[GMCnet] Bolt Torque for drive axle flange (new subject thread)

[John Wright]

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 james...@gmail.com

Subject: Re: [GMCnetl Black List call

Date: September 11,2014 at 10:22 PM

To: gmc...@temp.gmcnet.org

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

> On Jul 16, 2017, at 3:46 AM, Ken Burton <n9...@comcast.net> wrote:
>
> richshoop wrote on Sat, 15 July 2017 17:56
>> 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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[Ken Burton]

When Jared stopped by my place about a week ago he wanted to recheck the torque on those bolts because he had a trans installed a few thousand miles
ago. I said 75. He said the book said 65. He produced a paper copy of the maintenance manual and sure enough it said 65. I did not look to see
what version of the manual he had but the one he had said 65. That is all that I know.

[Emery Stora]

I have 4 Maintenance manuals.

X7425 says 65 lb-ft of torque

X7525 says 75

X7625 refers to X7525

X7725 refers to sections 3B and 3C in x7525.

Also in X7725 it says that the bracket on the driver’s side of the final drive has been eliminated after 1976 production.

Emery Stora
77 Kingsley
Frederick, CO

[Richard Denney]

I wonder if the intention in over-torquing the bolts was to relieve
internal stresses through micro-yielding. This evens the stress across the
bolt and reduces fatigue points. The bolts can theoretically be reused
after that, but only at a lower torque.

Rick "an established technique for bicycle-wheel spokes" Denney

--
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com

[Chris Geils via Gmclist]

Torquing to 75 lb-ft stretches the bolts, so they must be replaced if removed. Under torquing to 60-65 is probably ok, but use loctite!!!
--
Chris Geils - Twin Cities
1978 26' Kingsley w/ very few mods; Headers, Progressive Dynamics 9040, aux trans cooler, one repaint in stock colors, R134a, Al rad, 50k mi

[Johnny Bridges via Gmclist]

I got some hard hex cap screws which have the same contact patch as the 12 pt bolts, loaded them with a spot of blue loctite and ran them to 60-65 ft
lbs. Seems to work.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

[James Hupy]

The new bolts, which are a 12 point 7/16" socket, (special flange head)
5/16" bolt, intended for 1 time use with a very special lock washer are
included with the Dorman package of fasteners for the 1 ton conversion
package as supplied by Manny T. The current recommendation for torque goes
as follows: Chase existing female threads in the companion flange with a
tap, blow out residue with compressed air. Clean all residual lube with
Chem tool, or brake clean, or special loctite solvent, follow with
compressed air. Assemble with blue loctite by hand until lock washers touch
flange, then torque to 55-58 foot pounds. These fasteners exceed S.A.E.
specs for grade 8. Really high quality stuff. I had one coach that I
installed a 1 ton front end in, have the drivers side fasteners loosen and
fall out under way. It turns out that the owner had a transmission replaced
by a shop not familiar with GMC'S, and they did not follow these
torque/loctite instructions.
Do the work once, do it correctly according to specs, and spend your
time behind the wheel worrying about the other drivers around you. JWID.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

On Jul 16, 2017 10:55 AM, "Johnny Bridges via Gmclist" <

[Jim Kanomata]

Like Jim H says, use Blue loc tite and replace the special lock washer. We
stock the exact correct bolt and lock washers.

--
Jim Kanomata
Applied/GMC, Newark,CA
ji...@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502

[Rob Mueller]

Rick et al,

Below you will find a series of emails I sent in a "few" years back regarding these bolts.

Rob

-----Original Message-----
From: Rob Mueller [mailto:robmu...@iinet.net.au]
Sent: Thursday, May 22, 2008 9:37 PM
To: gmclist
Subject: RE: [gmclist] Inner CV Joint to Final Drive Flange Bolts

Rick,

Thanks for you comments.

1) The Allen headed bolts from McMaster Carr are rated at 180,000 psi which also exceeds grade 8.

Allen Head Bolt
Part Number: 90117A255
Minimum Tensile Strength 180,000 psi

Flange Head Bolt
Part Number: 91271A644
Minimum Tensile Strength 170,000 psi

2) I only drilled safety wire holes in one Allen bolt using a cobalt drill bit. It wasn't a problem.

3) I've sent an email to Cinnabar requesting a price for the OEM bolt and washer; I'll post the info when received.

4) I agree; the bolts are not breaking they're loose because they are not torqued to 75 ft lb. I'll bet dollars to donuts people use common Allen wrenches to tighten these when they're laying under the coach and there is no way you could apply enough torque with one of those!

Regards,
Rob Mueller
Sydney, Australia
75 - Avion - AUS - The Blue Streak
75 - Avion - USA - Double Trouble

-----Original Message-----
From: [mailto:gmclist...@temp.gmcnet.org] On Behalf Of Rob Mueller
Sent: Thursday, August 28, 2008 9:56 AM
To: gmc...@temp.gmcnet.org
Subject: Re: [GMCnet] sizes..

G'day,

I stopped by the shop where I buy my nuts and bolts today and purchased several grade 8 Allen Head Cap Screws (AHCS) (3/8" x 24 x 1 1/4") and some grade 8 (8 mm) hardened washers. Eight mm washers were purchased because 3/8" washers were too sloppy a fit.

The screws were manufactured by:

Brighton-Best Socket Head Screw Manufacturing Inc.
1665 Heraeus Boulevard
Buford, Georgia 30518-3383

The washers were in a bin without any manufacturer labels.

Using a small grind stone in my Dremel tool the holes in the washers were increased to a snug fit around the AHCS threads.

