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spankrjs's Biloxi, MS '83 Scrambler

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
When I built my suspension I used a "L" bracket bolted to the axle and the "T" brake line fitting bolted to the "L" with the brake line to the frame pointing up.
More than enough length. Not sure if it's an option for you. :shrug:
That should work, and keep me from having to bleed brakes :thumbsup:
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
I have been driving this one the past few weeks, still very happy with the ride quality, nice and smooth.

One problem - I finally got it out on the interstate, and when it got up to around 65-70 mph, slight vibration from the rear end. I checked the rear pinion/Dana 300 output angles before the lift, they were both at 4 degrees, or pretty close to it (Dana 300 4 degrees down, rear pinion 4 degrees up).

After the lift, Dana 300, 5 degrees down, rear pinion 9 degrees up. I should have figured this would happen, the new shackles are much longer then stock.

IMG_20181201_093257851.jpg

According to the FSM, you should strive for the following (regular driveshaft, NOT CV shaft):

IMG_20181201_093250884.jpg

No problem, I have some steel shims left over from other pinion angle/caster angle projects. So, took it all apart, pulled out the center pins from the leaf springs, and a problem. I drilled all my shims center pin holes out to 3/8". IIRC, the Superlift and Rubicon Express springs use 3/8" center pins. The BDS springs use a 5/16 center pin. So, I ordered some new RE steel shims. They come with a 5/16 center pin hole. I also had to get some longer center pins, the BDS ones are too short to add a shim to the pack. Added bonus, the shims came pre-painted black, woo-hoo!!!!1

IMG_20181204_174112513.jpg


So, I added the shims, fat end toward the rear of the vehicle, to roll the pinion down 4 degrees. Put it all back together, got it back on the ground. nice and level, rechecked my angles:

IMG_20181204_193529453.jpg

So, according to the angle finder and the FSM, I should be good to go, I need to test drive to confirm.

I am going to assume that the longer front shackles have knocked the caster out of whack, too. I will probably get the alignment checked, unless I can accurately check the caster angle with my angle finder some how, before I add shims. On my other two Scramblers, with RE 4.5" lifts, that have longer front shackles, I had to shim the fronts to get the caster correct. So, more shims to come.

I also bought myself a Christmas present, and used it early:

IMG_20181130_203147949.jpg

A Dewalt 899 impact, and some impact sockets. All the years of working on these things, I have never had any type of impact, air or electric. This thing is cool. Works perfect for me. It easily took the lug nuts/u-bolt nuts, shock nuts off, no problem. Added bonus, no compressor or air hose to worry about, and since it has a battery, I can take it anywhere.

That's it for now, till I mess with shimming the front end :wave:
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
The rear end shims helped some, but I still have some vibration from the rear. Did some more math:

Driveshaft angle = 15 degrees
Pinion U-Joint operating angle = 10 degrees (15 degree ds angle - 5 degree pinion angle)
Dana 300 operating angle = 9 degrees (15 degree ds angle - 6 degree Dana 300 angle)

Random "internet knowledge"

"No more then 12 degree driveshaft angle with single u-joints one each end"
"No more then 15 degree driveshaft angle with single u-joints one each end"

33" long drive shaft divided by 10 = no more then 3.3 degree u-joint operating angle (I'm at 10 degrees)

(20,168/tire diameter) x gear ratio = driveshaft RPM at 60 mph
(20168/30) x 3.31 = 2,225 RPM at 60 mph
2,225 x 1.25 = 2,781 RPM at 75 mph

2,000 MAX RPM for u-joint at 8.67 degrees
2,500 MAX RPM for u-joint at 7 degrees
I'm at 10 degrees

It operates smooth up to about 60 mph, then it starts vibrating some. It's not terrible, minimal, but I don't like it. I had no vibration prior to the new springs.

One other thing I have noticed - my rear driveshaft has extended out about 1" more then before. I don't have any play at the slip joint, but maybe that is causing the vibration? I have another rear drive shaft, it measures 31-1/8" collapsed, that I had built for my Red Scrambler after I put the 4.5" RE lift on it. I might swap it on to see if the vibration goes away. I bet not.

