a new shaft last night and installed new u-joints. Afterwards I notice the u-joint at the yoke was hitting on the shaft when in a "slight" angle. (this is yoke off broken shaft:- still in good shape). I located new yoke and will try it. You think that if the front u-joint was binding it would break? THANKS TERP


outlawstock17
Member
posted August 21, 2002 10:23 PM
yes, any binding could cause failure. it sounds to me like you've found the problem. i've seen guys use a die grinder to gain a little extra clearance between the yoke(front or rear) and the driveshaft. now go outrun 'em!

[This message has been edited by outlawstock17 (edited August 21, 2002).]

hughes
Member
posted August 22, 2002 09:31 AM
8 degrees is fine for a leaf spring car, but 2- 3 is all you need for a coil spring. If you run 8 degrees next week your drive shaft will be laying on the track again. If not then you'll be buying a new bearing for the front of your chunk. A stock coil spring set-up doesn't have that much movement. I mean your not running a four-link latemodel.


GnarlyCar
Member
posted August 22, 2002 08:31 PM
I noticed you said that you'd built a new driveshaft last night.. Just pulling stuff outta the air here, but are you sure the driveshafts were balanced correctly? You gotta remember that thing's spinning at engine speed, so even being a little out of balance could cause a LOT of damage.
I'd have to think about what Hughes brought up here as well. Your pinion angle should be dictated by how much wrap your axle housing has under load. A leaf car will wrap quite a bit more than a coil car, (Outlaw's car's a leaf car, so 12 degrees probably's pretty close to right for it) so it's entirely possible that you got too much angle in the rear u-joint for it to handle. Ideally, you'd like the pinion and the front yoke to be parallel under the engines biggest load, because the u-joints will also be parallel at that point and will not work against one another. The more difference between pinion angle and yoke angle, the more you're working the u-joints. Judging by your description of the rear u-joint when you found the shaft, I'd think you might have started at an angle that was beyond optimum, and went further away from that when you increased it. You might want to think about going the other way.
Incidentally, I've run nothing but coil cars in the 11 years that I've raced; have never run more than 6 degrees, and have never had a driveshaft or u-joint failure, even after running over 100 nights on the same u-joints in the same driveshaft.

Good Luck,
Matt


outlawstock17
Member
posted August 22, 2002 11:08 PM
79-up mustangs are a four link with the springs on the rear of the lower control arm very similiar to GM metrics. i use coil-overs relocated to the rear of the rear end housing. you guys got me thinking, so i just went out with a flashlight and re-checked my pinion angle. it is 8 degrees and not 12. i have to get all upside down and sideways to see the guage and i guess i read it wrong before. 2 degrees before 10, 2 degrees after 10. it's kind of hard to tell when you're all bent up under there getting dirt in your eyes. sorry if i goofed you up steamatic, my bad. i run 8 degrees, over 500 HP with boxed in stock lowers and adjustable tubular uppers with no failures......yet. i've only ran one race with it in this configuration as i've been adding a little pinion angle to it for the last 3 races. last week we were the undercard for the NCRA vs. All Stars sprints and the track was very, very tacky fast. it seems to me that if it were going to break, it would have broke then. every time i've added pinion angle, the car has gotten better forward bite. i WAS going to add a little more, but now you guys have got me scared to do it! every car i've had before this one was leaf sprung and i'm used to more pinion angle.

by the way, tulsa speedway is a 3/8 mile, medium banked, d-shaped track with long straightaways.

Darcy
Member
posted August 23, 2002 06:11 PM
hi racing jason we only run 3 to 5 max on our rear end our ones are the same as the metrics that you run other wise you are going to have the same problems that u r haven now send me a private message bye for now stay sideways


Dirtdiet75
Member
posted September 03, 2002 02:49 PM
Jason, bro, I'm glad you put the 650's in. Way to go! That's awesome. Talk to you later.


Scoot
Member
posted September 04, 2002 12:29 PM
Can you guys tell me how to check my pinion angle? Where to check it? And what tools to use? Thanks

------------------
Scoot
Smith Racing Team
870-365-5989


steamatic racer
Member
posted September 05, 2002 07:44 AM
Scoot, I went to my local ace-hardware store and bought a magnitic angle locator. I was told to find the flatest spot on the rear-end w/ the racer level.(not jacked-up)Hope that helps.
Thanks DIRTDIET75, Hope to do it again friday nite.Will you be there??


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