Wheel hop in REVERSE?

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challenger57 said:
The tranny is a 833 OD , flywheel is nos for 360 clutch is centerforce diafram type. I tried backing off rear brakes no real diff. It's one of those things you'd have to feel to truely understand. Just don't know .
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Is the clutch new? People have been having issues with Centerforce clutches lately right here on this forum. I don't think it was specifically what you're experiencing, but there have been issues. I've never liked them. I've seen them weights fly off and cause all kinda mayhem, seen them chatter too......going forward. Who knows? I don't think it's your pinion angle UNLESS you are telling us incorrectly and it is SO FAR out that that's what's causing it.
 
My 2014 Grand caravan has a reverse that is seriously underengineered. If you put it in reverse and try to back up a hill, like a nose down parking spot, it makes all kinds of weird jerky movements. Quite a few pages on the support site.

Getting back to rear wheel drive solid rear axle classics...Generally you want the trans and rear pinion on a net zero setting on acceleration. Let it be 0,0 or -2,+2. On general driving, you want it down a few degrees. These are static measurements at rest. Remember your measuring in relation to your trans angle.
Suspension Recommended Angle
Using Full Wolfe Race Craft Suspension - all solid mounting points. -1 to -1.5
Half Solid & Half Poly Mounting points -1.5- to -2.5
All Poly mounting points -2.5 to -3.5
All Rubber mounting points -3 to -4.5
The more you get away from having all solid mounting points the more the rearend is going to try and rotate upward during launch. Therefore the more angle you must start with to prevent the angle from becoming positive (+). The idea is that when the rearend rotates you want the angle between the driveshaft and the pinion would be 0.
 
pishta said:
My 2014 Grand caravan has a reverse that is seriously underengineered. If you put it in reverse and try to back up a hill, like a nose down parking spot, it makes all kinds of weird jerky movements. Quite a few pages on the support site.

Getting back to rear wheel drive solid rear axle classics...Generally you want the trans and rear pinion on a net zero setting on acceleration. Let it be 0,0 or -2,+2. On general driving, you want it down a few degrees. These are static measurements at rest. Remember your measuring in relation to your trans angle.
Suspension Recommended Angle
Using Full Wolfe Race Craft Suspension - all solid mounting points. -1 to -1.5
Half Solid & Half Poly Mounting points -1.5- to -2.5
All Poly mounting points -2.5 to -3.5
All Rubber mounting points -3 to -4.5
The more you get away from having all solid mounting points the more the rearend is going to try and rotate upward during launch. Therefore the more angle you must start with to prevent the angle from becoming positive (+). The idea is that when the rearend rotates you want the angle between the driveshaft and the pinion would be 0.
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Exactly right. This is why the MP suspension book tells us the pinion should be 5-7 degrees nose down in relation to the transmission output shaft. So that when the vehicle accelerates, the pinion pulls itself up and becomes aligned parallel with the transmission output shaft. Of course, for "most" street cars, technically 5-7 can be a little much, but it will still work. No matter how much you preach it, you simply cannot get people to understand and do it.
 
RustyRatRod said:
Exactly right. This is why the MP suspension book tells us the pinion should be 5-7 degrees nose down in relation to the transmission output shaft. So that when the vehicle accelerates, the pinion pulls itself up and becomes aligned parallel with the transmission output shaft. Of course, for "most" street cars, technically 5-7 can be a little much, but it will still work. No matter how much you preach it, you simply cannot get people to understand and do it.
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Here is a question and food for thought. I read an artical strictly for mopar pinion angle and it states mopar factory at the tranny is set at 0 degree and rear should be 3 to 4 degree down. I get that and understand. I have tranny down at 2.4 degrees and no way can i tilt the tranny up any just no tunnel room. So here is my thought. I had it with 2 degree shims on the front side and if i slipped the clutch slowly it some what worked. How about i use a set of 4 degree shims. I had 1.5 degree down using the 2 so i figure the 4 should give me about 3.5 down . What do you think????
 
That’s what we have been telling u all along. U just weren’t listening to us. I can’t see why u can’t get ur tranny to zero unless ur motor is too high. Do u have the right motor mounts and brackets. Something is amiss. Kim
 
oldkimmer said:
That’s what we have been telling u all along. U just weren’t listening to us. I can’t see why u can’t get ur tranny to zero unless ur motor is too high. Do u have the right motor mounts and brackets. Something is amiss. Kim
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Motor mounts are correct, i actually had to use 2 1/8 inch shims under the k frame to get the oil pan away from the steering cross link so it would not rub the ooil pan when turning. I tried removing the to see what i might gain, only 1 half a degree. Car came with 273----a terd so i put a 360 in. Maybe a different oil pan and rework the motor mounts to get to 0.
 