So, unfortunately, looks like I might be heading toward a CV rear drive shaft on this one too, which seems crazy with a 2.5" lift on a Scrambler :shrug:

Going to go back and review my other two Scrambler threads and look at some of those drive shaft angles. I ended up with CV's on both of those.
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
I know I have a CV in the back of my Red Scrambler, but no info on my thread about it :shrug: I'm either losing my mind or never put any information on the thread about it :shrug:

On the Tan Scrambler, 4.5" RE lift/700R4/Dana 300/AMC 20, I had the following before the CV install:

Dana 300 = 5 degrees down
Pinion = 5 degrees up
Driveshaft = 15 degrees
Driveshaft length = 28-1/4"

This one vibrated with the 10 degree u-joint operating angles.

After the CV install:

Driveshaft angle = 12 degrees
Pinion angle = 10 degrees up (11 degrees would be better)
No vibration

I just cant wrap my head around the fact I have the same u-joint operating angles on a Scrambler with a 2" lift, I can see it on the 4.5" lift, but the angle finder doesn't lie :shrug:
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
Swapped in a slightly longer rear driveshaft and test drove it Friday night. I still have the vibration. It is perfectly smooth until 55 MPH, then it starts to slightly vibrate. The vibrations get worse as speed increases.

Ordered a CV Yoke/CV driveshaft this morning, and a slightly longer front driveshaft, too. Always something :wave:
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
Picked up and installed a new CV driveshaft/yoke for the rear, and a new longer front driveshaft yesterday:

1.jpg

The existing/stock front driveshaft might have been OK, but it only had like 1" more outward travel, better safe then sorry. The front driveshaft was made with same size tubing as the rear shaft, so slightly larger OD then a stock shaft. No clearance problems on this applications (258/T5/Dana 300/2.5" lift).

With the rear shaft, you have to change the Dana 300 yoke from the stock non-CV type to the CV type.

I flipped around the 4" shims I installed on the rear leaf springs (fat end toward front now), just to see if this would get me close.

My angles now:

10-11 degrees UP on the pinion
12-13 degrees DOWN on the driveshaft

So, the pinion is running 1-3 degrees DOWN from the driveshaft, 1 degree preferred. It is hard to make out the exact degree with my angle finder, but I am going to guess it is closer to a 2-3 DOWN angle.

Test drive confirmed the angle is still not correct. The vibration doesn't start now until around 65 MPH, so I am getting closer. I will swap in some 6 degree shims next, see what I get.

I am measuring the pinion u-joint angle on an actual u-joint cap. The rear end housing/yoke do not have a machined surface that runs the exact same angle as the u-joint. Bit of a pain, but the most accurate way to measure the pinion u-joint angle :twocents: I can also tell by looking that I have a bit more then the recommended 1 degree downward angle. With a one degree difference, the pinion yoke/driveshaft yoke would almost be parallel, and they are not.

Hopefully the 6 degree shims get it right :fingerscrossed:

A quick not about the shims - you can't necessarily go by what they are advertised as. An example:

Pinion angle, no shims - 9 degrees UP
Pinion angle, 4 degree shim, fat end to back - 5 degrees UP (9-4=5) WORKS OUT
Pinion angle, 4 degree shim, fat end to front - 10-11 degrees UP (9+4=13) DOESN'T WORK OUT

Also, when you change the pinion angle, you change the driveshaft angle some, too.

My driveshaft angle was at 15 degrees, with the pinion UP 5 degrees
My driveshaft angle is now 12-13 degrees with the pinion UP 10-11 degrees (CV shaft)

I am "scared" a 6 degree shim is going to make the pinion u-joint angle match perfectly with the driveshaft angle:crazy: That would be perfect with a linked rear end, but with leaf springs, you want the pinion a degree down to compensate for slight axle wind up. Or so they say......................

On my red Scrambler, with a CV shaft, I have zero vibration. I need to check the angles on it, and match
On my Tan Scrambler, with a CV shaft, slight vibration at exactly 60 MPH only, slower or faster then exact 60, no vibration.

IF I some how end up with the pinion u-joint/driveshaft angle exactly equal, I will probably slightly lift the engine/transmission to give it a slight misalignment. Lifting the power train will increase the driveshaft angle.

The vibration I have is slight, not super bad, just aggravating. Mainly feel it in the seat/floor boards, not audible. I know it should be running super smooth, so i will keep working at it.

That't it for now:wave:
 
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