JeepcoMJ Posted April 2, 2009 Share Posted April 2, 2009 87 SWB comanche. np231 with SYE, 6.5" lift with aw4 trans and 4.0 HO conversion. bent my rear driveshaft the other day playin on the rocks with 89eliminator. took it off so I can drive in FWD to work tomorrow since the company van has now fried all of it's electricals (bad body to motor ground strap, I think...clears everything, starter won't turn over, engine won't run when it does turn over). anyways. here's the plan. have the rear driveshaft retubed...but made to the length of a front aw4 driveshaft. get the proper carrier bearing and have an intermediate shaft built. this shaft will go from the t-case, through the carrier bearing, and have the proper yoke on the back of it to allow me to bolt my double cardan rear driveshaft to it. build a crossmember at the proper position, which sits between the frame and flush mounts. at the same time build a trans crossmember which sits between the rails too. this will allow for one very nice belly skid between the trans and that crossmember...giving me t-case protection. it will also allow me to have both driveshafts at the same length. the rear driveshaft currently uses a thicker tube than the front, and so it will remain my dedicated rear driveshaft. it's also currently a double cardan driveshaft. so, the goals: uniform driveshaft length allowing me to carry one spare driveshaft. zero parts hanging down, full belly protection. less chance of contacting the driveshaft on rocks due to a slightly steeper DS angle. does anyone have any input on this? It's only a concept at the moment, but I really think it can work. -Pat Link to comment Share on other sites More sharing options...
Pete M Posted April 2, 2009 Share Posted April 2, 2009 I've thought about that too. Mostly because it'd give more ground clearance. But I'm not going to do it until I can get a Hi-9 diff in the back. :D Matching your front driveshaft is a great idea. I hadn't thought of that. :thumbsup: Link to comment Share on other sites More sharing options...
JeepcoMJ Posted April 2, 2009 Author Share Posted April 2, 2009 I've thought about that too. Mostly because it'd give more ground clearance. But I'm not going to do it until I can get a Hi-9 diff in the back. :DMatching your front driveshaft is a great idea. I hadn't thought of that. :thumbsup: thanks. figured a flat belly and more ground clearance would work out great for me. besides, I'm not increasing the driveshaft angle THAT much, I'm retaining the double cardan, and the intermediate shaft will be set up in a way that I won't have to change the pinion angle as well :D Link to comment Share on other sites More sharing options...
mvusse Posted April 2, 2009 Share Posted April 2, 2009 With your current set up, to prevent drive shaft vibrations your pinion angle should be parallel to your transfer case output. Or at least close. This will point the pinion to where? About the front bumper? With a double cardan drive shaft the pinion u joint should be straight in line with the drive shaft, or pointing to a few inches behind where your carrier bearing is going to be. How can you think that is about the same pinion angle? Good idea, though, but don't think you're not going to have to move your perches. And you'd have to point the truck downhill to be able to fill the rear diff with enough oil, or make another fill plug higher up on the cover. Link to comment Share on other sites More sharing options...
Eagle Posted April 2, 2009 Share Posted April 2, 2009 I think you have to re-think the pinion angle. A double cardan has two u-joints in it, so it is self-cancelling for phase. The other end of the shaft is a third u-joint, which has to run at essentially zero angle to avoid out-of-phase vibrations and harmonics. Link to comment Share on other sites More sharing options...
james750 Posted April 2, 2009 Share Posted April 2, 2009 I agree that keeping the axle side pinion angle at zero will stop driveline vibrations, but if it is at zero there will be end galling problems as well as reduced u joint life. Link to comment Share on other sites More sharing options...
Eagle Posted April 2, 2009 Share Posted April 2, 2009 I agree that keeping the axle side pinion angle at zero will stop driveline vibrations, but if it is at zero there will be end galling problems as well as reduced u joint life. How? Why? Please explain. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted April 2, 2009 Author Share Posted April 2, 2009 umm. I already have SYE and already have double cardan shaft. will mount carrier bearing with flange set to make the straight part of the double cardan shaft in line with the pinion (actually, a couple degrees UP so that when I accelerate, it carries down and in-line with the shaft). so, since I already have a double cardan rear shaft, this will work out as I stated earlier. trust me, I've already done the geometry. Link to comment Share on other sites More sharing options...
Automan2164 Posted April 2, 2009 Share Posted April 2, 2009 There has to be at least 1 deg of ds angles, because without that small amount of difference, the bearings won't rotate enough in the caps, leading to wear spots and reduced life. A zero angle wouldnt keep the bearings moving unless you are constantly cycling the suspension and changing the angle. Rob L. Link to comment Share on other sites More sharing options...
james750 Posted April 2, 2009 Share Posted April 2, 2009 I agree that keeping the axle side pinion angle at zero will stop driveline vibrations, but if it is at zero there will be end galling problems as well as reduced u joint life. How? Why? Please explain. Because if the end caps/needle bearings do not rotate on the joint then they will just sit in one spot all the time. This will wear groves (end galling) into the joint and cause the bearings to get caught up when the bearings finally do need to move when flexing or when the rear axle is pushed up causing a greater angle than zero. It does not need to be much of an angle at all, just enough so that the bearings keep moving. EDIT:Automan beat me to it Link to comment Share on other sites More sharing options...
Automan2164 Posted April 2, 2009 Share Posted April 2, 2009 Lol, sorry to steal your thunder James, Long time member coming back from the abyss here. Just trying to warm up to all you new guys... I kinda helped pete with the switch to the forum from yahoo, and well started chasing girls and a diesel ram. I'm back though, and have a new purchase. Ill post pics and junk after I pick it up on sat. I am the originator of www.comanchemj.1hwy.com . Rob L. Link to comment Share on other sites More sharing options...
500 MJ Posted April 2, 2009 Share Posted April 2, 2009 I thought that you wanted your pinion angle to be a hair lower than what you would actually run as so that when you accelerate the angle would then come up? :hmm: Link to comment Share on other sites More sharing options...
JeepcoMJ Posted April 2, 2009 Author Share Posted April 2, 2009 I thought that you wanted your pinion angle to be a hair lower than what you would actually run as so that when you accelerate the angle would then come up? :hmm: yeah. it's been awhile since I looked at it. that's what I was meaning to say lol. regardless, it's set properly right now. I'll accomdate the carrier bearing height to obtain my goal. Link to comment Share on other sites More sharing options...
500 MJ Posted April 2, 2009 Share Posted April 2, 2009 K - Good, for a sec there I thought I was off my rocker... Link to comment Share on other sites More sharing options...
86FUBAR Posted April 3, 2009 Share Posted April 3, 2009 I am currently trying to get the samething acomplished on my mj but I'm using the rear D-shaft out of a 82 chevy 1ton , the slip yoke off a 91 chevy auto (still havent test fit the yoke but is suposed to work) . if the chevy yoke dosnt work then i gues i will use the stock one but then that means i will have to get a bastard u-joint for the front as well as for the rear , i could get the propper rear yoke but those cost some bucks and i aint got an SYE yet so ... Link to comment Share on other sites More sharing options...
crosbike Posted February 24, 2013 Share Posted February 24, 2013 whatever happened with this? I have been thinking of the same thing. Link to comment Share on other sites More sharing options...
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