Mcgaughys 2/4 Wobble Solution - Pinion Angle

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R/T_Fire

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Damn, that was some reading... basically its a speed wobble. Ive never had that from a pinion angle... but still something I'm going to look into.
There are alot of little quirks I've noticed with my truck... just got to identify them all right and weed out the others... I plan on upgrading all the rear set up anyway and eventually designed a Watts link when I get more radical with the driving..

As for my tail waggin. I don't have that at all.. damn thing is solid like on rails... my issue is more a vibration balance issue. oh and its speed related.. and before anyone mentions it yes I've had my tires balanced and rebalanced.

Thanks for that long winded write up though.
 

charonblk07

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The joys of a 4-link suspension. Leaf springs are so much easier to deal with, a set of lakewoods, a pinion wedge and you're good to go.

It's funny because everyone talks about designing a watts link, hell, I had everything drawn up when I did my suspension rebuild but found the gains over a properly setup panhard bar system are minimal unless you have a long travel suspension or go to the road course where you can apex a corner and lift one side of the suspension at speed. The 4.5" of suspension compression I have just didn't warrant the extra cost for a 1/4" less lateral travel.

Have your driveshaft pulled and balanced, you'd be surprised at what a 25g difference can make at peak RPM.
 

R/T_Fire

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Drive shaft Balance is on the list of things to do, just kinda hard till I get the blazer's trans built, have had no time with this Cali fire season and baby on the way to tear it out to get on it or any other things on the list... But hopefully I'll see a few more strike teams to put a 5-10k bonus ontop my 5k work bonus at the end of the year for all these projects

I have a idea for the watts link that uses some parts of a harvester that has similar motion of parts and has a pre-engineered unit that has a bearing and brackets and such.. all i need to do is come up with some mounting brackets and make my links...

But I do plan on playing with this truck on a track and it will be strickly a toy so its worth it to me.. but that's low on the fab list. so realistically I'll never get to it :roflsquared:
 

MarineRam

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Thanks for posting. I am new here.

I installed Ground Force kit #9864 on my R/T. The kit included a spacer for the transmission tail to correct drive angle. I installed the kit with adjustable track bar and adjustable end links.

I am absolutely disappointed with the ride. On freeways, uneven roads, and at high speed, the wobble is bad and it's worse with a full tank of gas.

I must say tho, the wobble is not present on smooth roads.

I dislike it so much I am going to remove it and try something else.

As far as track bar angle, I did not drill. The angle isn't so far off that it would cause such a bad wobble.

I appreciate other's input on relocation bracket, adjustable LCA's, sway bar, watts, etc. but at this point I am turned off and not willing to throw money at it for a simple appearance mod.

What I haven't seen/read is comment on LCA angle- similar to what the Camaro guys dealt with when lowering their rides. Part of their issue was solved by bolt-in or weld-on relocation brackets for the axle side to correct LCA angle. The preferred angle was to the have the axle side (rear) lower than the front.

Good reading. Thanks dudes
 

charonblk07

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Thanks for posting. I am new here.

I installed Ground Force kit #9864 on my R/T. The kit included a spacer for the transmission tail to correct drive angle. I installed the kit with adjustable track bar and adjustable end links.

I am absolutely disappointed with the ride. On freeways, uneven roads, and at high speed, the wobble is bad and it's worse with a full tank of gas.

I must say tho, the wobble is not present on smooth roads.

I dislike it so much I am going to remove it and try something else.

As far as track bar angle, I did not drill. The angle isn't so far off that it would cause such a bad wobble.

I appreciate other's input on relocation bracket, adjustable LCA's, sway bar, watts, etc. but at this point I am turned off and not willing to throw money at it for a simple appearance mod.

What I haven't seen/read is comment on LCA angle- similar to what the Camaro guys dealt with when lowering their rides. Part of their issue was solved by bolt-in or weld-on relocation brackets for the axle side to correct LCA angle. The preferred angle was to the have the axle side (rear) lower than the front.

Good reading. Thanks dudes

A few of us have corrected the LCA and UCA angles but it's not normally an issue until a 6" rear drop where you start having interference issues between the LCA and the UCA frame mount. The adjustable LCAs and UCAs will correct the pinion angle and at 4" drop the arm angle isn't that much of a concern and because of the location of the axle mounts it's not a simple weld-in job if you're keeping the factory frame mounts; there's quite a bit of custom work that needs to be done to realign everything, $2500 worth actually.

suspension2_zpsee2b4412.jpg
 

Dubstep Shep

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The joys of a 4-link suspension. Leaf springs are so much easier to deal with, a set of lakewoods, a pinion wedge and you're good to go.

