New, help please!

[Wes P]

Greetings!

Short story:
I need the factory drive shaft angles and driveline angle (to verify the factory U-joint working angles) of a C20. If you have access to a C20, or the data, please help!

Long story:
I installed a GV overdrive behind a TH400 in an 85 C20. It was my intention to use a one-piece shaft. It looked good on paper. I did not measure the factory drive shaft angles. Big mistake. A one-piece 59" driveshaft fits perfectly but is just too long to balance for highway speed with 4:10s. I have been troubleshooting a highway speed vibration for more than a year. It is silky-smooth below 60mph. No problems. Above 60mph, I get a 1st order vibration that I can not drive through, does not go away with OD off, or in N, I can not eliminate by re-balance, changing differential angle (its not characteristic of a U-joint angle vibration but it was worth a try), or hose clamp tuning (an improvement but still unsatisfactory), etc, etc.

I am no longer troubleshooting the 1-piece driveshaft. I'm going back to a 2-piece driveshaft to:

1. Change transmission yoke from involute spline slip yoke to fixed yoke (inherently reduces run-out under low load).
2. Duplicate the original front U-joint working angle.
3. Achieve identical (cancellation) working angles at center and rear U-joint.

I will fabricate a new carrier bearing mount to keep the front shaft at least the recommended minimum 12". I just need to verify the original working angles. If anyone has a C20, or data, and can tell me the original angles of the shafts and driveline, I can move forward without guesswork!

The alternative is to remove the GV and re-install the original tail housing and shaft for measurement. I want to avoid this.

Many Thanks!
Wes

 

[dvdswan]

Welcome to the site. Have to called customer service at GV? They should have all of that already figured out for you.

 

[73c20jim]

Welcome.

I have a center bearing with housing you can have for $10 plus shipping.

 

[1973c10]

Welcome to the site

 

[Doppleganger]

You must be registered for see images attach

 

[Old77]

 

[MrMarty51]

 

[Wes P]

Welcome to the site. Have to called customer service at GV? They should have all of that already figured out for you.

I have called Gear Vendors, yes. They do not have the angles on record or any installation notes for the C20.

They do, however, have a shop nearby their headquarters that does installations and builds drivelines for their local customers. I will call them and ask if they have notes on a C20.

Thanks!

 

[Wes P]

Hello sir, does the black long bed in the photo have a factory transmission and 2-piece drive shaft? If so, even if it is a C10 long and not a C20, knowing the angles would help!

 

[Wes P]

Welcome.

I have a center bearing with housing you can have for $10 plus shipping.

Thank you but I already have a new carrier bearing for the build.

Do you still have the C20 Custom Deluxe listed in your profile?

 

[Dan Miller]

Welcome from Indiana !!

 

[bucket]

Howdy!

The angles used in stock trucks varied. Some trucks rode higher and some trucks rode lower, just depending on the spring package installed. Especially considering the same axle housing was often used in 2wd and 4x4 trucks and many different lengths of trucks too. I believe they all had roughly the same pinion angle designed into the housing based on where the spring perches were welded on.

In short, I believe you are over-thinking it. A 59" prop shaft isn't that terribly long. It could have been that the shop wasn't getting it balanced very well, the tubing was too small of a diameter, or maybe the angles just weren't that happy and it could have been fixed with some degree shims in the rear spring packs. I'll wager that a large diameter aluminum shaft would have worked great.

But that doesn't matter now anyway. If you are going back to the stock shaft setup, it should be smooth sailing for you. Just put it back how it was basically and if you do need to move the carrier crossmember back, it may be helpful to lower the the bearing down some.

 

[Preston]

Welcome to GMSB from Virginia

 

[SirRobyn0]

Ok stupid question, if you have had the driveshaft balanced and rebalanced, and you have said it's not the typical u-joint vibration is there any chance at all that it could be an out of balance tire, or out of round tire? I'm just saying it would be easy to eliminate, and coincidence happens.

 

[Catbox]

Welcome to the forum.
It is currently raining like crazy here.
Otherwise I would volunteer my son to go out and see what we could find under ours.

Our truck has the SM465 in it, I don't know if that matters or not.

Perhaps you will get your answer before it stops raining, perhaps not.
I will check back later.