How to weld axle tubes on GM 8.5" 10-bolt

[Kevin Callahan]

Brian and I recently welded our 8.5” 10-bolt GM axle tubes to our differential housing per the popular recommendation. Since the differential housing is Nodular Cast Iron and the axle tubes are steel, the welding is not particularly straightforward. We did some research beforehand to ensure we did the job correctly. The result of this research yielded the following weld schedule, which was what we used:

Weld process : TIG (Gas Tungsten Arc Weld)
Weld Current: 165A (this was a measurement taken during the weld)
Shield Gas: Pure Argon (approx 25 CFH)
Electrode diam: 3/32”
Preheat Temp: 400-600degF
Interpass Temp: 400-600degF
Preheat Method: Rosebud tip on Oxy-Acetylene torch (Victor 315C torch handle)
Filler Material: FM-99, (meaning 99% Nickel)
Filler Rod diam: 3/32”
Filler Data: 71,000 psi ultimate tensile Strength and 12% Elongation See here for details.

Post weld treatment: Mechanical peening and slow cool (recommend 100 degF/hr but we were only able to achieve 200 degF/hr using insulation blankets)

Step 1) The differential was stripped of all its parts (including bearing races and seals). I don't know if this is mandatory, but we did it anyway.

Step 2) Grind all the rust and casting scale off the differential housing and the axle tubes. Make sure to grind right down to clean material leaving no corrosion pits or casting pores. Notice in the illustration below that the differential housing had to be ground concave in order to get right down to the intersection of the axle tube and the housing since the grinding wheel usually has a rounded edge.

This is a picture of the ground area:

This picture shows how clean the surfaces needs to be.


Step 3) Since the differential housing required pre-heating and interpass temperature control, we wrapped the differential housing in ordinary fiberglass house insulation (with paper batting removed). The housing stayed wrapped the entire time, from before pre-heat until after cool-down.

Step 4) Preheat the cast iron differential housing using a broad flame a few inches inboard of the steel axle tubes. This is best done with a “rosebud” tip as shown in the picture below. The axle tubes did not end up requiring direct heating with the torch since they were in such good contact with the housing. The proper pre-heat temperature was measured by special temperature indicating crayons. The crayon is wiped on the surface to be measured and it melts if that surface is above the crayon’s indicated temp. One well known manufacturer in the welding industry has a product called Tempilstiks. See here for details.

Here is a picture of the preheat temperature measurement:


Step 5) The first welds were made in three places, about one inch long and evenly spaced around the axle tube. Then, these segments were joined to form a complete weld pass followed immediately by mechanical peening. The peening was accomplished using a three pound sledge and a piece of steel with a rounded nose as seen in the picture below. This is done to place the weld fillet into compression, reducing the risk of cracking during cooling. The second pass completed the weld and was also peened immediately.

Here is the tool used to peen the weld:


Step 6) The differential housing was heated again to the maximum pre-heat temperature. Immediately after heating, the entire rear end was wrapped in fiberglass insulation and allowed to stand for four hours.


Time to pull some wheelies!

[ThaDex]

Wow! That was a very nice how-to. Can you use a mig to weld it? I'm not sure if you can get high nickel wire for migs?



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ThaDex
1981 Z28
1978 LT

[79ZED]

Thanks Keven and Brian, excellent info and pictures.

I'm keeping this on file to make sure I get mine done right!

Thanks again!

John
79Z28

[camaro71/holland]

This is why I love this site!!!

Great info guys!

In my opinion, there should be a 'how to' topic where you can't ask questions, but just put info & pics like you did guys.
It would help alot of us and save standard questions.

Thanx again, David

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355cui,
SportsmanII,
Crane 222/234 @ 0.050,
TH400, B&M2400
It's what you know that makes you go!

[POS71RS]

Can the admins archive this please???
Awesome how-to, and pics to boot. We all thank you, and generations of, "how do I...?" to come.
Mike

[big gear head]

Kevin,
That is a much better job than most people have done. I know of many people who just took their car to the muffler shop and had them weld it with a MIG and cheap wire. This is not the way to do it. I have used my MIG to weld them before, but I used a high nickel wire. I still don't like doing it that way. I ise nickel rods and stick weld them now. I think I'll look into that nickel wire that you used and start TIG welding them. Great job.

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'69 RS/SS396 Pro Street
427 4 speed 9"
Byars Performance
High Performance Drive Train Parts And Service
www.lubedealer.com/biggearhead

[rscamaro73]

<font face="Arial,Verdana" size="2">Originally posted by POS71RS:
Can the admins archive this please???
Awesome how-to, and pics to boot. We all thank you, and generations of, "how do I...?" to come.
Mike</font>

Done deal.....

Damn good article....

Awesome job, but when you said "The peeing was accomplished using a three pound sledge and a piece of steel with a rounded nose as seen in the picture below" what exactly do you pee on?

[Kevin Callahan]

Thanks everyone. Hah! Good catch 73454! How funny... I guess it's NOT clear from the picture where the peeing should happen. Maybe I should have another pictrue there.

ThaDex... You had asked about MIG wire for cast iron: It looks like Nickel wire is avalable for MIG welding. Look here for further information. It looks like their product for cast iron is "Techalloy 99" with a datasheet shown at the bottom of their website page. I have not welded cast iron with a MIG, so I can't really give any good tips or info.

Here's a pic of the TIG welding anyway just for kicks:


[This message has been edited by Kevin Callahan (edited April 28, 2004).]

[Louich]

thats real nice...when you coming to do mine???

[Gary S]

If you have access to the kind of equipment and skills that Kevin showed here, do it his way, but if you do things yourself in your own garage and are limited like most of us, don't be imtimidated by this project. My Sons and I have been welding rearends ourselves in the garage using only a 110V Lincoln MIG wirefeed welder and standard cheap wire. So far, we have done 4 rearends. Two of them have a number of years on the road now as daily drivers, and the other two are in performance cars where strength matters to handle the power.

[yody]

I used a 110V mig also and my welds look exactly the same as abover. i had my rearend burned and sandblasted. Don't know if it will really work but it looks like there was good penetration. Seems a little complicated to just weld the tubes! little overkill but whatever works!
bet that fiberglass smelled good burning!
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http://geocities.com/codybouc/firebirdpage.html

[This message has been edited by yody (edited April 29, 2004).]

[big gear head]

The reason for using the nickel wire is because steel wire doesn't blend well with cast iron. It may look fine, but it could actually be broken away from the cast iron. The nickel will blend with the cast iron and not break away. I have had some training and experience welding cast iron and I have seen what happens when mild steel rods or wire is used to weld iron. It looks fine but breaks off easily. Don't get me wrong, I'm not saying that everyone who used a MIG is going to have problems, but the best way is to use the nickel wire or rods.

------------------
'69 RS/SS396 Pro Street
427 4 speed 9"
Byars Performance
High Performance Drive Train Parts And Service
www.lubedealer.com/biggearhead