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I have to hold myself back

E

Espen88k5

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when I take off from a light or full stop
frown.gif

I have a problem I would like your advive on. My 4"+3"lifted 88 K5 on 35" Mud/T shudders on take off. I have changed both U-joints in the rear driveshaft, inspected the ring and pinion in the rear diffrential(no shavings or wear).
I have come to the conclusion that something is making my driveline twist to much on accelaration and it's causing the u-joints to bind when it's at most stress. I have no vibrations at any speeds as soon as the truck gets rolling. When I did my T-case rear seal I noticed that the rod that connects the t-case to the engine had broken off a long time ago(by the rust where it had broken off) I welded that back upp and felt a litle diffrence but not much.

Now to my question, I remembered a post about buying and replacing the oil soaked trannymount and feeling almost like he was given a totaly diffrent truck back. Mine also has had oil from the t-case slung around by the slipyoke and the entire undercarrige is soaked with oil and I know the tranny was serviced 3-4 years ago, and they didn't change the mount I'm sure..Also the suporting rod that has been broken for a long time, not doing the suporting it's suposed to cant have helped the rubbermount out much.

Any thought's or advice on this?

I want to be able to give it at least half trotle when leaving a light, not baby it into motion first before aplying some force.
I have 3.08 gears by the way so the forces working between the engine and the 35 Mud/t getting it rolling are lots more than what it was designed for.


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Definitely change the tranny mount - after I got rid of my old one, I could hardly recognize the thing. I even got completely rid of my 75 mph driveshaft vibration. One piece of advice is that if you go urethane, change over to urethane motor mounts too - otherwise you'll have a whole new annoying feeling in the truck (I have done this)

Special thanks to those lost from IAFF Locals 94 and 854 - You shall never be forgotten
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Sounds like that's my problem. Started after I went to 35's.
Is it a fairly simple job to change the motor and tranny mounts? Anyone have a description of the work involved? How expensive are they and who offers them?


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I am thinking more towards axle wrap. Is the lift in back blocks? If so that may be the problem.
How do you prevent it? stiffer springs, the flip. Do a search for more answers

Rob 85K5

<font color=orange>Bleedin' Chevy Orange</font color=orange>
 
Tranny mount is really easy, can't remember the cost tho. Engine mounts aren't too bad but can be tricky too. Do them one at a time, meaning, don't lift the engine and pull them both at the same time. It's much easier leaving one intact while you do the other. I think these mounts run about 15. each.

1984 K-5
4" lift
35x12.5 MTs
buildin a 400 for it, any info greatly appreciated
 
I did both of mine at the same time. Did it on both trucks infact. Course the one truck I was dropping a engine in at the time and while I had the hoist I rolled the other truck up and flited the engine. Was a peice of cake that way
smile.gif

My bet is motor and tranny mounts for the problem. If that doesn't cure it you may want to pull the drive shaft and inspect the splines and see if it has any unusual wear. Also if the truck has had a recent lift and you messed with the u-bolts on the axle retorq them.

I don't need no damn shop manual, I got a pornographic memory.
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75 Jimmy, Dollar
Grim-Reaper
 
The tranny mount is a no brainer.
The Engine mounts are basic remove and replace but are a lot harder to get to, at least on my 90. I also had problems with the parts clerck being able to locate the correct mount, as chevy has 50 different motor mounts.
I dont really think your motor mounts would cause this. They usually cause more of a clunk at take off.
One more thing to look at is possible having your driveshaft balanced.
One more cheap thing to do is take the rear shaft out and put some grease inside the slip yoke and re-install the driveshaft and see if that doesn't help. Sometimes worn splines in the slip yoke and on the T-case output shaft can cause a bizarre list of little gremlins that can bug the piss out of the best of patient men. Good luck.