It's funny because everyone talks about designing a watts link, hell, I had everything drawn up when I did my suspension rebuild but found the gains over a properly setup panhard bar system are minimal unless you have a long travel suspension or go to the road course where you can apex a corner and lift one side of the suspension at speed. The 4.5" of suspension compression I have just didn't warrant the extra cost for a 1/4" less lateral travel.

Have your driveshaft pulled and balanced, you'd be surprised at what a 25g difference can make at peak RPM.

I've driven cars with a lot less travel than these trucks, even when lowered, and the watts helps them tremendously.

It may not sound like much, and on paper it doesn't look like much, but it takes A LOT of energy to move that axle and suspension a quarter inch, and that energy reacts on your vehicle.
 

charonblk07

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I might have taken a pic or two when I was in there. It's a fully articulating caged crawler built by the same shop that did my suspension. Thing is insane and has a crazy amount of articulation.

d97744783ebc4e943d340cd53d1e9529.jpg



Sent from my iPhone using Tapatalk
 

charonblk07

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I've driven cars with a lot less travel than these trucks, even when lowered, and the watts helps them tremendously.

It may not sound like much, and on paper it doesn't look like much, but it takes A LOT of energy to move that axle and suspension a quarter inch, and that energy reacts on your vehicle.

Most cars don't have the room to do a long panhard bar like the truck so because we are not restricted by the packaging issues that most cars have to deal with we can run a longer panhard bar; the longer the panhard bar the less lateral deflection there is when the system cycles. Also, I pulled 1/4" out of my butt when I wrote that, the total lateral deviation with my 38" bar is 0.2" which is ~13/64". Now, the geometry from the Watts link gave me a lateral deviation of 0.1" at the same vertical deviation which is ~7/64". A difference of 3/32" lateral deviation between the two systems is NOT going to make any difference until you take it to a race track where the tires are already taking full lateral loading as they lean out around the corners.

Keep in mind the scope of what these trucks are used for, even being pushed hard on mountain roads, it's just not worth doing a Watts link unless you want to do one just to say you've done it or you will be taking it to the road course and running it in class races. Do you really think both Richard and I who was/are pushing the 4th gen suspension abilities both decided against watts links just because it was too much work or would cost too much to build? No, it was because the gains weren't there over upgrading what we currently have.
 

Dubstep Shep

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I'm curious, how are you calculating the lateral deviation for the watts?
 

charonblk07

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I'm curious, how are you calculating the lateral deviation for the watts?

Two ways. I went old school first and built a 4:1 scaled mock up of the dimensions I calculated for the links and traced the full figure 8 and measured the lateral deviation at the 4.5" vertical travel mark. I was surprised at how much deviation there was so I had a friend put it together in SolidWorks and she measured the travel and came up with a number that was within .005 of my number.

I had thought about pulling my old math text books out and doing it that way but I honestly was getting a headache remembering why I hated doing my math minor.
 
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VeDubb

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TL;DR: Pinion Angle

I know, another wobble thread, how original. My solution was found by my friends dad who was in the Canadian Rally Championship in the Late 90s and has experience with both lowered cars and trucks both personally and professionally.

My 4WD single cab shortbox Ram wobbles significantly when exceeding 90 MPH and only gets worse as I accelerate. Nothing in this thread is to discredit anyone I asked for advice or any other thread on RF's. I will add good quality pictures after work possibly to aid others hopefully. Here is the steps I went through including what realistically was accompanied by 10's of hours of research and note taking. All Mcgaughys parts I reference were from their 'Deluxe Drop Kit - McGaughys Part# 44050'

Step 1:
Took my truck in for alignment, tire rotation and balancing. No real noticeable change.

Step 2:
I had my front left CV which was failing from unknown reasons replaced under warranty and had the dealer also align my truck while It was in for warranty work.

Step 3:
Under advice of other 2/4 owners and Hemi450HP, I purchased a Sphon Adjustable Panhard Bar. It was installed in combination with my Mcgaughys panhard relocation bracket and adjusted to get the tires as close to possible using a plumb bob and tape measure. It was noticed that the tires seemed to have a very slight camber in, where the tops appeared to be slightly farther under the fender than the bottoms. Tires were checked for bulging and wear and were ensured to be at the proper PSI and had the lugs torqued to spec after.

