60Patrol

The mean green suicide machine... The El Paso Deathtrap.

(Go to my post in this thread to find out why I have cooked up these nicknames: http://www.60patrol.com/forum/viewtopic.php?f=2&p=14739)


I should start this thread with an image of this Patrol, taken the day after I brought it home:



... It hasn't looked like that ever since. Originally purchased as a non-running parts donor for my "other" Patrol project, soon after buying this one I got the engine running and discovered that it actually ran very solid- it made 110+ psi of compression across every cylinder, and pulled over 15 inHg of vacuum... At that point I decided that rather than parting it out, I would take what I needed off of it, and then use whatever was left to make a fun, topless, weekend offroad cruiser... This thread will chronicle that project.

This week was a good one for the Marty Robbins Ebay Patrol - I (finally) got a clean Arizona title issued that has the L60-00511 vehicle ID as the VIN, and I began the project to re-do someone's very dangerous previous attempt at a spring over axle (SOA) conversion. The front axle's SOA conversion has to be completely dismantled, and the person who did it did not even bother to convert the rear- they just wedged some coil springs over the rear axles to add some additional spring rate, so I decided to begin the re-build by completing the rear SOA swap.

First order of business was to tear out everything that was there:



Since the rear springs in my red Patrol are WAAAAAY more flat than the rear springs in the green one, They will work better for the spring over conversion, and should add the 3 inches of lift necessary to level the rear out with the front, so out came the rear end from the red patrol as well:



And what I though was the best score of the day- I actually managed to dismantle a complete, and reuseable pair of spring shackles:



That was how far I got today... Next steps are to get the spring pads cut off the axle tube and get them cleaned up to flip to the other side, and to get the springs from the red Patrol mounted under the green one, and flip the center sheer pin on the springs... more updates to come.

This should be interesting.

Well, after a week spent on the east coast on business, I was excited to get home this weekend and get some more time in on this SOA project, but as soon as the plane landed, I realized Mother Nature had other plans... it's been raining non stop since Thursday night (yes, it does rain in Phx from time to time )

This afternoon the rain broke for a little bit, so I did manage to bust out the Plasma cutter and remove the spring perches from the axle. I'll tell ya, even my "cheap" Harbor Freight plasma cutter was still pretty pricey (even with the coupon); but man, they make SHORT work (like 5 minutes) out of what would take an hour with a grinding wheel:





Another 30 minutes with the course grinding wheel, followed by the flapper disk, and the axle tubes are all smoothed up and ready for the spring mounts to be re-welded to the other side:



Tomorrow I'll clean up the rough edges on the spring pads with the grinder, and get the center pins on the leaf springs flipped around, and if the weather cooperates again, maybe I'll be able to get it all mocked back up in the Patrol, and get the pinion angles set up to re-weld those spring pads...

Cool! I've never seen someone do this before. Good stuff.

If I remember right, on an old Jeep CJ, a SOA conversion would net about 6" of lift? The good thing is it virtually maintains the same road manners. I bet whoever did the front didn't realize what kind of job it is and decided to not tackle the rear.
While you have it apart, are you going to rotate the axle any to help with drive shaft angle?

I don't believe it's a good idea to change the angle of the rear end input shaft to reduce the angle on u-joints. Generally the transmission output shaft and the rear end's input shaft should be parallel with each other. Then the u-joint angles on either end roughly match which helps limit vibrations. If they end up being large (something like 15-degrees from C/L) then you may end up with vibrations at speed anyway. If this is the case, then you can consider aligning the pumpkin to point directly at the tailshaft of the transfer case so then rear u-joint is at 0-degrees of angle and then add a CV joint at the transfer case end of the driveshaft.

Anyway, there's my two cents and, trust me, worth every penny!

John

faux40 wrote:I don't believe it's a good idea to change the angle of the rear end input shaft to reduce the angle on u-joints. Generally the transmission output shaft and the rear end's input shaft should be parallel with each other. Then the u-joint angles on either end roughly match which helps limit vibrations. If they end up being large (something like 15-degrees from C/L) then you may end up with vibrations at speed anyway. If this is the case, then you can consider aligning the pumpkin to point directly at the tailshaft of the transfer case so then rear u-joint is at 0-degrees of angle and then add a CV joint at the transfer case end of the driveshaft.

Anyway, there's my two cents and, trust me, worth every penny!