"you know... the guy with the BAD A$$ spring perches!!!
laugh.gif

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I have dealt with this same problem before. I changed the tranny mount, which was definately needed. I ripped out the blocks and did the shackle flip. I replaced both U-joints. I made sure the pinion nut was tight and that the U-bolts were tight. Most of this stuff helped a little, but none of them were the source of the problem. I believe that It is caused by the stupid slip-yoke design of the NP208 transfer case. The yoke doesn't always fit very tightly on the output shaft and this allows everything to move around as the driveshaft moves at low speed. As you speed up, the inertia of everything prevents it all from moving around so much. When the truck is lifted, this makes the joint looser by shortening the overlap of the splines.

If the problem was axle wrap, it would be worse as you gave it more gas and at very light throttle, would not be a problem at all. But you, like me, already know that it is not really proportional to torque. If it was nothing but bad U-joint angles, it would be very unlikely not to have noticeable vibration problems at some higher speed.

The solution should come in 1 of two forms:
-lengthen the driveshaft. That will put more spline length in contact and at least make the slip-yoke work as well as it is supposed to.
-Eliminate the slip yoke in favor of a fixed yoke by using parts from a Dodge or Ford 208. This eliminates the freedom of movement in that slip joint and fixes the problem. It also reduces fluid leakage with the added bonus of being able to run in front wheel drive if something in the rear drivetrain breaks.

That grease in the splines trick might be worth trying out, though. If a little thick grease gets dissolved into the ATF in the transfer case, that shouldn't hurt anything, considering that there is something like 5 quarts in there.

<font color=green>"Lack of Brains Hinders Research" -headline in the Columbus Dispatch</font color=green>
 
I had trouble getting the right motor mounts as well from a parts store. But finally I got it right.

Are you hearing any loud clunks or anything? I know my tranny mount is shot because after I dropped my tcase I hear a loud clunk. Keep in mind I haven't had it on the road since the lift. This is just pulling it out of my garage. But the loud clunk is my TCase moving up then slaming down on the skid plate. So thats my culprit. You having anything similar happen?

89 K5 Silverado
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Great replyes guys, keep em comming.!!

If My wife dont see me doing this, where could I point a camera to cath what is happening? I figure taping upp my camera to somewhere and go for a litle drive to see if I see something bend or vibrate strangely?

Axle wrap makes the u-joints work at a angle causing it to snag and vibrate, right?. The axle pinion moves down when the spring perches wraps?

I can live with this if it's not damaging anything else than my u-joints. Figure on changing those once a year anyways.
Anything else?

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Mudfrog:
Before I changed my U-joint I would ocationally hear clunks speeding upp after cornering and such. But my topp u-joint was bone dry and had lost most of the roller pins..
My truck didnt come with the skid plate package. I'm looking for one though.

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Hmm... Well it's a good thing your tcase aint hopping around then
wink.gif
.

89 K5 Silverado
<a target="_blank" href=http://mudfrog.rockcrawler.com>http://mudfrog.rockcrawler.com</a>
 
The axle pinion will move upward when there is torque through the differential. The axle assembly will try to rotate in the opposite direction it is trying to make the wheels rotate in. The vibration from U-joint angles comes from having the two angles mismatched. Then the orbits of the two ends of the driveshafts aren't matched and it's path is out of balance. You have to get the joint at a huge angle to actually make the jiont itself bind. Most vibs come from the angles being different.

Road vibrations may make the camera hard to see, but you can do some tests before you even drive it. Crawl underneath and see if you can get anything to move around. It is best to do this with the tranny in nuetral and the parking brake set. See if you can move the top of the driveshaft around, showing slop in the tranny mount or in the slip shaft. By really pushing up and down and side to side on things, you should be able to see the problem, including bad U-joints. The things that you can't find this way are axle wrap and mismatched U-joint angles.

<font color=green>"Lack of Brains Hinders Research" -headline in the Columbus Dispatch</font color=green>
 
Thanks
I'v learned alot today. I will attack this the right way thanks to great people willing to share theire hands on experience. And people wonder why I drive around with a CK5 sticker
smile.gif


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check your transmission fluid!mine does it when it gets too low. and when the filter clogged up! easy and cheap fix if thats it.

who knows?

Chrsi


MY DRINKING TEAM HAS A FOUR WHEELING PROBLEM!
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