The engine is always tilted down in the back by about 2* so the trans is probably correct. I have never seen the trans at 0*, the engine would have to be straight level. If you look at the intake manifold the carb is always lower in the front this puts it level when in the car. So you want your pinion about 0* so when you accelerate the pinion pushes up to about 1-2* then it should be good.
 
The driveshaft always goes downhill away from the trans, and the angle is always very shallow. As long as it is at least 1* then she's good to go. This 1* is strictly to to keep the needles shuffling around to not dig grooves in the crosspin. The angle can be more but there is zero reason to make it so, leave it alone.
Bolt the K tight to the frame without shims and
put the engine down on the mounts where it belongs, then
solve your engine clearances in the usual ways.
If you use all the proper factory parts, then it will fit with little to no fooling around.
As for the pinion angle; the softer your rear springs are, the more the engine-torque can wrap the pinion up. And if it goes just a lil nose up it makes a lil vibration. If it goes a lot nose up, it makes a lot of vibration. setting the pinion angle is in compensation for the springs. The snubber is also there to help control wrap-up, but should not be used only for that. Put the right springs on there for the torque the engine produces.
Playing with the pinion angle will not solve your problem.
IMO you have an engagement issue, probably aggravated by that jacked up trans mount behaving like jello, which may be modulating the Z-bar, and thus the TO fork, and thus the clutch-chatter.
After everything is returned to the factory engineered specs, and this includes especially the Z-bar orientation,then
the root issue will probably end up being clutch chatter due to contamination, or a warped flywheel or pressure-plate,pp.

BTW, raising the tail of the trans is totally the wrong way to go.

Keep in mind that the GROUND-PLAIN has nothing whatsoever to do with setting these angles. All settings are relative to the driveshaft. Nose down at the pinion means relative to the driveshaft. and the driveshaft must always go downhill from the trans. If you increase the rear nosedown, this will automatically increase the trans angle.
With my HO 360/CenterForce clutch/3.55s, the pinion angle can easily be varied 3 to 5 degrees with the vehicle stopped and the Line-loc set, simply by slipping the clutch. First the snubber will lift the car I'll guess over two inches. When the tires begin to spin,the pinion drops, and the rear deck falls. From there I can do anything with the gas pedal I want, and none of this monkey motion produces wheel-hop, with any tire I have installed back there.
Now; The engine is wearing factory biscuit mounts up front with a Schumacher engine tie-down. In the back is a poly late style spool mount, Slightly lowered for GVod clearance; maybe .25 inch at most. The rear has been lowered by de-arching the springs. and it wears 295/50-15s back there which are about 27" tall. The front was lowered as well to have a slight down-rake at the front. The K is about 5.75 to 6 inches from the road. So the snubber is very very close to the floorpan. What I'm indicating here is for comparison to yours.
I installed a second mainleaf at the back, full length, minus the eyes of course. My engine seems to make a lotta lotta idle-torque, cuz she's a dump-it and go deal at take-off with a starter gear of 10.97. I don't recall what angle I ended up with at the back, but probably in the range of 3 to 4 degrees, cuz she's a streeter. and traction-limited. Not to mention the leafs are really really stiff. There were times I had to remove the snubber, cuz it was pounding out the pan.Actually, I might not ever have put it back in after the drags in 2004. lol.Hmmmmmmmm
 
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I believe the book was giving an example with the transmission at 0* to make it simple to understand. They are telling you that "wherever" the transmission "is" the pinion should be 3-4* down "from that". .......just like everyone has told you all along.
 
RustyRatRod said:
I believe the book was giving an example with the transmission at 0* to make it simple to understand. They are telling you that "wherever" the transmission "is" the pinion should be 3-4* down "from that". .......just like everyone has told you all along.
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I understand what people have been saying, it's just that i have read so many articles on this and got mixed opinions. Now that i understand mopar is a different animal i can try what others have been saying, down with the rear angle.
 
Could it be something inside the differential?
Bad spring or something getting jammed then unbinding?
 
never say never; but I can't see it., But a bad front pinion bearing could allow the pinion to walk into the case. But that would make a heckuva clunk with every change in direction.
 
