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T-case drop?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by kpanza, Dec 20, 2000.

  1. kpanza

    kpanza 1/2 ton status

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    Ok, I just went from a 4" lift to a 6" lift, along with installing my 14 bolt rear this weekend. I now have a pretty bad vibration coming from the drivetrain. I guessed that it was the driveshaft. So, this morning I took it down to a friend at Drivelines Inc. and he told me that the pinion angle was near perfect, but the t-case angle was way off. So, he said that the easiest way to correct this was to lower the t-case with spacers. I have heard of this a lot, but always hear about the problems with it, like the transmission, motor and radiator fan all moving as well, sometimes causing the fan to make unfriendly contact with the radiator! IS this true? I can get some spacers pretty cheap, but is it better to suck it up and get a custom driveshaft, maybe with CV joints to answer the problem? I have a 1987 K5 with a 208... thanks!
     
  2. Emmettology 101

    Emmettology 101 3/4 ton status

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    You can get a t-case drop for free! THere are spcers on you bolts for your t-case right now! They are above the frame. All you have to do is unbolt the t-case and put those spacers between the crossmemeber and the frame!

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; http://emmett.coloradok5.com
     
  3. kpanza

    kpanza 1/2 ton status

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    Ok, yes, I have seen those spacers up there! So how much would that lower the case overall? Just an inch or so? Do you recommend dropping it? What is the max you would drop it? I just want to do the right thing as far as durability and future problems kept to a minimum...
     
  4. ftn96

    ftn96 1/2 ton status

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    I just did this as well, and it did help. But there is still a vibration that is just tolerable for now. I am taking the shim out from under the rear springs Friday adn raising th T-case back up. Hopefully this will help.
    You may need to do the same thing. But try the spacers first.

    I miss my Ex, but my aim is getting better!
    http://mccordhouse.freeservers.com
     
  5. Emmettology 101

    Emmettology 101 3/4 ton status

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    That would drop it about an inch. I wouldn't go anymore than that. I dont have mine dropped, butI also dont have any vibes so far....



    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; http://emmett.coloradok5.com
     
  6. ken

    ken 1/2 ton status

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    Not to disparage your buddy at Drivelines, but the pinion and output angles should be the same...I don't believe there is a "perfect" pinion angle...but rather the idea to stop a shaft from vibrating is to get these two angles THE SAME, whether that involves lowering the transfer or shimming the rear axle. My guess is there is still work to be done with regard to the angle on your rear axle pinion...fix it with shims or whatever, I KNOW that you can get that angle the same as your transfer's output WITHOUT lowering the transfer. Keep at it.

    ken
     
  7. kpanza

    kpanza 1/2 ton status

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    Yeah, I guess that is what I meant as far as the angles being the same...my rear springs came with a shim bolted on, and with the ORD shackle flip, maybe it is too much correction? I think I will take the shim out and see how that goes first...Wade (the owner of Drivelines) noted that my slip yoke uses the high angle type joints, so as long as they are within their operating range, it sounds like it is better to correct the pinion angle to the t-case (instead of the other way around?) Thanks guys for your help - I just want to solve this quickly so that I can get out and really enjoy the holiday weekends!! I can hear that Detroit clicking away, I want to go test it!!! ha,ha What is the easiest way to measure the angles? Use an angle reader on the end of the tailshaft housing and the flat part of the pinion yoke?
     
  8. ken

    ken 1/2 ton status

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    I was just reading your original post again...think about it, how does the angle of the rear output of your transfer case get "way off"??? It is in its stock location, right? Naw, you've changed the pinion angle extremely by doing the shackle flip, and that is exactly where you should be addressing the angularity problem...REAR AXLE!!!

    ken
     
  9. ken

    ken 1/2 ton status

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    Oh my gawd!!! You haven't measured your angles yet?!?! Ya gotta know that first!! Go to Harbor Freight and buy their $4 angle finder and git to measuring!!! I'll guarantee that your transfer angle is probably something on the order of 5-8 degrees, whereas your driveshaft is probably more like 10-14 degrees. NOT GOOD!! Get em the same or you'll be vibrating away, which not only is hard on u-joints but will take out pinion bearings and transfer case output bearings if left to vibrate away too long!!

    ken
     
  10. kpanza

    kpanza 1/2 ton status

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    Ok Ken, where is Harbor Freight? I work n Irvine (by the Airport), is it anywhere close? Now that we have narrowed it down to the rear axle, should I take the shim out, reverse the shim, or just cut off the perches and weld on at the correct angle? Well, that is, AFTER I get my angle finder and know what the angles are!! :)
     
  11. ken

    ken 1/2 ton status

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    The closest HF to you is on Tustin AVenue, at the 22 freeway. From Irvine, take 55 fwy N to 17th, turn left on 17th, turn right on Tustin and its up about a half mile. Also check out HF's website, www.harborfreight.com/. Unbelieveable that you don't know of HF...it is a big gearhead's toy store!!! Anyways, you are on the right track with suggesting you reverse the shim in the rear spring pack. First though, take a measurement and figure how much reversing the shim will get you. If say, its a 3 degree shim, by reversing it you will gain 6 degrees of downward pinion angle, which is probably what you need. That may be the only thing you have to do to get rid of the vibe.

    ken
     
  12. kpanza

    kpanza 1/2 ton status

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    Thank you Ken!!!! I hope that you are right!! :) Yeah, I found the Tustin Ave store on Yahoo, but I have never been in there! So are you saying that I need to leave my credit cards at work when I go in there?? ha,ha Can you tell me EXACTLY the correct way to measure the t-case angle and pinion angle?? As in, where on t-case (end of tailshaft housing?) and pinion (yoke?).... Thanks Ken, I will definitely owe you a couple cold ones after all your answers!!!

