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Pjc360

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Discussion starter · #1 ·
I have a 1991 dodge power ram 150 short bed 4x4 truck. It has an A-518 auto transmission and a np241 transfer case. 4 inch rough country lift springs on the front and a tapered 4 inch block stacked on top of the factory block on the rear.
The u-joint on my rear driveshaft at the transfer case gets destroyed super fast no matter what brand the u-joint is.
I bought an angle finder and removed the rear driveshaft and measured he angle at the yokes. The yoke at my transfer case is 85 degrees and the yoke at my rear pinion is 79 degrees. That's a 6 degree difference, is this why my u-joint at the transfer case gets trashed so quickly? And if so what can I do about it?
I don't want to use shims on the rear axle because I already have two stacked blocks. I don't want to stack something else in that mess and I plan to eliminate the rear blocks all together and put rear lift springs on the truck when I get the money.
For now I need to figure something out to get that angle to where a u-joint will survive more then a few days, I was thinking about dropping the back lift down and see if that will help, it should bring the transfer case down a little bit closer to the rear pinion angle.
I have some 3 inch blocks I can put in place of the 3.5 blocks I have on the truck now, I hav 3.5 factory blocks on bottom and a 4 inch tapered block on top of it.
I found some 3 inch blocks and I could put them on the bottom to drop the rear lift down a 1/2, that should do something for the angle right?
I need suggestions please.
 
#2 ·
http://www.pirate4x4.com/forum/general-4x4-discussion/585932-max-driveshaft-angle.html


Says here less than 5 degees is optimal. I would get rid of your double stacked blocks, shit way of lifting anyway since axle wrap my be the root of your problem, and get a 4 inch lift SPRING set. The further away your axle is from the springs the more leverage the torque of driving has. Thus rotating your axle which could be causing your issue. If you are rock crawling or off roading in hard terrain then I would also add an 'anit-wrap' bar. Do your research and find out what is best for you.

I rock crawl a 2000 1500 ram, 5 inch lift springs, with a dana60 and kept my factory blocks in and I get tons of axle wrap. I'm also rocking 4.56 gears and 37s. Taller tires don't help either.
 
Discussion starter · #3 ·
Yes I know stacked blocks isn't he best way to lift the rear, I have been slowly building this truck and I will get rid of the blocks for rear lift springs, in fact I'm going to install a brand new all spring 4 inch lift on it because I hate how rough the rough country springs are.
I'm going to get skyjacker or tuff country, haven't made up my mind which for sure but I'm leaning towards skyjacker.
So in the mean time my best option is to go ahead and lower the rear a little bit and seeing what that does right? I mean if I lower it a 1/2 inch it should bring the angles closer.
If lowering it a 1/2 inch doesn't get the angles close enough I will lower it an inch and see what that does because right now the rear of the truck sits an inch and a half higher then the front so if I had to drop an inch it would still be 1/2 inch higher in the back.
I will go ahead and try lowering it 1/2 an inch and see what that does, I need to figure out something to keep u-joints alive and happy right now and in the near future I will get a brand new lift for it and then I can use shims to get the angle closer if need be.
 
Discussion starter · #4 · (Edited)
The angle of my transfer case yoke being 85 degrees and the angle of my rear pinion yoke being 79 is too much difference to keep the u-joint at the transfer case happy correct? I mean that's a 6 degree difference.
I'm just trying to make sure that's why my u-joint at the transfer case is failing so quickly. I realize axle wrap could also be contributing.
 
Discussion starter · #6 ·
Within 2 days though? I know plenty of other people who run and have run stacked blocks on these old dodges and didn't have the problem I'm having. I beloev axle wrap could be contributing to it but I don't believe it's the sole issue and that there is an angle issue and that the angle issue is the major cause.
Literally I can put new u-joints in the rear driveshaft and its butter smooth for about 2 days then it's back to vibrating when accelerating and a constant vibration when crushing down the highway at 65.
 
#8 ·
4 1/2" Rough Country lift on my '92 Ramcharger, for comparison. COMPLETELY re-did my driveshaft - got rid of the slip yoke, by going with a Ford-style flange attachment and a double cardon. 1350 connection at the transfer case - 7290 at the axle! And it was STILL binding.

Shimmed the rear axle with 8 degree steel shims - shimmed it PERFECTLY. Lemmee know if you want pictures.
 
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#10 · (Edited)
Should be the 7290's. You can't get much angle out of them. I used to go through one a day on my 85's front drive shaft. Switched to a Spicer and they would last through the weekend. Finally switched to 1410's about 4 yrs ago and have had no failures since. I also have a 4" lift and 35's.
 
Discussion starter · #12 ·
Yea I know running a cv would solve it, but I can't afford a brand new cv driveshaft right now, that would run me at least 500 if not more.
Right now I'm just tryin to figure something out that will work without having to spend a lot of money untill I can get the money I need for rear lift springs.
Looks like my cheapest option is going to be dropping the back lift down and seeing if that will get the angle a little closer.
 
#13 · (Edited)
6 degrees shouldn't be that big of a deal, especially if you've only been on the street so far. You can try dropping the tcase some (there used to be a kit for this, if not you can make one) to help the angle but I'd lean more towards bent or out of balance drive shaft first, or maybe the slip is binding. My next culprit would be axle wrap. Your engine and transmission mounts could also be bad allowing flex in the driveline.