John

WARNING: I am not a driveline guy.
I forgot about that. I was just thinking about u-joint binding issues with 6+" of lift on a vehicle with a short drive shaft. Excessive angles can cause issues as well.
What you said is what I was thinking of. Using a double cardan driveshaft. That is what my son was going to do on his SAS Frontier in the front until he rolled the truck.
But, I think I remember reading diff lubrication can be an issue with this setup.

Wow- lot's of questions/topics to replly to... one of my trademark long posts, coming right up

mdawg4x4 wrote:If I remember right, on an old Jeep CJ, a SOA conversion would net about 6" of lift? The good thing is it virtually maintains the same road manners. I bet whoever did the front didn't realize what kind of job it is and decided to not tackle the rear.
While you have it apart, are you going to rotate the axle any to help with drive shaft angle?

I think the front was probably converted out of necessity, because one of the original passenger side spring plate bolt bosses that is cast into the pumpkin is broken off and is totally un-repairable, so the front axle on this Patrol can't go back to the original spring-under layout unless I sourced an entire front axle housing; which is one of the primary reasons why I decided to go ahead and invest the time to convert the rear, and re-do the front conversion safely. The other reason being that this Patrol may still end up back on Ebay some day, and let's face it- tall, aggressive 4x4's with big fat wheels and tires attract a larger potential buyer base than stock height ones do This Patrol was never a restoration candidate since none of the serial numbers match up, so I might as well make it look and perform like it is ready for Moab...

If the front axle had been able to go back to the stock SUA design, I might have gone that route, since it would have entailed a lot less time measuring, calculating, and fabricating...

Regarding lift:

When you do an SOA, the final amount of lift gained (measured as the increase in distance between the frame rail and the ground) is the sum of the thickness of the spring pack, plus the height of the spring perch as it sits on top of the axle, plus the diameter of the axle tube - All of this is assuming that you are re-using the same springs on top of the axle that were originally below the axle.

So, when someone throws out generic lift gains like 5 inches, 6 inches, etc, they are not taking into account that different vehicles have spring packs of varying thicknesses. Because the Patrol has such a thin spring pack, the maximum lift you can expect to gain from this conversion, when using stock patrol springs, is going to be about 4 to 4.25 inches MAX.

The final lift height can also be affected by adding/removing leafs from the spring pack, or changing to a spring with less arch, changing shackle length, etc...

For my application, I am not re-using the same leaf springs- I am going to use the flatter springs from my other Patrol, so I will yield the axle tube width (2.75 inches) plus the width of the spring pack (1.75 inches), plus height of the spring pad (3/4 inch stock, but I will grind the arches in my spring pads down so that they only add 1/2") MINUS the difference in the arch between the original springs and the springs I am swapping to (which was a full 1.5 inches difference)... This should net out to about 3.5 inches of lift over the original rear height, and should result in the rear sitting about 1/4" higher than the front currently sits with the hard top removed- so that adding a hard top would bring the front and rear perfectly level.

Now, regarding the pinion angle - Faux40 is correct that the trick to eliminating vibration is to make sure the output from the t-case is parallel to the angle of the pinion, WHEN THE DRIVETRAIN IS UNDER LOAD. Leaf springs (especially soft, well worn 50 year old ones) always deflect some small amount when the torque of the drivetrain is applied (also called spring wrap), and this torque-twist effect raises (increases) the pinion angle slightly; so the trick is to set the pinion at an initial angle that allows for this small twist-effect to occur, and nets out to the target zero degree difference between the two U-joint angles when you're blasting down the highway.

Since the exact amount of spring wrap is a variable that can't really be determined up front, I use a very old-school hot-rodder's method for establishing the correct initial pinion angle... I apply all my experience, combined with my best judgement about how much "give" the springs will allow, versus how much torque the engine will actually apply against them... and then take a wild-ass guess as to how much spring wrap to factor in, and hope I turn out right.

For this project, I'm going to guess that the springs are going to allow about 2 degrees of pinion deflection, yielding 7-8 degree total pinion angle. If I'm wrong, then the spring pads will come back off, I'll tweak the angle a little bit, and try it again.

For some things, good old trial and error are still the best guides to (eventual) success

You guys are correct that a double cardon CV joint GREATLY simplifies the need to get this driveline alignment perfect, and If I can't get this one vibration- free without a custom drivehaft, then I'll cross that bridge when I get there.

Awesome stuff. Thanks for sharing.

If you are only netting 3.5", you should be OK. My old 75 CJ5 had 12-leaf packs on each corner. It had the old narrow springs with add-a-leafs added as they began to sag. I bought it wrecked. The springs really needed to be swapped out.