drive line help on lowered 68 lwb

[tallic68]

First off. Thank you to everyone for your help and all the discussions on this page. When I have issues one of the first places I turn is here. Almost all of my problems have been solved with a search and through showering of results and l find someone with the same problem or at least a close problem and the solution to the problem.


I haven't really found a close enough problem and solution so I'm doing a thread to get some help and for it to be found by the next guy that does have this or close to this problem and help them.

Little history. 68 long bed 5.3 4l60e 12 blot rear. Conversion done in 2012 ish. lowered 2 front with springs and 4 rear springs and blocks. Daily driver for almost 15 years. No issues aside from carrier bearing went out 3 time in the time frame. Due to my commute since 2020 she has been a garage queen and I have started putting good money into her making her more "Showie"

In comes the issue. Keeping in mind the carrier bearing. I did a QA1 suspension swap. I don't know the exact amount of drop from stock. But the upper most curve of the wheel wells are now in the 28" area. Im guessing she is lowered 4-5 front and 6 or so rear. Have not perfectly equalized the four corners yet as waiting to drive a bit and for it to settle in before I get exact.

I am fighting a massive drive line vibration. 55-60 mph with two piece shaft and 50-55 mph with one piece shaft along with a quick wobble of column shifter off the line. I have replaced the carrier bearing with a cpp poly polished bearing. Added a cpp slip shaft to the rear. Confirmed balance of the two piece shaft. Had a one piece shaft made. Double confirmed balance on one piece shaft. The QA1 system has an adjustable pinion system. I have tried to match pinion to the trans angle. Tried to match pinion angle to the angle of the first shaft. I have it set up now to match pinion angle to engine angle with a one piece shaft. I've come the the conclusion that the engine angle is to much.

2002 5.3 4L60E early version dirty Dino slider mounts. 73-85 bbc perches and rubber clamshell mounts. Dirty dingo adjustable trans cross member (fully adjusted up) to the highest is can be. I could flip the rubber mount platform and get quite a bit more higher but I will be hitting the trans tunnel.

[tallic68]

She is on jack stands right now. Rear stands are on the axle as to keep her at ride hight and suspension loaded. Frame is level. Engine angle is at 6.5 deg taken off the crank pulley. Trans can not be pushed up due to trans tunnel. I do not want to put a high hump in.

I have plenty of room up front. AS of right now I have a speed engineering low profile pan on order from az pr perf. holly perches and f body rubber clamshell mounts.

[tallic68]

Once I get the pan in I will see where she sits. Then see how the hooker holly perches and f body mounts work. If they don't help out I guess ill be fabing some mounts.


Second issue will be where the A/C and power steering pump will sit with the engine lowered. As I really don't want to swap pumps out or change up the hole front serpentine system if at all possible.

[tallic68]

Does anyone have suggestions, Experience or anything else.


Again. Thank you all you this site and all of your knowlage.

[tallic68]

Here is the shaft angle and trans adjustments

[HO455]

I'm not sure I would take the engine angle measurements off of the outside ring of the harmonic balancer. The rubber elastomer may not be holding that ring true to the crankshaft. (I couldn't tell you how many hundreds of wobbly balancers I've seen over the years.) I've always taken the engine angle measurement off of the transmission yoke.

Taking the angle measurement at the yoke means you can also turn the yoke and get readings 180 degrees from each other thus assuring yourself that the yoke is true.

And on the subject of your yoke how much spline engagement do you have?

It looks to me that unless you have an extra long yoke you may be short on engagement which may be your problem. I would check the runout of the yoke with a micrometer with a magnetic base. Once set up turn the yoke 90 degrees and record the readings. Take a second round of measurements but this time give the yoke a medium tap with a dead blow hammer and then record the reading. There should be very little play or differences in the readings. (I don't remember the spec off the top of my head. But I'm pretty sure the interweb has the answer.)

I just posted some links and information in this thread, they may help you.

http://67-72chevytrucks.com/vboard/s...d.php?t=846652

All this is my opinion and that along with a $10 bill will buy you a steaming hot cup of Joe just about anywhere.