RustyRatRod said:
I believe the book was giving an example with the transmission at 0* to make it simple to understand. They are telling you that "wherever" the transmission "is" the pinion should be 3-4* down "from that". .......just like everyone has told you all along.
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Ok so here is my latest and greatest. I reversed the shims and no have a 2.7 degree down. Test drove and 100% better but still backing up a slight up grade i get some shudder not quite the thud i had before. So now i have a total of 5.1 between tranny down and rear down. I have a set of 2 degree shims, too much --' more or less to add.
 
challenger57 said:
Ok so here is my latest and greatest. I reversed the shims and no have a 2.7 degree down. Test drove and 100% better but still backing up a slight up grade i get some shudder not quite the thud i had before. So now i have a total of 5.1 between tranny down and rear down. I have a set of 2 degree shims, too much --' more or less to add.
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I would go "a little farther down" on the pinion angle. The angle you are looking for actually is the working angle, which is the difference between the two. Mopar never really looked at it that way. They always gave the two angles separately.
 
RustyRatRod said:
I would go "a little farther down" on the pinion angle. The angle you are looking for actually is the working angle, which is the difference between the two. Mopar never really looked at it that way. They always gave the two angles separately.
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Well i added the 2 degrees more this morning so now i have a down rear of 5.1. . I don't see much if any diff from last time. If i slip clutch i can make it work. Don't know what else to do. All bushings seem good, motor mounts seem good. If any of yall live in york pa and want to take a swing at this thing, literally a 10 pound sleg swing i can make it happen.
 
challenger57 said:
Well i added the 2 degrees more this morning so now i have a down rear of 5.1. . I don't see much if any diff from last time. If i slip clutch i can make it work. Don't know what else to do. All bushings seem good, motor mounts seem good. If any of yall live in york pa and want to take a swing at this thing, literally a 10 pound sleg swing i can make it happen.
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Might end up being a clutch issue. I've never seen a clutch chatter "only" in reverse, but there's a first time for everything. Have you checked the transmission mount?
 
RustyRatRod said:
Might end up being a clutch issue. I've never seen a clutch chatter "only" in reverse, but there's a first time for everything. Have you checked the transmission mount?
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I can't remember the ratio but you can get clutch chatter in reverse and not in low gear. It's the way the chassis gets loaded while backing up, the extra ratio of reverse and the pulsing of the firing cylinders on the crank.

You sometimes see this when the disc doesn't have a marcel in it. The thin, wavy spring between the clutch materiel and the disc itself. Or an unsprung disc can do that.

The real cause of all those issues listed above is from too much plate load without a marcel or an unsprung hub or both. I run an unsprung cintered iron disc and don't have the issue of clutch chatter in either direction, but about the highest plate load I have is about 1000 pounds. If I put 2400 pounds on it, it would rattle my teeth out, and probably shake the dash right off the car.
 
yellow rose said:
I can't remember the ratio but you can get clutch chatter in reverse and not in low gear. It's the way the chassis gets loaded while backing up, the extra ratio of reverse and the pulsing of the firing cylinders on the crank.

You sometimes see this when the disc doesn't have a marcel in it. The thin, wavy spring between the clutch materiel and the disc itself. Or an unsprung disc can do that.

The real cause of all those issues listed above is from too much plate load without a marcel or an unsprung hub or both. I run an unsprung cintered iron disc and don't have the issue of clutch chatter in either direction, but about the highest plate load I have is about 1000 pounds. If I put 2400 pounds on it, it would rattle my teeth out, and probably shake the dash right off the car.
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Here is something i have been thinking about. When i originally put the conversion in i used a ram clutch with the 3 fingers and trying to use a hydraulic setup. I found out you can't use hydraulic throw out and 3 finger clutch. So i kept the disc and bought the centerforce diafram pressure plate. Could the mismatch be the issue. I think the centerforce is actually stronger than i need, it grabs pretty hard right off the bottom.
 
challenger57 said:
it grabs pretty hard right off the bottom
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I found the same thing with a CFII disc.
My cure was to install a factory from the dealer 340 disc, and I spaced the CF away from the flywheel the thickness of a hard washer, guessing .040 or a bit more.. It also makes taking off, a dump it and go deal with a 10.97 starter gear. If I need more clamp I just rev it up a lil higher.
The penalty is that the 340 discs don't last all that long, and if I be mean to them, they flat out give up; usually spitting out the springs and or cracking out the centerhub. No biggie, on a 4-post drive-on hoist,my record is 17 minutes to drop the unit, which includes dropping the GVod and dual exhaust. Most of that is disconnecting and removing the shifter.
I got a Passon box and side-cover, making the A833 about 85 pounds; making it a slam-dunk to install.
 
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