The threaded end of the AHCS were machined flat so the over all length (OAL) could be measured accurately.

I've got the whole front suspension system and drive system out of The Blue Streak so the left final drive flange was clamped in a vice using copper jaw liners to protect the splines.

The inner CV joint housing was placed on top of the final drive flange and one of the AHCS was screwed in finger tight to keep them together.

A 0.300 in diameter ball bearing was inserted in the socket head of another AHCS and the OAL was measured with a micrometer (Measurement #1).

A hardened washer was place on that AHCS and it was screwed it into the inner CV joint housing 180 degrees opposite the one already installed without any lubrication.

The 3/8" x 24 AHCS takes a 5/16 Allen wrench. I put an adapter on my torque wrench (McMaster Carr P/N 5274A12 Easy-Read Adjustable Click-Style Torque Wrench 3/8" SQ Dr, 5-80 ft-lbs/5-110 NM Torque Range) and set to 45 ft lb.

The AHCS was torqued slowly keeping my arm at an angle of 90 degrees perpendicular to the wrench until it clicked.

The ball bearing was re-inserted in the AHCS socket and the OAL re-measured (see measurement #2).

The torque wrench was re-set to 75 ft lb and the AHCS was re-torqued.

The ball bearing was re-inserted in the AHCS socket and the OAL re-measured (see measurement #3).

The AHCS was removed from the flange, the ball bearing re-inserted in the socket and the OAL was re-measured (see measurement #4).

Measurement #1 = 1.6160
Measurement #2 = 1.6180 (bolt stretched 0.0020 at 45 ft lb torque)
Measurement #3 = 1.6218 (bolt stretched 0.0058 at 75 ft lb torque)
Measurement #4 = 1.6191 (bolt stretched 0.0031 from new length)

Copper based anti-seize grease was applied to the threads and between the bottom of the head and the hardened washer of a second AHCS and the test was repeated.

Measurement #1 = 1.6097
Measurement #2 = 1.6130 (bolt stretched 0.0033 at 45 ft lb torque)
Measurement #3 = 1.6183 (bolt stretched 0.0086 at 75 ft lb torque)
Measurement #4 = 1.6133 (bolt stretched 0.0036 from new length)

NEW SUBJECT:

Steve Rourke of Cinnabar advised that the OEM bolts P/N 394777 were available for $2.00 each. They also stock the lock washers P/N MS37 at $1.25 ea.

WHAT I'M GOING TO DO:

Twenty four (24) OEM bolts have been ordered from Cinnabar to fit to The Blue Streak and Double Trouble. When they arrive the heads will be drilled for safety wire using a cobalt drill bit. If they fit snugly 3/8" hardened
washers will be used under them; if not 8 MM hardened washers will be reworked. The OEM bolts will be installed using a bit of oil for lubrication.

UNQUOTE

Update:

I received the OEM bolts from Cinnabar and drilled them for safety wire using a 1/16" cobalt drill. Despite going slowly and using lubricant I burned out two drills! The OEM bolts are harder than the hinges of hell! No
I don't know where that is on the Rockwell scale! ;-)

-----Original Message-----
From: Rob Mueller [mailto:robmu...@iinet.net.au]
Sent: Thursday, May 22, 2008 9:37 PM
To: gmclist
Subject: RE: [gmclist] Inner CV Joint to Final Drive Flange Bolts

Rick,

Thanks for you comments.

1) The Allen headed bolts from McMaster Carr are rated at 180,000 psi which also exceeds grade 8.

Allen Head Bolt
Part Number: 90117A255
Minimum Tensile Strength 180,000 psi

Flange Head Bolt
Part Number: 91271A644
Minimum Tensile Strength 170,000 psi

2) I only drilled safety wire holes in one Allen bolt using a cobalt drill bit. It wasn't a problem.

3) I've sent an email to Cinnabar requesting a price for the OEM bolt and washer; I'll post the info when received.

4) I agree; the bolts are not breaking they're loose because they are not torqued to 75 ft lb. I'll bet dollars to donuts people use common Allen wrenches to tighten these when they're laying under the coach and there is
no way you could apply enough torque with one of those!

Regards,
Rob Mueller
Sydney, Australia
75 - Avion - AUS - The Blue Streak
75 - Avion - USA - Double Trouble

[Johnny Bridges via Gmclist]

I set mine wuith a hex socket and my trusty heathen chinese torque wrench. With loctite after chasing the threads with a tap because the shop which
installed the transmission left them loose... or not tightened enough at any rate so I had to replace them entirely. So far no problems... at least
wiith the flange bolts and axles :)

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

[Ken Henderson]

In the midst of all this axle bolt discussion, don't forget that if you
replace the bolts on the left axle with the Manny 1-Ton, you MUST use 1"
long bolts, NOT 1-1/4", as on the original joints and the right side of the
1-Ton. The 1-1/4" bolts will hit the final drive housing on the driver's
side.

Worth a bold note in the instructions you hand to the non-GMC proficient
mechanic, if you do such things.

Ken H.


On Sun, Jul 16, 2017 at 6:21 PM, Rob Mueller <robmu...@iinet.net.au>
wrote:

> Rick et al,
>
> Below you will find a series of emails I sent in a "few" years back
> regarding these bolts.
>

[James Hupy]

That sounds to me like a life lesson well learned. No substitute for
experience. If you put it in the printed instructions, then all that needs
to be accomplished is to get someone to read 'em. Before the work
commences. That kind of knowledge is what makes this GMC community so
unique. I love it. Lots of tricks like this. No one person possesses them
all. What a great group.

Jim Hupy
Salem, Or
78 GMC ROYALE 403