Pinion angle help (1 Viewer)

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Feb 18, 2004
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Seattle, WA
See the attached picture- I need some help setting the rear pinion angle, as I'm in the process of doing a spring over on my 73 fj40. I've got a double cardan driveshaft off an 85 minitruck that I'll be using. The degrees on the TC face and pinion are relative to a verticle plane, the driveshaft angle is relative to horizontal. With the perches tacked in place, the pinion is pointed a little low. Am I going to be okay, or should I rotate the pinion up further?

Thanks for the input!
pinion.jpg
 
you want the pinnion to point straight at thetrasfer case output(W/ a CV Joint). so idealy the pinnion and driveshaft have the same angle..

I bet that setup would be just fine the way it is.. Rotating it up gets it out of the rocks a bit, but makes the rear cover more venerable.. and you may get a little less gear oil to the pinnon bearings.. Mine points up!
driveshaft.JPG
 
Thanks Isotel. I guess I was feeling lazy for a minute, but since I only just tacked the perches in place, it shouldn't be too hard to get them off and reset them to get the right pinion angle.
 
Mad Chemist said:
See the attached picture- I need some help setting the rear pinion angle, as I'm in the process of doing a spring over on my 73 fj40. I've got a double cardan driveshaft off an 85 minitruck that I'll be using. The degrees on the TC face and pinion are relative to a verticle plane, the driveshaft angle is relative to horizontal. With the perches tacked in place, the pinion is pointed a little low. Am I going to be okay, or should I rotate the pinion up further?

Thanks for the input!
Howdy! You want the regular ujoint to be within 2 degrees of straight, and let the CV do all the angle work. I'm running this setup on both ends of my Piggy. Works great. You may want to add another filler hole to your diff cover. In stock configuration, the gear grease level should hit the pinion bearings. I raised mine several inches. I already snapped one pinion between the bearings from running dry, so I ain't doin that again!! John
 
Ditto to inkpot. I set mine at 3-4 degrees though. You have 14 as shown and is probably going to vibrate.
 
Thanks guys. In terms of matching the pinion angle to the driveshaft angle- having it set to 3-4 deg positive (with the pinion pointing a tinge below the transfer case) will bring it closer to zero under compression, but will increase the deflection angle >4 deg. under droop, right?
 
Yes, you are correct. But are you worried about your DS vibrating when you are airborne?
 
Ha ha ha! Lets just say I'd rather not test that one out, just wanted to make sure I was completely understanding you .
 
thread revival...

i put my atlas in tonight (putting in mercedes OM617 nv4500 atlas) with a spring over. springs are 60 series built 1 inch under stock height. trying to keep it as low as i can with the spring over. here is my rear pinion angle. it's 30 degrees up from horizontal when pointing right at the atlas output flange. with double cardan joint is this right? seems really steep.
IMG_3705.JPG
 
:bang: looking at things a little more critically i think i need to drop my whole drive line down about 3 inches which will help with that angle. currently my output shaft is a bunch above the frame and that's too high. this make radiator clearances more difficult
 
Yes I think you need to lower everything. Your rear output should be equal height to the middle of the frame rails give or take a little bit. Which according to the pic would seem you need to move it more than 3 inches. You can also tilt the whole Assembly about 2 or 3 degrees to help get the rear output lower.
 
yeah i think i need to drop it and tilt the whole drive line. it's parallel to frame rails at present. my biggest concern is as i angle the drive line my fan becomes less parallel to the radiator and i don't want to cause worsening interference. i guess this is where the fine tuning will happen! at least everything is only tacked in so not to hard to move
 
Fine tuning takes forever. But being thorough is worth it. To me the rear output looks like it is either above or at the top of the frame rails. You want it lower more like the first pic in this thread. I wouldn't tilt it more than 5 degrees personally. I think stock is 2 degrees but Im not positive. Your going to of course have to make some compromises here and their to make everything work. I think that motors oil pan design may hinder you from lowering everything to the ideal spot.
 
yeah when i put the atlas on i went "oh crap". that's not right. it is indeed above the frame rail. a bit of tilt and drop the whole height will be the course of action. with tilting it i think ill go back to electric fan so the fan stays parallel to the rad. it won't gain me much space but will prevent the fan from hitting the rad. ill carry on my adjustments in my build thread!! thanks guys for your responses. confirms what i though i needed to do
 
Make your final pinion angle determination with the rear of the truck fully loaded. The angle of the pinion can change as the springs compress.
 
clock the atlas up a little and set it so the bottom of atlas is even or just above the bottom of frame, lower radiator if nec.
 

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