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rebuilding 205, shims on the idler shaft?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by fortcollinsram, Sep 19, 2002.

  1. fortcollinsram

    fortcollinsram 1/2 ton status

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    Well I have all the parts cleaned and and ready to install...But I can't remember for the life of mee where the really thin shims go on the idler gear assembly...I believe that the go between the forward most bearing and the case, correct? But I can't remember...Also, any tricks to getting all the crap in there...

    Thanks

    Chris
     
  2. m j

    m j 1/2 ton status

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    hit Leadfoot up for tips.
     
  3. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    You are correct in the placing of the shims. They go between the front bearing and the case. I had a hard time getting them in correctly and ruined a few. It is easiest with 2 people, have one person in charge of the shaft and one concentrating on keeping the shims in line with a couple of picks. Then slowly push the shaft into its place.


    Now I have a question for you....

    Do you remember how far the shaft goes into the case? I used a hammer to pound it in but it didnt seem right. SO I pressed it in and now when I engage 4wd the front output seems to have a heavy load on it, whereas before it seemed to turn effortlessly. I wonder if I pushed the shaft too far in.
     
  4. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    I am almost positive, that is NOT the way it goes. It could be the reason you are feeling a "bind" too. You have the idler gear with two races pressed into it in opposing directions. You place one bearing into the race on one end of the idler gear and place that end down on a flat surface, you then put the spacer/collar in down the center and it sits against the face of the installed bearing, you then put the shims on that (using grease on the spacer and shims to keep them together) and then install the other bearing. The spacer and shims dictate how close the bearings (which are in opposing directions) can be (distance between the two). More shims equals increased distance, less obviously equals less distance. The case itself (even though cast) will give and try to pull the bearings in toward the races as you crank on the nut on the idler shaft. The shims and spacer keep the bearings from moving toward each other (and puts pressure on the case and nut as you tighten it). Too many shims and you will have a very sloppy idler gear (moves excessively front to back), and not enough and you will have a bind on the idler shaft (won't move front to back), and just enough and the idler gear should move .001 to .002 inches (per a dial indicator).

    If you are used to shimming different things it may be different for you (lefty tighty instead of righty tighty so to speak).
    It's a little different principle than say the carrier bearings in a differential. Too many shims will make the carrier bearings too tight, and not enough will make it too loose as the shims are to the outside of the bearings and these are to the inside of the bearings.

    You can think of the idler shaft shims in the t-case more like the crush sleeve on the pinion bearings. The crush sleeve crushes to allow the distance between the two opposed pinion bearings to become smaller (take up the tolerance), not crushed enough (similar to too many shims on the t-case idler shaft) and you have excessive play, and if crushed too much (similar to not enough shims on the t-case idler shaft) you get a bind and worn out bearings due to too much pressure.

    Let me know if this makes sense. I know what I mean, but I'm generally not to good at getting it across in words (just ask my G/F /forums/images/icons/blush.gif )

    Also note it should not matter which side of the spacer the shims go on as they are only increasing the distance between the two bearings.

    Please correct me if you KNOW otherwise.

    P.S. It looks like I'm going to have to update my 205 rebuild article to include a little more detail (my bad to begin with).
     
    KevinsK5 likes this.
  5. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

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    Chris,

    You are 100% correct! The shims adjust the end-play of the idler gear. They go in between the bearings along with the solid spacer. I was thinking .002-.004 was the correct setting though.

    Mike
     
  6. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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  7. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    No problem, you were trying to help.

    That illustration looks a little weird though. Although the locations and "types of parts" is correct, look at the shim size compared to the spacer and the types of bearings they show for the idler assy. (they show flat caged vs tapered rollers, which should not work in that installation). I thought drivetrain.com new their stuff. Either that or it's the ellusive aluminum version 205 /forums/images/icons/tongue.gif /forums/images/icons/grin.gif
     
  8. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    1 more question....(sorry to take over the post here..)
    Should the front output yoke have a load on it or should it turn with ease with all new bearings. When I say hard to turn I mean it takes like 10-20 ft lbs to turn it so its not like real bad, but its tighter than the rear output.

    1 more thing...per chiltons when rebuilding the 205 they say the lash can be .000 to somthing like .004 I cant say for sure on the .004 but there is no doubt I remember the .000. So I think I set mine at .000. Will it end up burning the bearings?
     
  9. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    1 more question....(sorry to take over the post here..)
    Should the front output yoke have a load on it or should it turn with ease with all new bearings. When I say hard to turn I mean it takes like 10-20 ft lbs to turn it so its not like real bad, but its tighter than the rear output.

    [/ QUOTE ]

    It should be harder to turn (but should not be that much harder and barely noticeable by hand). The way the 205 is setup the all gears turn together (even when t-case is in Neutral). All that shifting does is couples the rear output and or front ouput to the Hi/Low idler gears depending on which range is selected.

    When in Two wheel drive and you turn the rear output, you are turning the rear output, front output, idler shaft, and front output gears (but the front shaft may or may not spin as the gears are not couple directly to the shaft in 2wd, but may slightly due to parasitic drag). When you shift into 4wd you are only adding the front shaft to the equation. If it is only tighter in 4wd I would say something is amiss with the front output shaft (unless the idler shims are messed up) and the extra input/output from the front shaft being coupled to the idler gear causes the idler assembly to want to push against the case (due to something like 0 lash). This is MY best guess without actually seeing/working on it. I would say something is definitely not right though.

    </font><blockquote><font class="small">In reply to:</font><hr />
    1 more thing...per chiltons when rebuilding the 205 they say the lash can be .000 to somthing like .004 I cant say for sure on the .004 but there is no doubt I remember the .000. So I think I set mine at .000. Will it end up burning the bearings?

    [/ QUOTE ]

    I have never heard of the .000 tolerance, and not to say that is incorrect, but I thought all tapered bearings needed some backlash so they are not overly preloaded and allow room for lubrication. As for burning up the bearings, my best educated answer (remember I am no mechanical engineer) I would say 0 tolerance is not good for the bearings and probably will cause premature failure. I would definitely suggest a minimum of .001 for proper preload and lubrication.

    Remember, I have had a good deal of experience with these but am no Expert authority on bearings and proper tolerances. I will say though that 0 tolerance on tapered bearings scares me!
     
  10. m j

    m j 1/2 ton status

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    I think zero is too hard to set so they use .001 to avoid preloading.
    thanks Leadfoot
     
  11. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Never thought about that, but it does make sense, as anything less than zero (too tight) is 0 (as far as preload distance tolerance), so finding the initial zero would be tough for the average do-it-yourselfer.
    Thanks mj
     
  12. KK5 Native

    KK5 Native Registered Member

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    I see that this is an old post but very helpful to me. I have disasembled (3) transfercases and all of them were different. The exploded views in the manuals are absolutely confusing. I've found out that a lot of people that offer information don't completely know what they're talking about.

    I just got my case back from the machinist to accommodate the large bearing on the 32 spline input shaft needed for the ORD doubler and am going reassemble it here soon. I'm hoping that the shims I have will suffice. Measuring the end play of the idler shaft from front to back seems to be pretty crucial to the set up.

    Just to clarify, after assembly of the idler gear, bearings, spacer, shims and torque the shaft bolt to 138 ft. lbs. I will place the dial indicator at the back of one of the gears. Then slide the idler gear front to back to take the measurement?

    The last case I disassembled had a lot of slop/end play form front to back and I was wondering if that had anything to do with it popping out of 4HI? There is no way it was anywhere close to the tolerance.
     
  13. sweetk30

    sweetk30 professional hooker Premium Member

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