Good luck and keep us updated.

[tallic68]

Here is total yoke length and what’s left once in place.

I understand what you’re sayin. But. Still has 6.4 def working angle

[Sheepdip]

HO455 is correct on your yoke, it looks short of where it should be. Most driveline shops have you set the yoke all the way in until it bottoms out on the transmission output shaft, then measure center to center of the u-joints. They then they do the math of shortening it (usually 1") or as required.

There are other methods to measure the driveline length required, and other parameters that come into play such as lowering, 1pc., 2pc. etc.

Your local driveline shop is the one to ask.

[tallic68]

Here is the two piece shaft installed. The carrier bearing mount in the lower set of holes as to keep the forward shaft closest to the engine angle.

[Richard]

What is the pinion set at with the one piece and drive line set at .1 degrees? Angled up or down? Here is a great article by Tom Woods discussing driveline angles, ujoint life, etec. https://4xshaft.com/blogs/general-te...veshaft-angles It focuses on a 4x4 but the information applies to all custom vehicles altered from stock. Another on vibrations https://4xshaft.com/blogs/general-te...aft-vibrations
Also something on spline engagement for those that commented. Think you are fine with 3" of spline engagement. https://4xshaft.com/blogs/faq/how-mu...uld-be-showing

My last two 4x4's have had more than 6 degrees of working angle, were daily drivers and ujoints or vibrations were never a problem. My current build has over 10 degrees working angle at tcase in rear, front has even more. I decided to use a double cardan CV on the rear as well as front. Even with the CV in rear shaft those two ujoints will be at over 5 degrees full time. Do not expect any problems.

[LNP]

Check the angles on the yoke of the trans and the rearend not on the driveshaft. Your setting the rearend angle in reference to the transmission not driveshaft to transmission. Turn the yoke till a ujoint cup is at the bottom then measure angle. Make sure your angle gauge sits flat and not angled.

[tdangle]

My thought is a 6 degree operating angle at the front u-joint is way too much. You need to somehow get the engine/trans combo to about 3 degrees. Then you can match the rear pinion angle. Spicer has an app that will calculate operating angles. Good luck

[LNP]

I agree with that 6 is too much. Engine needs to be 3 degrees downward and the pinion 3 degrees upward

[Jason Banks]

Hopefully getting the engine lower with the Holley mounts will allow you to get a shallower angle for the engine.

Page 4 Post 91 of this thread I posted some pictures of where the engine and AC compressor sites with the Hooker/Holley Mounts - https://67-72chevytrucks.com/vboard/...=790866&page=4

[OregonNed]

Tremec has a pretty good app as well for calculating..

[tallic68]

Jason. Awesome thanks. I will read your full thread. You have no idea how many times I’ve searched and never saw your thread. Thank you very much.


**edit**. I did see that thread and your post. The pic of the drivers side mount was my deciding factor to get the mounts. Seeing that the ears were further down the perch and closer to crossmember than my 73-85 perches I have.


I’ve been using the TREMEC and spicer apps and as you can guess no matter what I did they told me the angles were bad.


When the engine was at 6.5 deg. The pinion was matching at 6.5 deg up shaft was 0.1. Meaning a 6.4 deg front joint angle and a 6.6 deg rear angle. =vibration.

I have the mounts out right now and truck pan sitting on cross member with a 1/2 piece of plywood in between. Engine is at 5.4.


I’m probably going with the two piece due to the yoke only having 2.5 inches of engagement when installed. Don’t want to rebuild the one piece as it was built before I did the QA1 and centered the rear end moving it back 2 or more inches.

[tallic68]

Am I correct that the first shaft is to be close to the engine angle but not perfect .5-1 degree difference to allow lubrication. Then the pinion angle is to match the first shaft with no more than 3 deg working angle on both the second and third joint.

Example

Engine is 4.5 deg down
First shaft 4 deg down
First joint working angle .5

Second shaft 2 deg down
Second joint working angle 2 deg

Pinion angle 4 deg up matching first shaft
Third joint 2 deg working angle.

