Spankrjs' 1984 Long Term Project

[spankrjs]

I installed double cardin(CV joint) then adjusted my rear differential so that the drive shaft runs perfectly straight with the diff. I've driven mine over 100 mph and there is no vibration at any speed. It's not rocket science. I also tried shims first. 2,4,6 and 8 degree. Once I decided to go with the CV joint and 6 degrees on the differential everything was perfect.
It's even more crucial on the front Differential because you are changing caster too, which is a whole new topic.
P.S. If you are going to use shims don't use the aluminum ones. They are soft and will wear out.
I was taught that u joints are good for up too 3 degrees and I've heard others say 5 degrees. At 10 degees that should feel like they are coming apart, and they will sooner or later.

It was good talking to you

Yep, I came to the same conclusion, just delaying the inevitable/holding out hope on the drive shaft I have

If shimming the pinion down 2 degrees doesn't work, then I will get the CV shaft made. Then, shim that, get it correct, then weld in new/longer perches

 

[craveman85]

I once had an 85 Chrysler that would boil fuel in the carbs when it was hot out. I put an oil cooler in my fuel line to cool it before it hit the carb. Probably not my safest idea ever. I vote to add a hood scoop

 

[zr10054]

It was good talking to you

Yep, I came to the same conclusion, just delaying the inevitable/holding out hope on the drive shaft I have

If shimming the pinion down 2 degrees doesn't work, then I will get the CV shaft made. Then, shim that, get it correct, then weld in new/longer perches

I always enjoy talking to another Scrambler owner especially if my past mistakes can help them out. I hope my info was of some help. I see a CV joint in your future.

 

[cbford]

I wrestled with this on a couple different rigs. I am not sure there is a ironclad answer, just variations and its up to you what you can live with. I certainly don't have a good answer but will offer some stuff I found and proved out.

If I understand what you are saying correctly:
-overall angle from x-case output to axle pinion = 16deg
-last test - you set opposing pinion angles to yield 10degree joint working angles and had no real vibration up to 60mph then mostly goes away at 75mph

If I have that right, that suggests parts wear, balance/straightness or phasing could be an issue. If it was strictly angle the vibration would only get worse the more rpm you turn the driveshaft.

Below is a chart I was given from Spicer that shows shaft rpm to optimal calculated angle of operation for small u-joints. You can calculate your shaft rpm by dividing engine rpm by final tranny/xcase drive ratio. (ex. if xcase = 1:1, shaft rpm = engine rpm/tranny gear ratio)
SHAFT RPM OPERATING ANGLE
5000 3.25°
4500 3.67°
4000 4.25°
3500 5.00°
3000 5.83°
2500 7.00°
2000 8.67°
1500 11.5°

I don't know your axle ratios and tire info, but I would guess if you have 700r4 behind the v8 in this you are in the 2000-2500ish range on this. So not too far out at 10deg, just losing service life.
But, the farther you get from the ideal operating angle the more factors like small dents, damaged weights, worn splines, worn yokes, axle wrap, etc cause problems.

Something else to keep in mind; if you go to a CV type shaft with same xcase to axle pinion angle, 16deg is getting pretty high as a normal operating angle for a standard CV. You may need to consider higher angle CV options to keep good service life.

 

[spankrjs]

I wrestled with this on a couple different rigs. I am not sure there is a ironclad answer, just variations and its up to you what you can live with. I certainly don't have a good answer but will offer some stuff I found and proved out.

If I understand what you are saying correctly:
-overall angle from x-case output to axle pinion = 16deg
-last test - you set opposing pinion angles to yield 10degree joint working angles and had no real vibration up to 60mph then mostly goes away at 75mph

If I have that right, that suggests parts wear, balance/straightness or phasing could be an issue. If it was strictly angle the vibration would only get worse the more rpm you turn the driveshaft.