The wobble felt as noticeable as ever before even with the panhard adjusted and triple checked to ensure it was also torqued and installed correctly.

Step 4:
Next up was the Hellwig Rear Sway Bar which bolted right up as-per the instructions to the Mcgaughys shortened end-links to the most aggresive frontward mounting point on the bar. This aligned the bar perfectly horizontal, everything was torqued back to Chrysler's specs and double checked. The panhard was also double checked after to ensure both bars together had the axle were where it should be. One comment about the sway bar, its quality is amazing, also ensure you are installing it in the exact same orientation as stock, I am pretty sure its not symmetrical and has a left and right side one causing the center to be higher than the other orientation (possibly contact panhard or diff) but I don't know if that's labelled or mentioned in the instructions. It can be done done on your driveway with most of the proper tools but if I had a lift it would have taken 1/4 of the time that it did.

The truck's rear end feels solid when taking corners at high speeds such as on-ramps, you still feel the wobble over bumps and at high speeds but its just a stiffer wobble instead of being mushy like it was before. This wobble is much safer and much easier to handle for the average driver, I can see how some people feel confident calling this a fix, I want next to no movement at high speeds. So I am not done.

Step 5:
I have QA1 rear shocks ordered, TS905's that Hemi450HP verified to be direct bolt on's and no modification needed. Will verify when they arrive. In my eyes the rear shocks are no good. The rear is dropped using coils and changed 4", 4" results in a very large angle change in multiple components of the stock set-up and I think shocks are one of them. I believe that the factory shocks add to the wobble because they are not operating at their optimum angle nor design distance like they do when the rear is 4" higher.

Wondering if I NEED to replace the front shocks also or if only the rears will be acceptable. I personally think the front ones will be fine because we used a spindle drop which is intended to keep the front geometry AS CLOSE AS HUMANLY POSSIBLE to factory while still achieving a drop. At the cost of pushing your tires out 1/2" - 3/4".

Step 6:
My friends dad who was in the Canadian Rally Championship in the Late 90s and has experience with building and working on both lowered cars and trucks, especially suspension wise, both personally and professionally looked at my truck and very quickly told me my pinon angle is off and that it is causing wheel hop. These problems compound together and causes the rear end to eventually start wagging or wobble even with Step 3 & 4. I am in the process of calling Spohn or Matt (whoever can get me the delrin bushings the easiest) and ordering Spohn Upper & Lower Rear Control Arms in order to recenter and correct the pinon angle to one that is correct for the new geometry of the truck and the way I want to drive it.

He mentioned over text message to me if I wanted to almost ensure this was the problem I could by: Removing/unbolting/undoing what holds the rear drive-shaft in safely and drive the vehicle in 4WD. It would be very unorthodox and something you don't want to do for a large distance or time period AT ALL but it could confirm if the drive-shaft/angle is the culprit. I'm not going to try this even with his help, I wanted the control arms anyways this just gives me justification to spend more $$ without feeling guilty. After I install them, adjust them the best I can and most likely take it to a professional alignment shop and let them adjust all the Spohn components in combination with the rest of the truck I should see no wheel hop at any speeds and definitely no more wagging or wobble. I will be putting on perfect Nitto 420's that are staggered to account for the 1/2" - 3/4" that the front spindles push out the front tires and the tires will be perfectly aligned and weighted.

Step 7:
Profit??

I should have no excuse within a couple weeks time. I hope this might help anyone currently with problems that is on the fence about the Spohn Upper and Lower Rear Control Arms, or anyone in the future with problems as well. I will post again when I get the Shocks and the Control Arms in. If anyone can tell me if not upgrading the front shocks is acceptable or not and if it isn't which shocks I need? Thanks.

I now have this problem after a 2/4 Belltech drop. I was convinced the problem was in the front not the rear, and was surprised to read so many posts regarding the rear. I have airbags on the back, and it doesn't seem to matter how much air is in them the wobble doesn't change, which is what lead me to think its the front. Hmmmmm?
 

VeDubb

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Update on my wobble issue. I spoke to a tech at McGaughys and told him about the wobble issue and my set-up. He said with the track bar relocate bracket it shouldn't wobble. When I said I have airshocks (need to maintain hauling capability) he said that's the wobble problem. I replaced the air shocks with air bags in the coils springs and put the belltech nitro-drop shocks on the back, and viola, wobble issue solved!
 
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