    Keith
     
  13. ken

    ken 1/2 ton status

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    Definitely leave your credit cards at home or work before you get to HF, otherwise you'll be like me and spend over $100 everytime you go in there!! As to measuring, take your angle finder and hold it up to the yoke on the 14 bolt (you'll probably need to disconnect the d/shaft to get an accurate reading) on the flat surfaces where the straps that retain the driveshaft u-joint bolt to. You'll be viewing the AF from the side to see at what angle your pinion is pointing upwards...in your case probably 10-14 degrees. Then take your AF and hold it on the output of the transfer case, since you have a slip joint, hold it on the round part where the rear seal goes, and note the angle (s/b about 5-8 degrees). Your shim in the rear axle is most probably 3 degrees, so unbolt your spring u bolts, loosen the center bolt and tap the shim around 180 degrees so that it is backwards and give it a try. That is, if the measurements you take and calculations you make indicate that your angles will be close by reversing the shim. If not, its cut and weld perch time, or drop TC time!!

    ken
     
  14. kpanza

    kpanza 1/2 ton status

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    Ok, so basically if the two angles are within about 6 degrees or so (assuming of course that the shim is a 3 degree shim), I will be fine with turning the shim around backwards? If the difference is more than that, then I need to cut and weld to make up the difference? Now, if I have to cut and weld, is it better to get rid of the shim all together and weld the perches on to make up the total difference?

    Now, there has never been a mention here of a dual cv driveshaft - is it because that is not possible or because it is so expensive? Just asking so that I know (of course I would rather save money and solve it that way)!
     
  15. ken

    ken 1/2 ton status

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    Yes, as long as when you turn the shim around, the angles are exact, or say within a degree. If you have to cut off the perches and reweld them on at a different angle then by all means get rid of the shims.

    A CV shaft is something you may consider if, after getting the angles correct, you still have vibration. I don't imagine you will though, as my Suburban is lifted 13" and uses a standard driveshaft...so extrapolating, you have less wheelbase/driveshaft length, but are lifted 7" less, so you "should" be allright. A dual CV shaft is a specialty item used when you cannot move the angles (by cutting or shimming), you will not need one, at best you will need a single CV shaft, which has the CV on the transfer case side. If used, you then angle you rear pinion to point directly at the transfer case, so that the angle of the u jont at the pinion is zero, or in some cases if you have slight axle wrap, 1-2 degrees downward angle. A CV shaft is a whole different ballgame in terms of your rear pinion angle. I recommend just getting your angles equal and try to utilize your present driveshaft.

    ken
     
  16. kpanza

    kpanza 1/2 ton status

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    Thanks Ken. I just got back from Harbor Freight! You were right! I bought my angle finder PLUS three other items!! ha,ha Decided that my old torque wrench was time to throw away, cause I hate it when it slips just as I am getting all 150 lb ft of torque on it!! And a new grease gun is nice to have, one for the garage, one for the trail... ha,ha And I was only there for 5 Minutes!!!! Just imagine if I had actually had time to look around on my leisure!!! I will measure the angles tonight, see what I can do...
     
  17. HarryH3

    HarryH3 1 ton status Author

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    The combination of the shim on the springs and the flip kit has probably tilted the pinion up way too far. The flip kit tilts it up a few degrees and then the shim tilts it even more. That has made the angle far too different than the angle up at the t-case. Let us know how big the difference between the two is!

    <font color=black>HarryH3 - '75 K5</font color=black>
    http://ThunderTruck.ColoradoK5.com
     
  18. kpanza

    kpanza 1/2 ton status

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    Ok, will do! I will try to take measurements of everything and let you guys know, maybe we can help someone else when they do this kind of lift...just kind of a total bummer when you get everything hooked up and looking great, then you can't drive it for fear of throwing another driveshaft away!! Thanks for everyone's help, it really is great to be part of this community of K5ers!!!!!
     
  19. kpanza

    kpanza 1/2 ton status

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    Ok, one more question I remembered I wanted to ask: Can anyone tell me why they think the vibration is so much worse when I let off the gas? I mean, I can definitely feel vibration at all speeds, and accelerating, but it is especially bad when I let off the loud pedal or coast to a stop... does this have to do with the springs being "loaded up" on power application and then "releasing energy" upon letting off the gas?? I'm shooting in the dark on that one, thought I heard that before...
     
  20. ken

    ken 1/2 ton status

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    That's because when you let off the gas the driveshaft and running gears are not under load. When on the freeway, try the neutral throttle thing when coasting...not on the gas, not really off the gas, kinda in the middle...thats when things REALLY vibrate!!!

    ken
     

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