desbennett004 Posted March 17, 2017 Share Posted March 17, 2017 Hi Guys, Just swapped the AX15/231 with the Chrysler 8.25 rear end combo into my 89 Comanche last week. It has 6" of lift in the back. My question is, what have you guys done for rear drive shafts? My stock 2wd shaft is around 11" too long, and the shaft I have that came with the transmission is around 11" too short. Complete length needed including slip yoke is about 47.5". I thought I read somewhere that a stock shaft would be pretty close, but that doesn't seem to be the case. I'm planning to get exact measuments and get the stock shaft shortened, but I wanted to double check with you guys before I dropped the $200 to get it done. Anyone have any better ideas? TIA. Sent from my SM-N900W8 using Tapatalk Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 17, 2017 Share Posted March 17, 2017 Your stock 2WD shaft (if original) will be ~4" in diameter, and the inner shaft is encased by a rubber sheath. Over time the rubber decomposes and makes it nearly impossible to balance from the rubber shifting around inside. This happened to mine, and I had to have a new shaft made. Link to comment Share on other sites More sharing options...
desbennett004 Posted March 18, 2017 Author Share Posted March 18, 2017 Yeah it is the original shaft. I guess that makes it difficult to modify also. Is there another vehicle that uses shafts with the same yoke sizes? It's cheaper for me to get one shortened than get one made from scratch. Sent from my SM-N900W8 using Tapatalk Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 18, 2017 Share Posted March 18, 2017 There are plenty of vehicles that use the 1310 series u-joints. Most 70s-90s GM and Ford half-ton pickups used them. Finding a used one the exact length you need won't be easy. You could always look for an MJ 4WD shaft; AFAIK they don't have the rubber sheath. Link to comment Share on other sites More sharing options...
Jeep Driver Posted March 18, 2017 Share Posted March 18, 2017 My shaft cost $225 new, with new Spicer joints. The only thing I supplied was the slip joint and the measurement. By the time you buy one, have it shortened, install new joints..............$225 starts to look like a bargain. Link to comment Share on other sites More sharing options...
desbennett004 Posted March 18, 2017 Author Share Posted March 18, 2017 That's good information, I appreciate it. I was at pick and pull today looking for drive shafts, but the majority of them are damaged from being moved by a forklift. I will call around locally, see if I can get a deal on shortening a Chev driveshaft, seeing as I already have new u-joints ready to go in. Might get lucky. Can't find MJ 4x4 parts around here, so will have to make do with what we can find. Sent from my SM-N900W8 using Tapatalk Link to comment Share on other sites More sharing options...
DirtyComanche Posted March 18, 2017 Share Posted March 18, 2017 I'm assuming that short driveshaft you've got is out of an XJ. You could have it retubed if need be... Link to comment Share on other sites More sharing options...
desbennett004 Posted March 18, 2017 Author Share Posted March 18, 2017 I'm assuming that short driveshaft you've got is out of an XJ. You could have it retubed if need be...Might be the way to go, seeing as I already have it. Might be a little more money than shortening a shaft, but at least I don't have to look for and buy another one. Sent from my SM-N900W8 using Tapatalk Link to comment Share on other sites More sharing options...
Jeep Driver Posted March 18, 2017 Share Posted March 18, 2017 Minimum diameter is 3" at 4', I don't think a shop will retube an XJ shaft. Link to comment Share on other sites More sharing options...
DirtyComanche Posted March 18, 2017 Share Posted March 18, 2017 Minimum diameter is 3" at 4', I don't think a shop will retube an XJ shaft. It will be fine. Don't run it up to 120mph. Pretty certain the shaft in the rear of mine right now is a retubed front, which is even smaller. Well, more like 100% certain, since I had a shop do it. It's even got rock rash on it, no issues. Being .120" wall (the 'heavy' stuff according to anything but off-road driveline shops) it helps. Link to comment Share on other sites More sharing options...
