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Rear Driveshaft... how far is too far?

Discussion in 'The Garage' started by Vetteman61, Jan 23, 2007.

  1. Vetteman61

    Vetteman61 Registered Member

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    After my 4 inch lift, my rear drive shaft appears to be too short. How far should it slide into the transmission and still be safe? It seems to be sticking out about 3 or 4 inches further than stock. I'd like to get away without lengthening it, but I'd much rather be safe than sorry.
     
  2. Chrisblazzer89

    Chrisblazzer89 1/2 ton status

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    Pics. and truck info would help.
     
  3. goldwing2000

    goldwing2000 Guest

    Shimming the axle would be cheaper than lengthening the shaft, and would accomplish the same result. Plus it would decrease your pinion/u-joint angle.
     
  4. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Shimming the axle won't do much at all for the engagement of the driveshaft and it certainly won't make the shaft any longer. :D

    The only thing you can do to correct the problem is have the shaft lengthened. The slip should only have about 1" of travel inward. If the shaft is out too far you will ruin the tail housing bushing and subsequently the t-case.
     
  5. gmc4cw

    gmc4cw 1/2 ton status GMOTM Winner

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    how did you lift the rear? if you used a block then it should have taper built into it. when I did my 6" lift I didn't need to lengthen my shaft. the slip yoke only came out of the tailhousing about an inch. when I went to an 8" lift I had a new shaft made.

    the only way your could be out 3-4 inches more would be if the axle got moved back. did you use new springs and put them in backwards?
     
  6. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Wrong answer, there are many different springs available and also shackle flips and each vehicle is different and also depending on what tranny/t-case combo it could easily move the slip out that far. I did a spring lift and my driveshaft moved outward of the t-case about what his did. I had to have a DS made so i had HAD build me a C/V shaft and then did a SYE.
     
  7. goldwing2000

    goldwing2000 Guest

    Yes it will. :D

    If you rotate the pinion upwards, it will not only decreases your pinion angle but also moves it closer to the t-case output, thereby decreasing the necessary driveshaft length. Simple geometry.

    If one were willing to do some cutting and welding, you could also rotate the axle under the spring perches.

    You're right about the 1"-1.5" sticking out, though.
     
  8. sandawgk5

    sandawgk5 3/4 ton status

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    It works. Changing my pinion angle moved my slip yoke about 2"

    Ira
     
  9. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    IIRC the slip yoke is about 6" long. I think I would want at least a good 2" of engagement. Any less than that and I'd think you'd be sure to slip the shaft out.
     
  10. Vetteman61

    Vetteman61 Registered Member

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    my 4 inch lift

    I used only 4 inch blocks in the rear. My rear end was bad so I also installed a new (to me) 14 bolt limited slip out from under a 79 4X4. My friends actually put the blocks on while I did other things. The truck is at my dad's shop about 30 minutes from here so I won't be able to look at it for about a week. Is it possible they put the blocks on backwards???? I also thought, though I didn't know for sure, that the blocks should have wedge built into them.
    I used springs up front, but as of yet haven't tried to unstick my front driveshaft to see if it will be long enough.
     
  11. goldwing2000

    goldwing2000 Guest

    Yes, the blocks should have a certain degree of wedge built into them (as long as they're good quality blocks) and yes, it's definitely possible that they could be installed backwards.
     
  12. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    As stated they probably do have some angle to them. I have 2.5" lift blocks and I didn't realize they were angled until I installed them in wrong. :doah: The angle wasn't really perceptible until I put a tape measure on them.
     
  13. SkysTheLimit

    SkysTheLimit 1/2 ton status

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    My K5 was originally lifted 4" with angled blocks in the rear and I had to have my DS lengthened a bit. From what I understand, swapping in a 14bolt should eliminate that need due to a longer pinion area than a 10 bolt.
     
  14. Vetteman61

    Vetteman61 Registered Member

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    why why why

    ah yes, also, when I swapped the 14 bolt in, I obviously had to get a crossover ujoint. The yoke for the 14 bolt was SMALLER than my 10 bolt was. Is that normal?
    I'll definitely check my blocks next time I'm with the truck to try to see if the blocks were possibly installed backwards.
     
  15. Avery4jc

    Avery4jc 1 ton status Premium Member GMOTM Winner

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    uhhh nope...the 10b should have an s44 and the 14ff should have a 1350.
     
  16. iwaxmyjimmy

    iwaxmyjimmy College web wheeler Premium Member

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    Oh no, Avery I've got a 1310 yoke do I need to make it a S44?
     
  17. Chrisblazzer89

    Chrisblazzer89 1/2 ton status

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    IS it out as far as mine is? [​IMG]
     
  18. iwaxmyjimmy

    iwaxmyjimmy College web wheeler Premium Member

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    Jack up the rear, so the rear suspension is at full droop, and if the yoke falls out or if your yoke has less than an 1", I'd look into a Tcase drop kit just to net a lil more if you have less than an inch. But you shouldn't need any more length to the rear shaft. If we had T-cases had flanges on the rear like the front output shaft, we could use drive shaft spacers.
     
  19. goldwing2000

    goldwing2000 Guest

    That's just scary, man. :eek1:
     
  20. BizeeB65

    BizeeB65 1/2 ton status

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    x2! silly boys and thier slip yoke outputs....
     

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