Below is a chart I was given from Spicer that shows shaft rpm to optimal calculated angle of operation for small u-joints. You can calculate your shaft rpm by dividing engine rpm by final tranny/xcase drive ratio. (ex. if xcase = 1:1, shaft rpm = engine rpm/tranny gear ratio)
SHAFT RPM OPERATING ANGLE
5000 3.25°
4500 3.67°
4000 4.25°
3500 5.00°
3000 5.83°
2500 7.00°
2000 8.67°
1500 11.5°

I don't know your axle ratios and tire info, but I would guess if you have 700r4 behind the v8 in this you are in the 2000-2500ish range on this. So not too far out at 10deg, just losing service life.
But, the farther you get from the ideal operating angle the more factors like small dents, damaged weights, worn splines, worn yokes, axle wrap, etc cause problems.

Something else to keep in mind; if you go to a CV type shaft with same xcase to axle pinion angle, 16deg is getting pretty high as a normal operating angle for a standard CV. You may need to consider higher angle CV options to keep good service life.

Your RPM/degree chart is similar to what I have found. I am running 4.10 gears/33's/700R4.

My rear drive shaft seems fine. It is in phase, no twist or dents. All weights are still on it, slip shaft is good and tight, no slop. Both rear u-joints are still fine.

I "think" why mine is vibrating at the 60-70MPH range is because the soft springs are allowing the pinion to climb temporarily. Once I go faster, less torque and pinion is turning back down, if that makes sense I need a camera down there to see what is happening.

I would imagine the pinion starts to climb upon initial acceleration. But, at lower speeds, the drive shaft RPM is less then at interstate speeds, so no noticeable vibration. The combination of u-joint misalignment and higher drive shaft RPM at interstate speeds is causing the noticeable vibration. I am not sure why the vibration lessens at 75MPH, unless the torque the driveshaft is transmitting is dropping off, allowing the pinion to drop back down

The thing that doesn't make sense to me, and goes against drive shaft operating angle logic - When I had the pinion pointed higher, making that U-joint angle more severe/not matching the output shaft u-joint angle, it vibrated less

On the CV, I would be splitting the 10 degree single u-joint operating angle in half, meaning both CV u-joints would be operating at 5 degrees. The pinion u-joint would be pointed up, maybe 1-2 degrees down to allow for pinion climb, so close to 0 operating angle on that one. This is how I interpret it

 

[spankrjs]

I installed the 6 degree shims Friday night. The vibration is greatly reduced, but their is still a slight vibration. So, I am getting the current rear driveshaft modified for a double carden on the transfer case end. And of course, since I am running the Advance Adapter HD rear output, the correct 1-3/8" 32 spline CV yoke is not in stock at my driveshaft guys place, but I should have one here in a day or two

Plan on getting this thing operational for a local ride this Saturday

I would say that 90% of the vibration was eliminated once I installed the current shims. But, I know it can/should be better, so that's the route I am taking.

I have the most vibration 62-66 MPH, under load, all other speeds are about 90% vibration free. This 62-66 MPH vibration might be something else, tire, transmission/motor mount, will have to investigate further.

 

[MrBeep]

Working in a power plant for 40 years, I was taught ALL rotating mass will experience a vibration "Critical" at a particular RPM. Bringing the turbines up to speed required close monitering and planning to bring them through each as quickly as possible. When balancing them they were set up to have the least vibration at 3600 RPM operating speed on the high pressure and 1800 rpm on the low pressure which is their normal operating speed. Even the 600 volt DC motors had vibrations when we started them and shut them down. Just my .

When I make my drive shafts I static ballance them and if I have any vibrations at "Normal" driving speed, I will either grind a little weld off or add just a touch to fine tune.

 

[spankrjs]

Working in a power plant for 40 years, I was taught ALL rotating mass will experience a vibration "Critical" at a particular RPM. Bringing the turbines up to speed required close monitering and planning to bring them through each as quickly as possible. When balancing them they were set up to have the least vibration at 3600 RPM operating speed on the high pressure and 1800 rpm on the low pressure which is their normal operating speed. Even the 600 volt DC motors had vibrations when we started them and shut them down. Just my .

When I make my drive shafts I static ballance them and if I have any vibrations at "Normal" driving speed, I will either grind a little weld off or add just a touch to fine tune.