Eagle Posted March 18, 2017 Share Posted March 18, 2017 Hi Guys, Just swapped the AX15/231 with the Chrysler 8.25 rear end combo into my 89 Comanche last week. It has 6" of lift in the back. My question is, what have you guys done for rear drive shafts? My stock 2wd shaft is around 11" too long, and the shaft I have that came with the transmission is around 11" too short. Complete length needed including slip yoke is about 47.5". I thought I read somewhere that a stock shaft would be pretty close, but that doesn't seem to be the case. Did the transmission and transfer case (and the "new" driveshaft) by any chance come from an XJ rather than an MJ? Link to comment Share on other sites More sharing options...
desbennett004 Posted March 18, 2017 Author Share Posted March 18, 2017 Hi Guys, Just swapped the AX15/231 with the Chrysler 8.25 rear end combo into my 89 Comanche last week. It has 6" of lift in the back. My question is, what have you guys done for rear drive shafts? My stock 2wd shaft is around 11" too long, and the shaft I have that came with the transmission is around 11" too short. Complete length needed including slip yoke is about 47.5". I thought I read somewhere that a stock shaft would be pretty close, but that doesn't seem to be the case. Did the transmission and transfer case (and the "new" driveshaft) by any chance come from an XJ rather than an MJ? Yes, it all came from a 98 XJ. Sent from my SM-N900W8 using Tapatalk Link to comment Share on other sites More sharing options...
Eagle Posted March 18, 2017 Share Posted March 18, 2017 You didn't know that the XJ has a shorter wheelbase than even the short-bed MJ? Of course the XJ drive shaft is too short. Link to comment Share on other sites More sharing options...
Jeep Driver Posted March 18, 2017 Share Posted March 18, 2017 http://spicerparts.com/calculators/driveshaft-safe-operating-rpm-calculator Link to comment Share on other sites More sharing options...
Eagle Posted March 18, 2017 Share Posted March 18, 2017 http://spicerparts.com/calculators/driveshaft-safe-operating-rpm-calculator That's a handy little tool. Thanks for posting the link. Link to comment Share on other sites More sharing options...
desbennett004 Posted March 18, 2017 Author Share Posted March 18, 2017 You didn't know that the XJ has a shorter wheelbase than even the short-bed MJ? Of course the XJ drive shaft is too short.Nope, didn't really think about the wheel base being different. Sent from my SM-N900W8 using Tapatalk Link to comment Share on other sites More sharing options...
desbennett004 Posted March 18, 2017 Author Share Posted March 18, 2017 Minimum diameter is 3" at 4', I don't think a shop will retube an XJ shaft. It will be fine. Don't run it up to 120mph. Pretty certain the shaft in the rear of mine right now is a retubed front, which is even smaller. Well, more like 100% certain, since I had a shop do it. It's even got rock rash on it, no issues. Being .120" wall (the 'heavy' stuff according to anything but off-road driveline shops) it helps. Is there an advantage to running a re-tubed front? Or is it part of a SYE? Sent from my SM-N900W8 using Tapatalk Link to comment Share on other sites More sharing options...
DirtyComanche Posted March 18, 2017 Share Posted March 18, 2017 Minimum diameter is 3" at 4', I don't think a shop will retube an XJ shaft. It will be fine. Don't run it up to 120mph. Pretty certain the shaft in the rear of mine right now is a retubed front, which is even smaller. Well, more like 100% certain, since I had a shop do it. It's even got rock rash on it, no issues. Being .120" wall (the 'heavy' stuff according to anything but off-road driveline shops) it helps. Is there an advantage to running a re-tubed front? Or is it part of a SYE? Sent from my SM-N900W8 using Tapatalk You need a 1310 double cardon type joint and a slip shaft with a SYE. Or at least normally you would. I blew up an expensive Tom Woods shaft and got a junkyard front retubed for the replacement as it has a 1310 double cardon and slip shaft on it. Is it the best solution? No. Also mine is a SWB; I would never consider it with a LWB, if anyone with a LWB reads this. The shaft critical speed is well beyond anything I'd ever dare do with the truck. Link to comment Share on other sites More sharing options...
