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post #1 of (permalink) Old 05-31-2009, 10:13 PM Thread Starter
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Vibration diagnosis.... what's your guess?

I was driving my 78 CJ5 this weekend, and tried shifting the transfercase just to see if everything was working correctly. Of course it slid right into 4H very easily and wouldn't come out again.

I ended up having to disconnect the shifter and remove the linkage that keeps the two shift rods hooked together on my Dana300. I manually put the shift rods in place and drove the jeep home....... to be investigated later.

It seems to me that the Jeep had a LOT less vibration on the way home, than it did when I was driving earlier in the day. The only difference was shifting the transfercase from 2H, to 4H, dealing with the "stuck" transfercase while I was trying to use the lever to shift out of 4H.

Is it possible that having the shift rods in a different position would cause a driveline vibration? Or am I just out of my head, and comparing the 4H mode with 2H mode?

Oh.... and finally, does anybody make a small parts kit to repair this linkage on my Dana300? I know everybody is going to scream to twin-stick it. But I'd prefer to keep it stock if possible. ......... probably going to twin stick it eventually..
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post #2 of (permalink) Old 06-01-2009, 11:08 AM
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The vibration is coming from your front driveshaft turning. It is probably either bent or twisted. I twisted 2 and then went to a 2" diameter shaft to keep from twisting a 3rd.

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post #3 of (permalink) Old 06-01-2009, 11:35 AM
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You can confirm Will's diagnosis by careful inspection. Laying a yardstick along the shaft will help determine if the U-koint yokes are slightlyt out of phase. It doesn't take much to cause significant vibration.

I twisted one front shaft but, because of clearance problems, rebuilt it with same-size 4130 tube. No problems so far.

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post #4 of (permalink) Old 06-01-2009, 03:32 PM
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On the D300 shifting, first suspect is the lever. They bend below the pivot point and cause hard shifting. Also make sure itís tight on the pivot bolt. Next check the hole in the shift plate to see if it has excessive wear. Next are the pins that hold the shift plate. Then check the bushings for the lever pivot bolt.

I think you will find the problem to be external and will not need to rebuild anything inside the case.

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post #5 of (permalink) Old 06-01-2009, 08:05 PM Thread Starter
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Thanks for all the replies, but I think I didn't relay the issue quite clearly......

I was comparing driving the Jeep in 2H earlier in the day to driving it in 2H after my little wrestling match with the shifter.

I'm pretty sure my front driveshaft has a good wobble to it. And I really never use 4H.

But it seems to me that disconnecting the shifter, and manually putting it into 2H seems to have made the Jeep a smoother ride. That doesn't really make much sense to me.

So is it possible that having the shifter connected, and possibly NOT having the shift rods in their "proper" location would cause a vibration?

Maybe my jeep was partially in 4wd and I didn't know it? Causing the front driveshaft to spin and adding the vibration?
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post #6 of (permalink) Old 06-02-2009, 05:17 AM
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That's certainly a possibility. Do you have unlocking hubs? If so, you wouldn't otherwise feel the difference between 2H and 4H.

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post #7 of (permalink) Old 09-01-2009, 11:05 PM Thread Starter
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Question

Tonight I finally got around to re-investigating the Dana 300 shifter. I was expecting to just re-install everything, making it all tight and getting on down the road.

However, while wrestling with the shifter linkage I noticed that the front shift rod wouldn't move. I mean, it wouldn't move at all. The rear shift rod moves pretty easily.

I don't recall having any issues moving the shift rails on the day I had the original problem that lead me to disconnect the shifter.

So now what? I've finally got the front shift rod to move in and out but it's not easy.

Seems as though the rear shift rail would move forward and backward, while the front shift rail remained stationary. I'm guessing this is what caused the vibration that I thought I was feeling. ???

Do I have something bent inside my Dana 300? How hard are these things to pull apart and repair? Or should I keep an eye out for a replacement?
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post #8 of (permalink) Old 09-02-2009, 01:08 PM
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I’m no expert on these but, since nobody else stepped forward, I’ll tell you what I learned about them.

Some of what you describe is normal. The shift rods do not move totally independent of one another. Read up on the twin stick modification, not that you may want to do it but what shifts are possible.

You cannot shift the front without shifting the rear. Front wheel drive is not possible without removing the shift rod interlock pills. The rear must already be in high in order to shift the front into high range. For low, both the shift rod for the front and rear, seem to move together. I think it is also locked out from moving one shift rod to low range and the other for high.

I looked into this when I was thinking about doing the twin stick modification and found out it would do me no good without removing the interlock pills.

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Last edited by CJ7Taz; 09-02-2009 at 02:52 PM.
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post #9 of (permalink) Old 09-02-2009, 08:17 PM
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IN....were you turning the DS while trying to move the front pin? As we all know, you sometimes have to move the jeep a bit in order to get the xfer case to shift....

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post #10 of (permalink) Old 09-02-2009, 08:21 PM Thread Starter
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Yep.... I turned the driveshaft, I didn't turn the driveshaft, I faced north, closed one eye, bit my tongue....... all my normal tricks. Nothing seemed to make it better.

I'm off to investigate it again right now. Hopefully, I'll be able to report back with some good news.
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