Well, I "might" have found what was causing the "critical mass" vibration at around 65 MPH, the rear output shaft yoke nut was not torqued down. Advance Adapters says the nut should be torqued to 150 ftlbs, it felt like 40 ft lbs I bought this HD rear output assembly from them, 100% pre-assembled. Well, guess I should have checked it out, or maybe the vibration worked it loose

I hope to get the new, balanced, rear shaft/CV/yoke back by Thursday

 

[zr10054]

Sounds like you are headed in the right direction now.

 

[spankrjs]

Sounds like you are headed in the right direction now.

I hope so, trying to get the new seal/yoke/driveshaft/pinion angle set before Saturday

 

[spankrjs]

Decided to freeze (well, realtively speaking, it was like 40 degrees LOL) my butt off last night and work on the Tan Scrambler's rear drive shaft issues.

I am using an Advance Adapter HD rear output shaft kit on my Dana 300. It uses a 32 spline, 1-3/8" shaft. That is all fine and good, but the yoke it uses is obviously different then a standard CJ yoke, and the yoke that came with mine is for a regular single u-joint. So, I did order/receive the correct 32 spline CV yoke. The only problem, the original Advance Adapter yoke has a seal surface of like 2", the new yokes is only 1-7/8". So, I had to install a new seal in the output shaft housing. And, I had to get some 5/16" diameter, 1.25" long fine thread grade 8 bolts. So, lots of running around the last few days.

Anyway, installed the new seal, installed the new yoke, installed the rear driveshaft.

I removed the currently installed "fat end toward the back" 6 degree shims, reinstalled some 4 degree shims, fat end toward the front to point pinion up. This was close, driveshaft running down at 11 degrees, pinion pointing up 13 degrees. So, pinion aimed 2 degrees too high.

Next, removed the 4 degree shims and installed 2.5 degree shims, fat end toward the front. Much better, driveshaft pointing down at 12 degrees, pinion up at 10 degrees. So, pinion is down 2 degrees, 1 degree preferred.

One note - on the 4 degree shim install, I simply tightened down the U-bolts, DID NOT TORQUE THEM, bolted on the tires, lowered the vehicle down to check. On the 2.5 degree shims, I TORQUED everything down, then lowered the vehicle. This might be why the 1.5 degree shim difference does not directly correlate to drive shaft/pinion angle degree changes.

I am going to leave it at 2 degrees down for now. The new main leafs will settle some, improving this angle. Also, I checked the angles with the Scrambler unloaded. Most of my long interstate travels involve 3-400 pounds of crap in the back, which should also slightly shift the pinion angle more toward the ideal one degree down.

Test drive tonight

 

[MrBeep]

Sitting on pins & needles.

 

[spankrjs]

The new CV rear driveshaft took care of most the vibration

Went to a little local ride at a dirt pit this Saturday:

I forgot how noisy the 1/2 soft top is compared to the 1/2 hard top

At interstate speeds, 70+ MPH, no vibration. Below 55 MPH, no vibration. But 55-65, the whole Jeep is vibrating, seems to be coming from the front driver side tire. So, alignment check/re-balance the tires tonight, should be ready for a "pick up a new engine for the red Scrambler" road trip on Wednesday

I have not checked the alignment/re-balanced the tires since before the South Dakota wheeling on rocks trip, or the air them down to 5psi Michigan trip, probably due. Wheel bearings, ball joints, TRE, all feel good. I'll check the shocks, too.

 

[spankrjs]

Had the tires re-balanced and the alignment re-set. The toe was off slightly, all five tire/wheels were out of balance.

That's not surprising, lots of wheeling and airing down tires will do that.

What was interesting, even using the "super great" Hunter Road Force balance machine, we noticed a problem it did not detect.

On the way to South Dakota, one of my front tires started vibrating really bad. Air pressure was fine, all mechanical stuff good. So, I put the spare tire on, vibration gone. When we went to re-balance this tire, it was of course out of balance. We carefully watched it spinning on the machine, without the guard in place. Looks like it is slightly out of round!!!!!! The tire guy thinks that a belt might have slightly shifted in the tire. No way to fix this. What was interesting, they were able to balance the tire/wheel assembly, and not too much weight. I think all five tires took around nine ounces each. IMO, that's not high on mud tires that have been used off road and on road a bunch. They are mud tires after all, not car tires Since they all took about the same weight, I would say all five are equally wearing.

