When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
how to lower pinion on diff for driveshaft alignement
I want to lower the front of the differential. Suspension is all installed, but I need to shim the cushion ('donut') in between the chassis bracket and the differential bracket. Brute force does not seem to work to do this . I did loosen the bolts that hold the back crossmember to the big rubber isolation mounts (yellow arrows). I guess it's the tension caused by the suspension/spring that's holding it. Raising and offloading the wheels did not help though. Any suggestion how to squeeze the donut and some extra shims?
Stop over thinking, just put in snuber bushing and torque to 65 Lbs. Get it put together and then do the final adjustments, Jack
Hi Jack, I did stop thinking about it a while ago, angles for the driveshaft u-joins are just not within the 3° spec. I bet it's easier to adjust this now rather than when my freshly painted body is on. And because I can't adjust it now, it will be even worse later
Alex..I had the same situation when I changed differential and had to go to and offset u-joint. The offset part of the joint was too close to the body tunnel to suit me. I solved my problem by inserting a hard rubber spacer that I made from truck tire sidewall and inserting it between the new snubber bushing and the mount. It worked out perfect but I am sure some will bash me for it but good luck on your build.
well, I found a way out, after some 'thinkering' (apologies to all who believe I do too much of it ) where the tension forces came from.
I strapped the leaf spring under tension (one side only), and like magic the pinion came down so I can now easily shim it Should work too once the body is on.
A wood block and washers were inserted till I got the same angle both sides, 2° in my case. This way I know how muck to thicken the rubber donut.
Sounds good. From your other thread I think that was what you needed to do ( lower differential nose). Still not sure I buy that "W" u-joint set up.
Well, the choice is quite simple: the 'z' configuration with the equal but opposing U-joit angles each end of the driveshaft is impossible to do with the RS400 gearbox. May even be impossible with the standard muncie (don't know, has anyone ever checked?). The 'W' configuration is possible with equal same direction angles. So I take my changes assuming that the W configuration will behave as well as the many technical documents I read claim. I'll let you know within hopefully 6-9 months when the 64 should be on the road ;-)
You made me hesitate again about this 'W' configuration. Those who don't want to be reminded of their highSchool math, go to another thread
I went back to the maths of a u-joint and how in and out angles relate depending on the angle. As can be seen on the picture, the in/out angles relate to the COSINE of the angle. Well, the cosine of a negative or positive angle value is IDENTICAL, so the phasing (hence acceleration/deceleration effect on the shaft causing eventual vibration) between in and out is identical whether the angle is +2° or -2°.
With 'W' there is indeed some additional transversal bearing load but as far as I can assess this is minor and should not cause problems given the stiffness of the shaft and the size of the bearings in the gearbox and rear end. (those who disagree, let me know!)
As I said, we'll see when I finally go on the road
With the U-joint oriented as shown, it's showing BOTH the driveshaft and U-joint angles at the same time (they're the same).
Ok. I think I was reading too much into it!. The gauge is "zeroed" on the trans and then read on the driveshaft. The gauge reads the u-joint angle on that end of the driveshaft only. Not that both ends of the shaft have equal u-joint angles of 2 deg from that picture.
Your strap idea is a good one. I have found in the last few years those straps come in handy for many automotive uses. They can apply an amazing amount of force if needed.
What is the gauge supposed to be showing? Looks like driveshaft angle, not u-joint angle.
Tom
Well, the gauge was first put on the yoke, and calibrated to 0°. That's why the 2° you read is the relative angle between the gearbox and shaft and not the inclination of the shaft The gauge is actually an iphone, the app is Clinometer. The free version is ok, but lacks some features. I recommend the paying version, which at 0.99$ (yes!) or so won't break the bank. Another app that is certainly worth looking at is Garage Buddy, there is a free version and a pro versions at 0.99$ too. This screenshot shows part of what it does. Details here https://itunes.apple.com/us/app/gara...359760809?mt=8
well, I found a way out, after some 'thinkering' (apologies to all who believe I do too much of it ) where the tension forces came from.
