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2 speed rear axle


Dunkin
Go to solution Solved by Dodgeb4ya,

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Howdy,

 

I have what I believe to be an Eaton 2 speed rear axle on my truck, but I wanted to know if anyone could help me identify what model I have.  The only markings I have been able to find are in one of the photos I've attached.  

 

I am having complications staying in hi gear and need to know what model I have in order to hopefully find a resolution.  I believe it might be a vacuum (or lack of) related issue.

 

Thanks,

Roman

1947 - WHA48 Dodge 

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  • Solution

Your 2 speed is a model number 1350 Eaton.

You need good strong vacuum at the shift diaphram to keep it in high range.

You could wire the shift lever into high range to be sure it will stay in high range and know your issue is in the vacuum supply circuit.

 

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Thanks Dodgeb4ya for decoding my axle.

 

When you say "shift diaphragm" are you referring to the one on the axle or are you talking about the shifting valve in the engine compartment that sits on the firewall?  As a side note, there seems to be a stronger vacuum sound at the valve when the hi/lo shifter is only pulled up half way.  Do these shifting valves go bad?   

 

So I will use some bailing wire to hold the shift lever at the axle in high range and if it doesn't disengage at full speed/rpm, then I might have a vacuum leak somewhere.  Possibly the diaphragm has holes in it.  I know you can purchase a new diaphragm for these, but can I replace it myself or do I need to send it off to someone more experienced in rebuilding these units?

 

Since I will only be using the truck to drive around town or on the farm, then could I just leave the shift lever in high?  I was under the impression that the low gears were mainly used under a heavy load. 

 

Thanks a bunch,

Roman

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No you cannot wire the rear axle shifter lever permanently In high range position.The operation of this axle needs to work as designed. I am pulling back on wiring up the axle shift lever as dangerous for a person not familiar with a 2 speed rear axle operation

...a possible run away situation could happen.

The whole system needs to be checked for any vacuum leaks(hissing). Speedo adapter diaphram,rear axle diaphram, all vacuum tube/ hose connections. Make sure the shift cable fully and correctly opens and closes the control valve on the firewall to admit full vacuum to the axle shift diaphram with the shift control button fully pulled up...causing  the axle shift lever to move forward into high range.

BTW This thread really needs to be in the truck section?

 

 

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I will just have to perform the ole smoke test on this beast and see what I can come up with. 

 

I agree that I should've started this thread in the truck section.  Unfortunately I do not know how to move it now, but maybe I can get an assist.

 

Thanks for your input Dodgeb.

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  • 5 months later...

Hello,

 

Can anyone tell me if the shift diaphragm is rebuildable?  I am close to completing my truck and the only item I have  yet to seriously address is the 2 speed rear end.

 

Regards,

Roman

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MoPar Part # 1191686...listed as the only part number for Eaton 1350 2 speed shifter assembly in the 1948 to 53 DT parts books.

AMS Obsolete supposedly has it ....only as the complete assembly as only way the part was sold new.

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I am talking about the rear end vacuum  shifter diaphram assembly ....on the rear end.

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I noticed that once I looked at the parts list description, so I shot them an e-mail to check if they had one for sale.  I was also thinking that the vacuum valve that sits on the firewall might have something to do with my problem and I asked them about that unit as well.

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Don't throw parts at it...

Run the engine...pull the red shifter button up or down...have a helper watch/listen for movement at the rear axle shifter lever and diaphram..

If there is some tiny or more movement and or hissing at the rear axle shift  lever as the shift button is pulled/pushed up and down.... then that means the control valve ,shifter cable and vacuum lines are mostly working.

Next step..hook a vacuum gauge up the the rear axle shifter hose...do the same test pulling up and pushing down the shifter button watching the vacuum gauge. Gauge should show 15 or more inches of vacuum with the button pulled up and zero with it pushed down.

If it works vacuum wise and the axle still does not shift into high...it's either a bad axle shift diaphram or internal axle issue.

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I hear ya!!  It shifts into high, but as the engine reaches max rpm regardless of gear, the rear end loses vacuum and drops into low.  Once I back off the gas pedal for a second it will switch into high gear.  As long as I don't max out the engine too much it will stay engaged in high. 

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 Vacuum is bleeding off in the one way check valve. 

Located in the firewall control valve.

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Oh wow, great information Dodgeb4ya.  I will go thru the process and see where it takes me.  I've had a sneaky suspicion that the issue has been in the vacuum shift, but didn't have any service instructions.  You must have quite the library of service manuals.

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Yeah,

I have a lotta MoPar paperwork?

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Not sure what to think of this, but I drove my truck today to have a rubber floor mat installed and I had no issues in high gear.  Is this wishful thinking?

Edited by Dunkin
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