Vibration after dropping transmission

[Shawn]

Getting a severe vibration after replacing the flex plate on my m1008. Now... I don't believe its the new flex plate. I can rev the engine in neutral and keep it at high RPM with no vibration. Soon as I take it for a drive it gets up to 40+mph, I get a bad vibration. If I coast down a hill and put it in neutral while doing 40+mph I still have vibration. To me, the problem is pointing to the driveshaft. Unfortunately, I did not mark the driveshaft when I pulled it and I don't believe its important when we are talking a one piece balanced shaft with a slip yoke. I will take it back off and rotate it 180 degrees and see if that helps. I'll also inspect the u-joint itself. Maybe something with the caps or bearings. I did put some spacers between the new flex plate and torque converter to achieve 1/8" of gap. It was 1/4" before and I read it needs to be 1/8 - 3/16 of gap. I can also take out the spacers just to see if it helps.

With all that being said, can it be anything else that's causing excessive vibration?

 

[mrk5]

I had to use spacers like that with the 700r4 I ran in my K5 and the crew cab. They were just washers and never seemed to cause a problem.

Only thought I have is trying to remove the rear shaft completely, but I know driving on front shaft only isn't usually very smooth anyway so you probably couldn't tell anything.

Any chance the engine or trans mounts might be messed up?

 

[skunked]

I had a similar symptom with my IFS truck when I failed to seat the u joint correctly in the front axle yoke. One of those dummy moments but it was an easy fix.

 

[Shawn]

I had to use spacers like that with the 700r4 I ran in my K5 and the crew cab. They were just washers and never seemed to cause a problem.

Only thought I have is trying to remove the rear shaft completely, but I know driving on front shaft only isn't usually very smooth anyway so you probably couldn't tell anything.

Any chance the engine or trans mounts might be messed up?

Ok, good to hear. They were just normal washers too and I made sure to measure a stack of 2 with a caliper to make sure they were all the same thickness. Good idea on removing the rear shaft. I will need to clamp a small pop bottle over the Np208 slip yoke snout so it doesn't leak out. I don't think its the trans mounts since I never touched or unbolted those. I'm sure it was not spaced down either at the crossmember to frame.

I had a similar symptom with my IFS truck when I failed to seat the u joint correctly in the front axle yoke. One of those dummy moments but it was an easy fix.

Thats one thing I'm hoping it is. I couldn't tell if it the ujoint cups were all the way in the yoke but the straps seemed to be bolted all the way down. I will re-do that and see if I fudged something up.

It just SUCKS to fix one thing and creates a whole new problem.

 

[ktmoutfront]

On a 1 piece drive shaft with a slip yoke into he transfer case, there is not an indexing to the rear axle or transfer case.

I saw one that a guy accidentally knocked the weight off of the drive shaft. Vibrated above a speed under load or coasting.

 

[Shawn]

Well... I feel like a idiot now....

 

[ktmoutfront]

That will cause it also. Easy fix.

 

[Wes Harden]

Yup easy fix, glad you are thorough enough to go back and find the issue. Most guys here would. some peps out there would just run it.

 

[skunked]

Well... I feel like a idiot now....

View attachment 376379

where’s my cookie!?

glad to see it’s an easy fix.

 

[Capt Ron]

If the other side looks correct you might have a needle sideways in the cup.

 

[mrk5]

Haha! Nice!

 

[Shawn]

If the other side looks correct you might have a needle sideways in the cup.

It's good. Other side had a small gap so I just had to force it up to get that side in the tab. All fixed and smooth as @CK5 's shaved head!