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Driveshaft is too short for a 4" lift?

Discussion in 'The Garage' started by guido666, Oct 19, 2005.

  1. guido666

    guido666 1/2 ton status

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    I just installed a 14bFF and 4" blocks (I have a shackle flip, but that will wait until spring). While reconnecting the drive shaft with the truck still up on jackstands, I noticed that at full droop, the drive shaft is all the way extended, maybe more. Anyone else experience this problem? Is there a simple way (another truck) to get a slightly longer driveshaft without going custom?

    Which will break first, whatever stopping mechanism seems to be built into the shaft, or the u-joint at either end.

    Oh, '79 Blazer.
     
  2. 350k5

    350k5 1/2 ton status

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    If I recall correctly you should be ok running the stock shaft with only a 4" lift. I belive that once you get into 6" or more you should start looking into a new shaft. If your worried about breakage just pick up some cheepo U-Joints, thats your best bet in making sure they are the weakest link in the setup. Plus with some cheep ones you can always have a few replacements with you on hand. Works out well.
     
  3. mini_mull

    mini_mull 1/2 ton status

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    You can just have it lengthened without getting a whole new one. Not sure how much that costs, though. Trucks and Burbs are usually fine, but from what I remember on other posts some need it lengthened with 4" lift, so you might, too.
     
  4. YZEATER

    YZEATER 1/2 ton status

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    what stops the driveshaft from coming apart? i have one i wanted to pull apart and it wouldn't.
     
  5. guido666

    guido666 1/2 ton status

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    That's what I was asking as well. I was wondering if it was some kind of strong stop like a bolt, or just a c-clip or ridge.
     
  6. 350k5

    350k5 1/2 ton status

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    Well yea, but just think that the driveshaft is under an unbeleviable ammount of torque and strees. It has to kind of hold everything together between two large stress factors. I don'k know if you are supposed to be able to take it apart - that would just make the whole assembly weaker. At least I would think. :o
     
  7. guido666

    guido666 1/2 ton status

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    It wouldn't make it weaker really. It's just the same as a slip yoke, just in the middle of the shaft. Whatever locks it together is just to keep it from pulling all the way apart. But it can't be too strong a hold.
     
  8. Zeus33rd

    Zeus33rd Smarter than you GMOTM Winner

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    There is nothing really holding the the two pieces of a shaft together. Maybe a little plastic nut thing, or the rubber boot held on with zip ties. If your suspension will droop far enough and the shaft isn't long enough, it'll just pull apart. Check out this picture-
    [​IMG]

    This is my old junkyard front shaft with 52" front srpings. It only had about 4" of splines....That wasn't enough to stay together with soft, flexy springs, so it pulled apart. I've got a High Angle Drivelines shaft now with 14" of slip, so I don't worry about it anymore. :D

    As far as your rear shaft goes, when you say "all the way extended" what do you mean? How much spline is still inside the slip? With it all bolted up, at full droop on the jack stands...can you see splines? A rear shaft doesn't really slip all that much, a front shaft slips ALOT on the splines in comparison. In my opinion, I wouldn't worry to much if you can see alittle bit of splines at full droop. It doesn't sound like you truck is trail only or has super flexy suspension, so as long as you don't plan to jump your truck, or ever get both rear wheels off the ground at the same time, your shaft should work fine.
     
  9. Cornfield creations

    Cornfield creations 1/2 ton status

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    I run the stock driveshaft on my 79 k-5 with 4" springs, works alright, I got some vibration, but I am saving up for a high angle driveline cv shaft to take care of those :D
     
  10. guido666

    guido666 1/2 ton status

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    By "the shaft is all the way extended" I mean that when I had the truck up on jackstands (and the rear axle was at full static gravity droop) I could not extend the driveshaft long enough for the u-joint to mate with the yoke. Once I put the truck back on the suspension the compression of the springs allowed me to bolt it up.

    I don't remember being able to see any splines showing, they stay within the rubber seal that is over them. Again, only as I remember it, they may come out.

    The only changes I've made is installation of 4" lift blocks and a 14bFF, and putting a conversion u-joint (1310-to-1350) on the end of the driveshaft until I can afford a custom shaft.

    As you pointed out, at this point I'm not going all crazy off-road. YET. I'm just waiting until I get it all done. I finished putting a 454 I built up in it, and now I've got my rear axle and tires. Next (this week) I'm finishing building a 3/4 ton front end and that will go on (with 4" lift springs). Some people build these up so they can drive down the street and look cool, I am honestly building it up so that when the road ends I make my own. :-)

    How much does a nice shaft like yours run? And I keep hearing about 52" springs. What are these off of? How long are my stock springs ('79 Blazer)? What benefit do you get from these (longer?) springs?
     
