vibration at 30km (18mph) to 40km (25mph)

[vroomzoomboom]

oh so here is what i think was happening. the old leafs were sagged, and the front bushing were so worn out that it was letting the diff rotate downward on acceleration. when i wasnt on the gas, the drive shaft was compensating for the upward angle. thats why this problem with the diff angle was not known until i put the better leaf packs in.

 

[gmanpaint]

That's just awesome to hear!

 

[Dono]

Awesome fix!
I'll be asking to borrow your angle checker at some point this summer.

All the way to 100mph and no vibration. :notworthy

 

[vroomzoomboom]

whats mine is yours don. and yup 100mph no vibration.....with no front drive shaft i should add...

 

[delexploder]

Awesome! Im very glad you guys figured it out, not sure if I'll have this problem with mine but at least if i do I know what the problem is, gman, awesome video!

 

[4pointslow]

Fixed

Good Job!!!!!
Glad to hear Evil is well now!
Did you happen to take measurements afterwards to see where they are?
The picture of the shim is from the rear right? So the shim pointed the front of the differential down?
What was involved in the shim selection process?

 

[Dono]

Id like to check my front and rear pinion angles. I have a feeling that even if just the transfer case is changed, the weight of the larger 4406 changes the angles on both front and rear.
This also makes me wonder if the heavy duty (poly) trans mount from a Mustang that Tim modified to fit his truck would bring the transfer case angles back in line.

This is a huge ah-ha moment for me, as I really had no idea how critical these angles are.
So, delexploder, I'd be really interested in the pinion angles on a stock transfer case. Maybe before you pull yours out, take measurements. In theory (Please correct me if I'm wrong) the trans mount height could be adjusted to make the pinion angles (Front and back) the same as they were out of the factory).
My thinking is.....If you raise one side of the transfer case, the other side lowers (Along with the transmission). By doing this we could match the factory pinion angles.

Thoughts?

 

[gmanpaint]

To see how the diff articulates on acceleration, check this out.




I also started to think about the rear axle perches and where they are placed on the 8.8 from the factory. I would imagine they differ from 2 door to 4 door because of the distance from output to axle is different. This is just a thought, and I might be wrong, but researching a spring shops, or axle shops spec books would reveal the answer.

If they are different angles, this is something to think about when we are swapping axles out, or using the bigger 4406 T-case. :scratch:

 

[delexploder]

I think it would be easyer to shim the front diff, solid Polly bushings, drill the hole with a little angle to it then a sleeve to keep it from distorting, if you want to play with the tcase I would say remove the locator pin, elongate the holes in the tranny tail adapter with a bur bit and you should be able to index it, but that may put the front driveshaft into the cross member, but as far as up or down with the case, I personally dont wanna deal with what that will do to the motor end, like the exhaust and the fan and everything else, my sport is at factory ride height and im sure being lowered made Tim's angle on the rear put it further out of plane than mine but with the extra length of the 4406 im sure I'll have an issue, I'll grab an angle finder next time im at the shop and check the front on it as well as my mounty and see how off they are

 

[delexploder]

Another awesome video, believe it or not when i first got my sport the pinion would climb so hard my driveshaft would get rub marks and when I got duels it would smash the driver side tailpipe into the underside of the truck, that's why I laugh at the guys who swear by the fit shock, its IMO not there so much for stability as its more like a pinion snubber, oh im also looking at the pile of crown Vic rears at the shop, they have a factory whatts link and pinion snubber ,

 

[Dono]

I think it would be easyer to shim the front diff, solid Polly bushings, drill the hole with a little angle to it then a sleeve to keep it from distorting, if you want to play with the tcase I would say remove the locator pin, elongate the holes in the tranny tail adapter with a bur bit and you should be able to index it, but that may put the front driveshaft into the cross member, but as far as up or down with the case, I personally dont wanna deal with what that will do to the motor end, like the exhaust and the fan and everything else, my sport is at factory ride height and im sure being lowered made Tim's angle on the rear put it further out of plane than mine but with the extra length of the 4406 im sure I'll have an issue, I'll grab an angle finder next time im at the shop and check the front on it as well as my mounty and see how off they are

The point I was attempting to make is that by making the output angle the same as factory on one side of the transfer case, the output angle should become the same on the other side (By adjusting trans mount height only). This would, in theory, bring the motor, trans, and transfer case right back in to factory specs.
I would never suggest attempting to just adjust transfer case angle.

I would guess that the trans mount might need to go up 1/4 inch or so. That wouldn't affect the motor, but greatly affects pinion angle's and vibration.

 

[delexploder]

I agree with you and Tim as far as the mount is being smashed by the weight and throwing the angle off, but I also think if we could rotate the case downward it would bring the front output closer to the angle of the 4404, remember the width of the 4406 also kicks the front shaft outward and its index is also a tad higher so that can piviot the output out even more than just the inch wider of the 4406, but reclocking the case to fix that missalignment may get into the cross member,that's why I said maybe shim the front diff

 

[Dono]

Ah, I understand now. I was under thinking it.
I'll have to climb underneath and see how to deal with that front diff. If I remember, that one top pumpkin mount might not be easy to shim in one direction or the other.

 

[delexploder]

Yea I know its making my head hurt, sooo glad I have the manual hubs, the front shaft vibration is not so much an issue for me, there was a thread a while back where someone figured out the front output clocking issue I just cant remember who,

 

[vroomzoomboom]

Good Job!!!!!
Glad to hear Evil is well now!
Did you happen to take measurements afterwards to see where they are?
The picture of the shim is from the rear right? So the shim pointed the front of the differential down?
What was involved in the shim selection process?

no, i didnt take any measurements afterwards. yes, right rear. and yup, you have to put the shim fat side facing the rear of the truck if you want the diff to point down. well, that is on our trucks because the rear diff sits above the leafs

I also started to think about the rear axle perches and where they are placed on the 8.8 from the factory. I would imagine they differ from 2 door to 4 door because of the distance from output to axle is different. This is just a thought, and I might be wrong, but researching a spring shops, or axle shops spec books would reveal the answer.

If they are different angles, this is something to think about when we are swapping axles out, or using the bigger 4406 T-case. :scratch:

i dont think they are. in earlier 95, 96 sports they used a dc shaft and i think that was the only difference up till 01 when sports had a full leaf pack under them.

don, dex, i cant say for sure if i nailed it making the cross member when i put the polly mount on. i know i am thinking of remaking another one just to see if i can bring the font angle down and go from there.