Anyway, even though this out of round tire/wheel was balanced, no way it will ride "right".

Initial drive, the re-balance smoothed out slight vibrations below 55 MPH. I had slight vibes below 55 from the tires, being out of balance caused this, and they are mud tires, so they won't ride perfect, especially once they get some miles on them. That's just a fact of life.

From 55-60, most of the previous vibration is gone. But, right before 65, I have the same vibration. Once over 65, no vibration, and if you drive fast past 65, the vibration is minimal.

Of course, I did not think to inspect the other 4 tires for being out of round when they were spinning on the balance machine

I have a feeling maybe one or more of the other tires is out of round, too. I will have to out it on jack stands, put it in 4-Hi, see what they look like spinning on the Scrambler.

I rotated the tires at this time, too, front to back. That might have moved a "bad" tire to the back, less vibration from a rear mounted "bad" tire.

Anyway, the vibration isn't terrible, but it bugs me. It will be fine to go to Birmingham tomorrow, but if I can't get rid of this vibration, might have to get some new tires Before I do that, I will swap on the red Scrambler's tires to see if that gets rid of/or changes the vibration.

 

[wm69]

This is how I justify having several ATV's of the same model, several Jeeps of the same model, etc.

If you have "extras" you can troubleshoot by swapping parts around!

The wife, unfortunately, isn't buying it.

 

[rstickley]

Just a thought. I had a friend with a 67 Camaro that had a mysterious vibration. After a lot of money and time spent checking this and changing that, it ended up being a drum out of balance. Replaced it and all vibration was gone. I'm sure you have a few laying around you could swap out.

 

[spankrjs]

This is how I justify having several ATV's of the same model, several Jeeps of the same model, etc.

If you have "extras" you can troubleshoot by swapping parts around!

The wife, unfortunately, isn't buying it.

Yep, easy to look over at another one to see how to put them back together, too, better then pictures

Just a thought. I had a friend with a 67 Camaro that had a mysterious vibration. After a lot of money and time spent checking this and changing that, it ended up being a drum out of balance. Replaced it and all vibration was gone. I'm sure you have a few laying around you could swap out.

That is interesting, might try that, too

 

[spankrjs]

Drove this Scrambler to Birmingham and back yesterday, long day, no real problems.

With the old/new engine in the bed, about 6-700 pounds, no real vibration at 70 MPH, so that's where I drove it. With no weight in the bed, steering is OK. But, this Scrambler still has the original, 170,000+ mile steering box, has some lash at center. With the back weighted down, steering is OK at best at interstate speeds. I adjusted the box on the way to Michigan earlier this year, and took some lash out of it. But, I just need to replace the box. It leaks and is loose at center, so I just need to swap it before the next long road trip.

All in all, a good day. Picked up a new 4.0 to swap into my red Scrambler. Hesco used to build the new long blocks for Mopar back in the day, besides developing the MPI kit. This was their last "new" engine. They were using it on a dyno to test computers for the MPI kit. Since they can not obtain quality computers anymore, no need for the engine. It has had about 10 gallons of fuel run through it, so it is broke in.

A few pictures, seemed fitting to be picking up/hauling a replacement Scrambler engine with a Scrambler, even if said Scrambler has a GM 5.7

Not clearly pictured, but the engine is sitting on a steel cradle that sits on the oil pan flange, so the block is carrying the load, not the oil pan.

I dropped off the Red Scrambler's old engine to let Hesco rebuild, if possible. I it is still a good re-buildable core, if so, it will end up in my Green Scrambler eventually

So, another day, another day the Scrambler earns its keep as a pickemup truck

 

[Belizeit]

It's a real shame they can't find somebody to manufacture new computers for the mpi


Sent from my iPad

 

[b2esq]

A little birdie told me that FAST was developing a "Gen III" MPI controller for the 258. Such a computer may or may not soon be for sale by a company essentially synonymous with MOPAR MPI...