  11. sandawgk5

    sandawgk5 3/4 ton status

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    I maybe wrong but the rear axle will sledom see full droop in the centerline unless you jump it. With flexing on side or the other the driveshaft moves only a fraction of what the tire moves. On the front it is a different story due to the pinioin being closer to one side than the other so when the passenger side tire moves up or down the front shaft sees almost the same amount of movement. Measure the shaft fully extended, put your truck on the ground and hook up the drive shaft and measure it again that will tell you how much slip you have inside the shaft. I think you will be fine.

    Ira
     
  12. guido666

    guido666 1/2 ton status

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    Ok. Good point.

    Any answers to the questions about the springs or the driveshaft cost?
     
  13. sandawgk5

    sandawgk5 3/4 ton status

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    I am not sure on the shafts give Jess a call at High Angle Drivelines and he will give you a quote. They aint cheap but then again you wont have to buy another shaft again. As far as springs your rear springs are 52" long. What people are reffering to is putting the 52" rear springs in the front to gain ~4" of lift over stock. The longer springs for the rear are 56" Chevy rear springs ford 57" rear springs or the 88+ chevy truck rears that are 63" or 64". The reasoning behind using a longer spring is the arch that the spring moves through is greater and allows for more droop and a little more compression. With certain springs flipping the springs around will also allow you to push your axles farther apart to stretch your wheel base out.

    The 56" springs can be found on 3/4 and 1 ton Chevy trucks and 3/4 ton Suburbans from 73-87 and some 1/2 Suburbans. The 64" springs are on 88+ Chevy trucks. The 57" springs are from a Ford Bronco but only certain years measure the springs width some are 3" wide and others are 2.5" wide unless you want to grind spring steel you want the 2.5" wide ones. The best place to find any or all of these springs is your local salvage yard.

    Ira
     
  14. guido666

    guido666 1/2 ton status

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    Just so I am understanding, my stock rear springs are 52" and the front are shorter. In order to get more flex, you get 52" rears and put them in the front. (Not sure how that gives extra lift as well, are they more arched?) So in order to make the rear match, you get longer springs for that as well (the 56"/57"/63"/64" you mentioned). Am I understanding correctly?

    Are these springs arched more naturally, or does the art of cramming bigger springs in a small gap force them arched? Or do you move the mounts to compensate?
     
  15. sandawgk5

    sandawgk5 3/4 ton status

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    Your front springs when stock are about 49" long I think and they have a negative arch. They look like frown when viewing from the side. This was done to soften the ride of the leaf spring suspension to my knowledge. The 52" springs have a positive arch that is equivalent to a 4" lift front spring. And yes your Blazer has 52" springs in the rear. You can not just bolt 52" springs in the front. You have to move the front spring hanger forward atleast 2" preferably 4". Also several people move the shackle mount for the front spring forward to improve shackle angle. Also due to the extra flex from the springs crossover is a necesitty. To put 56's on the rear just swap sides with shackle flip of your choice and the 56s will bolt right in and keep the axle in the stock location if you install them with the short side forward. You do not have to put longer springs in the rear however most people do because they use their rear 52s for the front. I have plans to put 56" springs front and rear in my truck. No paticular reason other than I like the uniformity of it, plus I think it is kewl and it allows you to push the axles farther apart. I would like to have between 116-120 wheelbase.


    Ira
     
  16. guido666

    guido666 1/2 ton status

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    I know everyone has different ideas of what the ideal 4x4 is, but what is your reasoning for wanting that extra 10" of wheelbase? (Sorry for all these questions, I'm fairly technically proficient meaning I've managed to build up a strong engine and axles and install them myself, but I'm new to the world and lingo of full-size Chevy 4x4s.)
     
  17. sandawgk5

    sandawgk5 3/4 ton status

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    I plan on running a double and a flat belly so the extra wheel base will relieve some of the driveshaft woes. Also pushing the axles out will help with approach and departure angles. I might suffer on breakover angle but with a flat belly I should just slide right over. I have all these plans and no where near enough money :doah: I don't really do mud mainly rocks and I intend to retire around the Flagstaff area it seems pretty central to a lot of rock crawling areas and it is a helluva lot cheaper than here.

    Oh and no problem with the questions. You can't learn if you don't ask.

    Ira
     
  18. guido666

    guido666 1/2 ton status

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    I assume you are referring to a doubled transfer case, and some kind of rotating kit to make it not stick down any more?
     
  19. sandawgk5

    sandawgk5 3/4 ton status

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    You would be correct. When it is all said and done I will have a 203/205 doubler and there will be a steel plate mounted to the frame rails and the drivetrain will be between the body and the plate. Esteban86K5 has some pictures in his gallery of his flat belly.

    Ira
     
  20. guido666

    guido666 1/2 ton status

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    That is simply awesome. How does this work? Won't tipping the transfer case cause it to lube improperly? How do you modify the shifters to work with this? Is this the same thing as a "clocking ring" (I think that's what I heard it called)?
     

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