Pinion Angle

cumminsdzl

cumminsdzl

Well-Known Member
Joined
Mar 20, 2005
Location
Wake Forest
So I went for my Toyota's first run yesterday at uwharrie and everything went very well. Its a great feeling to work on something for a year and take it out on its fist run with no true problems. But.....I am getting a rubbing/very light grinding sound when i am coming up any fairly steep hlls. It is very light and could be compared to the feeling of a tire rubbing a fender, but that isn't the problem. The truck has shackles that are 2.5 inches longer than stock and stock, very worn springs. The pinion angle has been compromised by the shackles. This being my first build of any kind, i wasn't sure if the angle was going to be a serious problem.

It seems like when i go up hill it takes the weight off of the front and transfers it to the back. This is allowing the front suspension to "droop" more than its usual ride height. Is it possible the rubbing feeling i am getting is coming from the front u-joint being put a too much angle? Any other ideas? I know the shackles arent the hot setup, but they are only a temporary thing, new springs will be installed this winter hopefully. If the pinion angle is my problem, would a degree shim be the best answer?

thanks for the help and sorry for the long post
 
You could build a drop mount for the other leaf spring mount to even out the angle. I know a lot of Ramcharger guys that do this and their stuff seems to work pretty well.
 
I don't know much about yota stuff, but I don't think 2"+ longer shackles would be enuff to cause an angle problem. I had no problems w/ 3"+ lift. Now when I hit 7" I had problems.
I'd check other things first. Maybe the d-shaft hitting something?
If it is and angle issue, it'll get worse when you replace the saggy springs.

Matt :huggy:
 
TheGeneral said:
You could build a drop mount for the other leaf spring mount to even out the angle. I know a lot of Ramcharger guys that do this and their stuff seems to work pretty well.
Click to expand...

That is a VERY bad idea. You don't just lower the attachment point for a front axle's spring. That also affects caster, which can dramatically change the road manners.

Nevermind drop brackets suck for ground clearance.
 
That is a VERY bad idea. You don't just lower the attachment point for a front axle's spring. That also affects caster, which can dramatically change the road manners.
Click to expand...

Its true it does affect caster but not if you have longer than stock shackles. I put 2" longer shackles on the front of my Yota and dropped the front attachment 2" to make up for it and gain a little extra lift. This way I got more clearance for tires, moved the attachment point forward to help the tires clear the firewall, and was able to still run a fairly flat soft leaf spring that flexes awesome. Drop hangers can have there weaknesses but when done right they provide great results with little or no negative issues.

As far as the grinding... Do you have a CV shaft or just stand u-joints in the d-shaft? Even if its a CV, toy CV's are not that great about angles unless you clearance them. Take a look at the CV and see if you can see shinny metal where its been rubbing on itself. If so then theres your problem.
 
That arguement would only hold true if your shackle was completely vertical. The greater your shackle angle, the more you reduced your caster.

Besides, bigger tires like more caster.. I'd leave it without dropping the hangar.. it probably did the alignment good.

His SFA Toy most likely has a double cardan (CV) front shaft, but the pre-IFS trucks have great angle of operation unlike the later IFS trucks that need the clearancing.

How about you lift the front of the rig a few inches and put an angle finder on the D/S and SEE what the angles are? We can hypothesise all day about it... and you can very possibly get misleading information.

A real fix would be to move the axle forward a little, and do a cut&turn on the knuckles, pointing the pinion at the t-case.
 
OK, i went and bought an angle finder and crawled up under the truck. The measurements are as follows: The front driveshaft runs at a 20 degree angle, the flange on the end of the pinion sits at 85 degrees. I think this means that sitting flat on the ground the pinion and the driveshaft are 15 degrees away from being correct. This seems correct in my head, but its been about 8 years since i took geometry :rolleyes: Does this mean i actually need a 15 degree shim in between the axle and the springs? That just sounds like a lot.

If these numbers seem way off, please tell me what i am doing wrong. I've read the info on 4crawler's website about 20 times and i still feel like im missing something.

I do have a double cardon front shaft, if this plays into what im saying.
thanks for helping the uneducated out.
 
depends on which side of vertical you measured the 85*, whether you're at 15, or 25...

But, do NOT just try and shim the axle.. your caster will suffer.

20* shouldn't be anywhere near the limit of your CV.. you can unbolt the D/S from the pinion and let it hang down to see for yourself.. mine is going to run at 30* static, though it won't live long.. :(
 
grinding

Have you looked under the vehicle? Under a load your rear joint could be hitting the cross member behind the t-case. This is a problem with duel cases, and also a e-brake on the rear of the t-case. Could be the shaft rubbing the fuel tank. Make sure the t- case out put is centered between the frame rails, it is adjustable with the t-case mount bolts on each frame rail. I doubt a u-joint will make a grinding sound, it would "just break".
 
I had the same type of knock/grind once... happened at Windrocks 3 years ago pulling a mile long hill climb. Sounded like a hub was stripped and was relational to torque. Tore apart the front hubs, nothing, joints were good, not problems found.

Happened again at URE the following month mainly when going uphill. Twisted it up on an erosion birm and a bud saw a broken motor mount (brand new 1 month earlier)... end up that the entire drivetrain was rotating starboard just enough that the front output of the TC was hitting the crossmember and chewing the yoke up. New motor mount and added a length of chain to limit the movement if, yeah right, when the mount gave way again. No issues with it to date... except the chain I used to hold it down that day came off & the fan chewed a nice hole in the lower rad. hose going up Daniel :mad:

So ditto, crawl underneath and *look* for what's rubbing/hitting/grinding...
 
Have you looked for rub marks on the yokes of the driveshafts to see if the u-joint is binding.... Also....what kind of springs and how much lift...etc...

Most people that build the minitrucks run a 1.5" -2" drop bracket in the front to level everything out once you put the bigger shackles on. You could look are Allpro's or Marlins. Most people just think you use them with a SAS but the are used the 85 are earlier models also.

If you could post a pic....i think it would help all of us understand...

Seth
 
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