[LNP]

I myself have never checked driveshaft angle I have always went by the engine/transmission angle and the pinion angle. What lubrication are you referring too?

[tallic68]

U joint lubrication. All the research I have done say u joints can’t be at a 0 working angle as the will not move any and unable to move grease around to lubricate the needle bearings.

[LNP]

Originally Posted by tallic68

U joint lubrication. All the research I have done say u joints can’t be at a 0 working angle as the will not move any and unable to move grease around to lubricate the needle bearings.

After 30 plus years in the automotive repair field thats one I have never heard before. I dont argue it at all just never heard of it. I figure the high rpm a driveshaft turns added with the movement in the joint each time the vehicle moves will insure grease movement. There will always be an angle on the driveshaft as the pinion sits lower than the transmission output shaft as long as everything is installed correctly.

Is that a aftermarket multi-port injection set up you have? It looks sharp.

[tdangle]

Originally Posted by tallic68

Am I correct that the first shaft is to be close to the engine angle but not perfect .5-1 degree difference to allow lubrication. Then the pinion angle is to match the first shaft with no more than 3 deg working angle on both the second and third joint.

Example

Engine is 4.5 deg down
First shaft 4 deg down
First joint working angle .5

Second shaft 2 deg down
Second joint working angle 2 deg

Pinion angle 4 deg up matching first shaft
Third joint 2 deg working angle.

This is my understanding when working with a 2 piece driveshaft. I spent 2 years trying to fix a vibration with my stock C20. Reworked everything multiple times and all it did was move the vibration around in speed. In my case it was the slip joint between the 2 drive shafts had some play that the first driveline company did'nt after 2 balances.

[tallic68]

So after weeks of swapping parts, measuring angles, rebalancing shafts, cutting holes and so on. I believe I have finally solved the problem.

Quick recap. After installing QA1 front and rear suspension kit. I had a crazy vibration at 55mph. Pinion angle changes did nothing. One piece shaft did nothing, actually making it worse. Angle measurements showed a beginning engine angle of 6.7 deg. I started with lowering the front of the engine. Hooker black heart c10 perches with f body mounts. Speed engineering low profile oil pan.

[tallic68]

These changes brought the engine angle down to 4.7deg. Still had vibration. The only way to get the engine close to 3 deg was to raise the tail shaft of trans. With about half inch of clearance between the output shaft housing and the floor and less clearance to the pinch weld of the floor and firewall meant switching to high hump which solved both clearance issues with room to spare. I Cut the hole in the floor, flipped the adjustable perch on the dirty dingo trans cross member and maxed it out. Now the engine angle is 3.1.

[tallic68]

Now the drive shaft had a “v” shape to it due to the carrier bearing. I Flipped the carrier bearing mount and placed it so the front shaft had .5 deg down angle. Adjusted pinion to match the angle of the front shaft per a tech article on the QA1 site. This is one of the major questions I had about two piece shafts. Does pinion match engine angle or does it match the fixed shaft angle. I could not find that answer anywhere except the QA1 article linked. And this was the only place I found this info. https://www.qa1.net/tech-center/tech...ngle-explained

Another good two piece shaft article
https://www.motortrend.com/how-to/06...iveshaft-tech/

This is a good video that helped explain the problem to my wife to explain why my truck has been on stands for so long and what I need to do to fix it.

https://www.youtube.com/watch?v=YgNZfIR-8Ng

I’ll throw this one in in case no one has seen it.

https://www.youtube.com/watch?v=Idk3BVDVHq4

Once all this was done.
Engine angle started at 6.7. Now it’s 3.1 degrees.
Fixed shaft 3.5 degrees.
First U joint working angle .4 degrees.
Rear shaft .9 degrees.
Second U joint working angle 2.6 degrees.
Pinion 3.6 degrees matching fixed shaft.
Third U joint working angle 2.7 degrees.

No vibrations. On a test I had the truck to 90 on the road and smooth sailing

[tallic68]

Yup