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Back on the road again (with a problem)

EIB8400

EIB8400

1/2 ton status
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Jan 11, 2009
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Location
Delaware, Ohio
I finally got my truck back on the road after a couple of months :D. I did an axle swap, 10b/14bff, rear disc, new rotors, calipers, pads all the way around, DIY4X shackle flip, 4" front springs, ORD extended stainless lines. This was fun in my gravel drive way with hand tools..

I pulled it out onto the street, and everything was fine upto 15mph when I started getting a BAD driveline vibe. The vibe goes away when I let off the gas. Drove it about a block to a friends house so he could help me find the problem. Everything was running fine before the axle swap so I thought that it was something wrong with the new rear axle. We put it up on jack stands, started it and put it in gear. It seemed to be coming from the rear end but, upon further investigation, it is coming from my transfer case. Sounds like the chain is skipping teeth and when you let off of the gas and coast it sounds like the teeth on the gears aren't meshing correctly and grinding a little bit. :mad:

The transfer case was about a quart low so I topped it off and of course it didn't help.

Everything was fine when I parked it. I had it in 4x4 hi the whole time it was parked. So, what could be wrong with it?:dunno:

85 K5, 305/700r4/np208
 
Did you reuse your old driveshaft and use a conversion u-joint, or did you get another shaft?

Sometimes just the slightly greater driveshaft angle that you get from a 4" lift will amplify driveshaft vibration issues that you already had but didn't notice before the lift. What I'm saying is, I doubt it's the transfer case because you haven't messed with it. When I have any kind of problems, I automatically suspect the things I've fixed/modified as the culprit. I go from the most recent work I've done and go back from there. In this case (no pun intended), you've had the driveshaft loose recently, so I would suspect that first if it were me.
 
Yep, I would suspect the shaft as well. How old are your u-joints? You can lower the tranny cross-member around an inch to help the angle, although that usually isn't necessary with only a 4".

What kind of driveline angle do you have now?
 
Same drive shaft with a new conversion ujoint. The spring perches were moved and rewelded. If it was just the drive shaft, would it make the transfer case make bad noises?
 
Your angle is probably good. I still think the shaft is vibrating and causing the case to act up and sound bad. I would suspect the new u-joint and the way it's installed (you'd be surprised how much your shaft can vibrate if you don't center the u-joint up and do the caps just right), the pinion yoke on the new axle (maybe the bearings or some related stuff is messed up) or the shaft itself. It may have gotten dented or had the weights knocked off it while you had it loose doing the axle swap. Just throwing out some ideas. Are you sure the new perches are welding on just right? Is the truck tracking straight, or were you able to drive it far enough to be able to tell?
 
A pic of the drive shaft angle would be good. Without a CV shaft the joint angles should match each other. With a CV shaft the pinion should be pointed at the tcase.

Did you happend to drop the new joint or drop a cap off? If so one of the rollers may have fallen out.
 
The weights are still on the shaft. The shaft wasn't thrown around or anything. It stayed in the truck the whole time until I had a friend put the new joint in at his shop. If it was the pinion yoke or the bearing on the axle were messed up would I be able to see it while the truck is jacked up and the shaft is spinging? Every thing seemed to be rotating great except the transfer case noise and vibes. Should I pull the Ujoint caps and drop the shaft and then reinstall it? The yoke has little nipples on the edges so that the ujoint is centered on the yoke.

The perches should be on correctly. I had a friend come over that is a welder and he helped me get everything lined up and welded it for me but, I have not driven it far enough or had someone tell me if it is tracking right.
 
Hmmm...this is a hard one. How much of the slip shaft can you see when the truck is on level ground? Maybe there isn't enough spline engagement. Seems like it wouldn't have caused a problem that quick though. It may be time to take the transfer case out and tear it down. Isn't there and inspection cover you can take off to check the chain while the case is still in the truck? I would do that first to see if the chain is stretched out. I can't remember if you said the Blazer was shaking when you drove it in 2wd. I know you said the case was in 4Hi while you were working on it.
 
Oh yeah. What about the gears in the new 14 bolt. How are they? Maybe they aren't set up right. You're experiencing the vibes only when on the gas. Maybe the ring and pinion aren't set up right.
 
I stuck my finger in the hole :D. The chain feels pretty tight. The truck shakes pretty bad in 2wd. Even tried in 4lo. still did it. The ring and pinion looked very very good and everything seemed nice and tight. I get the vibes on acc. anything over 15mph and bad noises on deccel. Below 15mph it is very smooth.:dunno:
 
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Okay. I still think that's pointing to the shaft for some reason and not the transfer case. Maybe one of the experts will see your thread tonight and post up a solution. Good luck!
 
Thanks for the help. You are prob right. What if I pull the rear shaft and drive on the front? That should tell me if it is the transfer case problem correct?
 
EIB8400 said:
Thanks for the help. You are prob right. What if I pull the rear shaft and drive on the front? That should tell me if it is the transfer case problem correct?
Click to expand...

This was going to be my suggestion if nothing else it will eliminate a potential cause of the problem.
 
I think I'm going to try pulling the rear shaft after work tonight and check it out. What are the chances of the yoke on the axle being bent? Could that make the transfer case make bad noises?
 
EIB8400 said:
I think I'm going to try pulling the rear shaft after work tonight and check it out. What are the chances of the yoke on the axle being bent? Could that make the transfer case make bad noises?
Click to expand...

Maybe so. Or the pinion bearings, although they would probably letting your ears know if they were going bad. Taking off the rear shaft and driving with the front shaft wouldn't neccessarily tell you if something was wrong with the rear output on the transfer case. That would just show you if something was wrong with anything from the rear transfer case output back to the rear wheels. Take it off though and if you still get some vibrations, you know it's the case. Good idea.
 
Is there anything in the rearend that could be messed up and cause 98% of the noise and vibes to show up in the transfer case? I pulled the covers off before the swap and the gears all looked good and there wasn't any play/slop anywhere. Could something be messed up in the carrier? Thanks for the help.
 
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