Steering vibration

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richshoop

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Apr 4, 2017
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On the last trip. I noticed that while driving UP hill, I feel a slight shudder. Driving DOWN hill, no shudder at all.... What am I looking for?

----- Original Message -----

From: "Bob Dunahugh"
To: "gmclist"
Sent: Tuesday, June 20, 2017 7:25:56 PM
Subject: Re: [GMCnet] Towd MPG penalty

I got 10.2 MPG pulling Linda's 5000lbs Chevy Uplander lift van. With 87 Octane ethanol gas. 78 Royale 403 stock exh, carbureted, and a 3:70 FD. GVW of 17,000lbs. Pulling a car hauler with a car on it. I got 9.8 MPG with a GVW of15,000lbs. So the Uplander seems to have better air flow behind the GMC. With the 3:70 FD. My trans temps went down, and MPG's went up about 1.7 MPG's. That was with the burned GMC. Haven't calculated this 78 Royale 403, and the 3:70 FD yet. Bob Dunahugh
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On the last trip. I noticed that while driving UP hill, I feel a slight shudder. Driving DOWN hill, no shudder at all.... What am I looking for?
==============
 
Loose bolts at inner CV joint to final drive flange also can cause this vibration. They are the high strength bolts that should be torqued to 75 ft
lbs, IIRC.

Hal Kading 78 Buskirk Las Cruces NM
 
Thank you for the hint. I'll check them ASAP!

----- Original Message -----

From: "Hal Kading"
To: "gmclist"
Sent: Friday, July 14, 2017 8:59:31 PM
Subject: Re: [GMCnet] Steering vibration

Loose bolts at inner CV joint to final drive flange also can cause this vibration. They are the high strength bolts that should be torqued to 75 ft
lbs, IIRC.

Hal Kading 78 Buskirk Las Cruces NM

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> Thank you for the hint. I'll check it out.

From memeory I believe the spec is 65 Ft-lbs. Check the book for sure before you tighten them.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Ken,
Although the X-7525 MM on 3B-3, col 2, para 4 states that the bolts for the flange should be torqued to 75 FTLBS with NEW bolts. In the 18+ years that I have owned a GMC I have NEVER used a torque value that high, as it does stretch the bolts, see explanation in email below. I was told by the folks at Buskirk’s in spring of 1999 that they never went higher than 65 FTLBS. From that point on I used their recommendation on torque value for the axle flange bolts until Jim Hupy posted this email in 2014 as it was a conversation between Karen the person who wrote the manual for the One-ton and I have used that torque rating with the stock axle flange bolts. See posted below

“Quote”

From: James Hupy jameshl296

Subject: Re: [GMCnetl Black List call

Date: September 11,2014 at 10:22 PM

To: gmclist



Karen, I will change what I tell people with regards to torque values on the bolts on the CV flanges. GO with Karen's Recommendations.


Jim Hupy



A little history on why I changed the one-ton instruction torque for the inner CV bolts.
Yes, the manual says 75 ft-Ibs, which is a lot. It also says you can't re-use the bolts, which makes sense
given this very high torque. I installed ours to 75 ft-Ibs originally, and had that torque in the instructions.
Then, when we had to replace the engine at Manny's house, he complained they were torqued too tight (we had to

undo the axle to clear the oil pan to get the engine out...) So, I started double-checking,
talked to Ken H, did a little research. Both Manny and Ken said 75 ft-Ibs is too high and they never do them that tight.
The various technical docs I found backed them up.



As a result, the one-ton kit instruction now says the following:

"Apply loctite to the inner CV joint bolts and torque them to 55-58 ft Ibs.

(The manual states these should be torqued to 75 ft-Ibs and replaced with new ones if they are removed. However, that exceeds the recommended torque for ASTM Grade A574 bolts, which are stronger than Grade 8.)"



Karen 1975 26’

“End Quote”

This is what I do you’re choices may vary!

JR Wright
GMC Great Laker MHC
GMC Eastern States Charter Member
GMCGL Tech Editor
GMCMI
78 GMC Buskirk 30’ Stretch
1975 GMC Avion (Under Reconstruction)
Michigan

>

>> Thank you for the hint. I'll check it out.
>
> From memeory I believe the spec is 65 Ft-lbs. Check the book for sure before you tighten them.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
 
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