Duane
 
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Discussion starter · #15 ·
Driveshaft is not bent or out of balance. I took it to a driveshaft shop and he balanced it and put new u-joints in it and it is in phase. Like I said when I first put it on it was butter smooth for about 2 days. Then the vibration slowly started coming back.
Transmission mounts are brand new, I installed them myself and they don't even have 5 thousand miles on them.
The u-bolts are brand new and they don't even have 5 thousand miles on them ether and they are tight I have verified that several times. One thing a friend mentioned to me was maybe the bearing on the transfer case is wiped out causing the u-joint to become wiped out too. But if that were the case why would it feel perfect with new u-joints in it for the first couple of days and then slowly start vibrating again?
 
#17 ·
I think the min thing you need to think about is that there are literally thousands of 1/2 Dodge trucks with 4" lift kits on them not having this issue. So what makes the others different from yours? Not all of them have Double Cardan drive shafts or other similar modifications and many of them also are running the ill-advised stacked blocks. With that in mind, I would start looking for worn and/or damaged parts that would make your setup different from everyone else's that seems to not have your problem.

You say the shaft is balanced and in phase, but is it the right length? Could it be bottoming out and destroying the joint?

If the driveshaft checks out, then I would move on to the yokes. Detroit yokes are made of dog shit and wear really easily which can cause the joints to move around and spit out a cap. Old, worn yoke straps can also cause the same issues. The joint should fit the yoke tight with no, repeat, no movement in any direction. When replacing Detroit joints, I will typically put the C-clips on the caps and test fit them in the transfer case and axle yoke to see if replacing the joints is even worth the effort.

You say the U-bolts are tight but how tight? Were they torqued to spec? The spec for a 9 1/4" is 65 ft lbs minimum. I personally prefer a bit more, but you have to be careful not to crush the tube, which is very possible with an old housing with some rust under the spring plates. With stacked blocks, U-bolt torque is critical to keep them from shifting. Are the springs installed correctly? Block lifts do not require the stock springs to come out, but anything is possible and a cocked axle due to a reversed spring is not unheard of.

Similarly to the cocked axle, the engine and transmission can be similarly cocked up due to the mounts not being replaced correctly. Any side to side angle will add to the angle the joint sees. The driveshaft does not care about up and down and has no concept of the term level. All it knows is the relation of one yoke to the other. We tend to think of driveshaft angle in relation to the slope of the driveshaft, but you could have a perfectly level driveshaft with one yoke 3' to the left of the other and it be the same as them being inline and there being a 3' drop between the transfer case and axle. The point is all the angles add up. You may only have a few degrees difference measured vertically, but if the axle or drivetrain is cocked to one side, that will add to the angle and potentially make it more extreme than it first appears. So make sure of the angles on all planes.

Additionally, it's good to see how things are operating and how the various forces are acting on the drivetrain and suspension. Have someone you trust drive the truck past you laying on the ground watching the driveshaft, axle and suspension. Have them launch it hard right beside you so you can see how the weight transfers and how the axle is moving under all the force and stress. Look for the axle shifting forward before the truck begins to move. Look for any sort of jumping or shifting. Look at the same from behind the truck. Hell, if you have something like a GoPro, film it as you go wheeling or driving around. You are closer to your truck than we are so it's going to be up to you to see what makes your truck the oddball that eats joints.

By the way, the stock rear shaft joints for just about any Dodge 1/2 ton from the '60s on up to at least the swap to AAM axles was the Detroit 7260, not the 7290. The 7290 series was used on some 3/4 and 1 ton trucks but I've found Spicers to be just as common on them. At any rate, the 7260 is a light joint used on cars as well as 1/2 tons and are almost as crappy as their yokes.
 
Discussion starter · #19 · (Edited)
Elwinel, I have checked both yokes. I measured them with digital calipers, measured at the ears and they are fine. I don't see or feel any thing on the yokes.
The owner at the driveline shop said this driveline is in perfect condition, it balanced beautifully and its in phase and I put brand new u-joints in it for you.
He said the splines are good, the mounting surfaces are good and it's straight.
He said there is nothing wrong with this driveline.m
I told him what is happening to me and he asked if it has any kind of suspension lift and I said yes and he said there ya go its 90 percent likely there is an angle problem.
The u-bolts are tighter then 65 ft lbs, I torqued them to 80 ft lbs.
I really don't know what is causing this if it is not an angle issue. If 6 degree difference between the two yokes is acceptable then I truly have no idea what's causing this unless the bearing on my t-case is out. I just don't see why it would feel butter smooth for the first couple of days with new u-joints if the bearing on the t-case is out, you'd think that would be something you felt constantly.
I'm not trying to be a pain in the ass here I'm just trying to figure out what this is, I can go ahead and lower the back lift down a 1/2 inch and see what happens. I just wanted to ask if a 6 degree difference in angle between the two yokes could be enough to cause a problem before I went ahead and did the work to lower it a 1/2 inch.
 
Discussion starter · #20 ·
It's not the driveshaft, it's not the yokes. It's not transmission mounts ether.Those are three things I have ruled out.
Possible culprits are axle wrap of course but not likely to wipe out a u-joint in 2 days imo anyways, angle issues, or bad bearing at transfer case.
So the angle at the transfer case being 85 and the angle at the rear pinion being 79 a 6 degree difference is not that cause of my u-joint at the transfer case failing quickly?
I mean I'm not breaking the u-joint at the transfer case, but it becomes loose super quick and stays that way untill I replace it. And it causes a horrible vibration at high way speeds.
 
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