I strapped the leaf spring under tension (one side only), and like magic the pinion came down so I can now easily shim it Should work too once the body is on.
A wood block and washers were inserted till I got the same angle both sides, 2° in my case. This way I know how muck to thicken the rubber donut.
Wouldn't it have been a lot easier to just shim between the diff and the cross member? I would not compromise the engagement of the crossmember nubs into the sombrero bushings, (donut) that is asking for trouble.
Unless you have an aftermarket trans that differs from the original, I would just leave it as designed. 100,000 examples came from the factory just like yours.
Wouldn't it have been a lot easier to just shim between the diff and the cross member? I would not compromise the engagement of the crossmember nubs into the sombrero bushings, (donut) that is asking for trouble.
Unless you have an aftermarket trans that differs from the original, I would just leave it as designed. 100,000 examples came from the factory just like yours.
tc
unfortunately, not 1 single car came from the assembly line like mine, cause my gearbox is not standard nor are the angles. Your concern about the sombreros is correct, but the 'twist' needed to give me the extra 3/8" on the bracket is very very minor. Does not seem to put stress on the system.
I thought about shimming the diff too, but that raises the suspension which I did not want.
As usual, it's all about which compromise to take, hopefully this is a liveable one
unfortunately, not 1 single car came from the assembly line like mine, cause my gearbox is not standard nor are the angles. Your concern about the sombreros is correct, but the 'twist' needed to give me the extra 3/8" on the bracket is very very minor. Does not seem to put stress on the system. I thought about shimming the diff too, but that raises the suspension which I did not want.
As usual, it's all about which compromise to take, hopefully this is a liveable one
The net affect between the diff and the frame will be the same either way you shim and your suspension will remain the same relative to ground level. (this is how the angle is changed between your frame mounted engine/trans and your diff)
What you are changing will add distance between your body/frame and the ground. This amount will be the same if you shim the diff or add rubber to your Sombrero mounts.
Messing with the sombrero mounts is a bad idea, but this is your project and your car.
The net affect between the diff and the frame will be the same either way you shim and your suspension will remain the same relative to ground level. (this is how the angle is changed between your frame mounted engine/trans and your diff)
What you are changing will add distance between your body/frame and the ground. This amount will be the same if you shim the diff or add rubber to your Sombrero mounts.
Messing with the sombrero mounts is a bad idea, but this is your project and your car.
Good Luck,
tc
You'r correct, got that too, but in my haste I typed 'suspension' while what I meant was 'body, and I absolutely wanted to avoid setting the body higher
I'll think again about your sombrero concerns
On the SWC I raised the differential 5/8 " with fabbed urethane bushings. So in order to get the pinion angle right I choose to relocate the front bolt on the pinion mount. The Nose needed to go Up. Easier said than done. I cut the reinforcing bars loose, re-positioned , drilled and welded back up. You really can't tell at a glance. In your case I think you can go the opposite direction.
I looked at the 'sombrero' problem, and eventual suspension impact.
Concerning the sombrero rubbers, the 3/8" lowering only marginally affects how they 'sit'. Does not feel like over stretching them all, to me....
Concerning suspension: lowering the pinion means that the leaf spring rotates a positive angle around the sombrero. This makes the ends of the leaf spring rotate towards the rear of the car. The geometry is such that 3/8" at the pinion translates to less than 3/16" at the leaf ends. I can hardly imagine this to be a problem, given that slack alone in bolting up the leaf spring may exceed that. One of the guys 'who know' on this forum reassured me in a PM that this should not be a problem given that normal wear&tear of a car has more impact than this one.
As TC said, at the end it's my car and my insight. Right or wrong, but I try to understand what I am doing. I'll let you know in 6-9 months how it worked out when the car is back on the road..hopefully
Last edited by alexandervdr; 09-27-2015 at 06:21 AM.
09-24-2015, 08:20 AM
how to lower pinion on diff for driveshaft alignement
) where the tension forces came from.