Eagle Posted March 18, 2017 Share Posted March 18, 2017 You need a 1310 double cardon type joint and a slip shaft with a SYE. Or at least normally you would. I blew up an expensive Tom Woods shaft and got a junkyard front retubed for the replacement as it has a 1310 double cardon and slip shaft on it. Is it the best solution? No. Also mine is a SWB; I would never consider it with a LWB, if anyone with a LWB reads this. The shaft critical speed is well beyond anything I'd ever dare do with the truck. Why do you need a double Cardan joint with a SYE? Double Cardans are used when the operating angle exceeds what a single u-joint can handle. It's necessary on the front because the drive shaft is so short. It's not necessary on the rear unless you've got a very tall lift -- and even then I doubt it's necessary with a long-bed MJ. Link to comment Share on other sites More sharing options...
DirtyComanche Posted March 18, 2017 Share Posted March 18, 2017 You need a 1310 double cardon type joint and a slip shaft with a SYE. Or at least normally you would. I blew up an expensive Tom Woods shaft and got a junkyard front retubed for the replacement as it has a 1310 double cardon and slip shaft on it. Is it the best solution? No. Also mine is a SWB; I would never consider it with a LWB, if anyone with a LWB reads this. The shaft critical speed is well beyond anything I'd ever dare do with the truck. Why do you need a double Cardan joint with a SYE? Double Cardans are used when the operating angle exceeds what a single u-joint can handle. It's necessary on the front because the drive shaft is so short. It's not necessary on the rear unless you've got a very tall lift -- and even then I doubt it's necessary with a long-bed MJ. I said 'normally' because every (or damn near) SYE kit out there comes with a yoke/flange for a double cardan joint. You can put a normal single 1310/1350/1410/whatever yoke on if you can find the correct one (I believe I have a couple that work, but no driveshafts that would work with them either way). That said, there is still a huge advantages to the double cardan joint in it allows you to rotate the pinion up a fair whack, thus potentially saving the pinion yoke and driveshaft from damage, also as it keeps 95% or so of the driveshaft mass at a nearly constant velocity you have less likelihood of vibrations AND shaft critical speed is not as big of a factor, and lastly the double cardan assembly is stronger at a like operating angle VS a regular u-joint, and since the u-joint at the pinion is now only operating over a small handful of degrees it is also effectively stronger. The setup has downsides in that it typically costs more money, unless you're welding perches onto the axle you must run shims to correct pinion angle, and it is more complicated and has more wear parts in general. Anyways, going full circle, the 'need' comment came from the fact that 'normally' the SYEs come with the incorrect yoke or flange to run a standard single u-joint. You still need a slip shaft to be built if you go with a different yoke, and IMHO at that point the cost difference of having a double cardan shaft built would be a wash. A more conventional slip yoke and fixed length shaft with single u-joints would be the cheapest, and if somebody is happy with that then that's what they should buy. Link to comment Share on other sites More sharing options...
wildman4x4 Posted March 20, 2017 Share Posted March 20, 2017 The other reason I was always told for the double cardan joint is because then you can run the transfer case and pinion at different angles. You have to set the output angle and pinion angle have to be the same with a single joint shaft. But if you have a double cardan joint the transfer case doesn't have to be tilted downward pointing at the pinion. Or do I have all my driveshaft knowledge wrong? Link to comment Share on other sites More sharing options...
Jeep Driver Posted March 20, 2017 Share Posted March 20, 2017 The other reason I was always told for the double cardan joint is because then you can run the transfer case and pinion at different angles. You have to set the output angle and pinion angle have to be the same with a single joint shaft. But if you have a double cardan joint the transfer case doesn't have to be tilted downward pointing at the pinion. Or do I have all my driveshaft knowledge wrong? http://www.billavista.com/Tech/Articles/Driveshaft_Bible/index.html Link to comment Share on other sites More sharing options...
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