1947 Dodge 2 ton 2 speed rear end

[Built in America]

We recently put another piece of iron back on the road with our 47 dodge 2 ton.  We’re having difficulty getting the two speed rear end to engage.

 

1. How/when should we be operating the shifter when attempting to engage the rear end gears?  All 5 speeds including reverse sync up perfectly when double clutching, but when lifting the knob that connects to the vacuum line on the passenger side firewall all we hear is the Excelerator increase but gears are not engaging.

 

2. The small Old vacuum line that connected to the speedometer diaphragm is not connected = May be losing back in there. A. Will the vacuum system still work if we plug that line in order to properly connected to a new speedometer in the future?  OR does that line need to be properly connected to the diaphragm on the back of the speedometer in order for the rest of the system to work properly and engage the rear gears?

[Dodgeb4ya]

You should be able to block that speedo vacuum line off.

There cannot be any vacuum leaks in the shift plumbing.

The rear axle diaphram has to be good and receive full vacuum to move the axle shifting arm.

The Eaton 1350 2 speed axles are a very trouble free axle.

Never park the truck with the axle in high range......or you might find it has rolled away.

Edited January 30, 2023 by Dodgeb4ya
Spell check

[47 dodge 1.5 ton]

 After you verify there is no vacuum leak, for shifting technique—recommend keeping a load on the drive train for several seconds before lifting off the accelerator. 
  Welcome to the forum and we love pictures!! 

[Built in America]

On 11/3/2022 at 9:58 AM, Dodgeb4ya said:

You should be able to block that speedo vacuum line off.

Ther cannot be any vacuum lreaks in the shift plumbing.

The rear axle diaphram has to be good and recieve full vacuum to move the axle shifting arm.

The Eaton 1350 2 speed axles are a very trouble free axle.

Never park the truck with the axle in high range......or you might find it rolled away.

Thank you DogeB4Ya!

 

We apologize greatly. Our initial post was one of our first on this Forum and apparently we did not respond correctly.

 

Your insight definitely helped. After further investigation by our team there  indeed was a slight vacuum leak from an old hose that needed replacement and proper clapping.

 

Diaphragm is surprisingly in great shape. At this point it seems like the high gear engages when there’s ample load on the rear end or if we’re going up a steep hill, otherwise it slips back into low gear.

 

Our assumption from other reads is that the 2nd speed in the rear will only stay in high gear so that we can get/stay above 35 miles an hour (what the 47 will peak at when in low gear) when we have a heavy enough load being carried (just not sure what that load requirements is). Does that sound correct?

 

If that’s correct we may look into bolting on extra steel on to either side just inside along the rear frame so that we can trigger the required load weight to get her to stay in high gear for when we don’t have a traditional load on the back; thereafter we can unbolt and remove the temporary load in the event that were carrying an actual load/product.

 

Thoughts?

[Built in America]

On 11/3/2022 at 10:13 AM, 47 dodge 1.5 ton said:

 After you verify there is no vacuum leak, for shifting technique—recommend keeping a load on the drive train for several seconds before lifting off the accelerator. 
  Welcome to the forum and we love pictures!! 

Hey Dodge 1.5 Ton!

 

Man as we apologize below I to apologize for the delay in response. We actually had responded the day of your post but for some reason we did not respond correctly.

 

What you’re saying absolutely makes sense as we learned a bit more about the rear end on these 2 tons and one and a half ton that is up next to be restored.

 

When you say make sure “you keep a load on the drivetrain for a few seconds“ is that implying that we need to actually make sure we’re carrying enough weight on the bed?

 

I know that sounds like a ridiculous question. I can’t imagine Chrysler corporation would design heavy duty trucks to have to carry weight in order to stay in high (2nd) gear and get up to speed above 35 miles an hour.

 

Through some reading and test driving and fixing the vacuum line we can feel that the diaphragm is in good condition, and indeed the rear end will shift into 2nd gear, but only when we are driving up a steep hill or going down a heavy grade (causing the load). This is worth six spare tires loaded on the back bed.

 

Issue seems to be when we’re no longer going up or down a grade we slip back into low gear and need to slow down given the rpms hit above 3,000 and we remain at about 30-35mph.

 

Thank you for the insight!

Edited February 1, 2023 by Built in America

[Dodgeb4ya]

You can always shift into high range with out any load on the truck.

Shift down/ shift up any time any load...shift as shown in the owners manual or shifter instructions...not complicated or difficult.

Down hill shifts...be careful.

[47 dodge 1.5 ton]

No— Just a “drive train” power load. Seems to work better with power and then releasing power for the rear to engage smoothly. Down shifting going down hill is very difficult to keep from getting into a free wheel situation. I try down shifting when I have a chance for any upgrade (causing a little load on the drive train) before needing to switch rear to low range. Around here, you really need to know the roads or it may not end well.

 I hope that’s clear enough to understand. 

Edited January 30, 2023 by 47 dodge 1.5 ton

[wallytoo]

if it is "involuntarily" shifting back into low range, there's probably still a leak in the system.

 

mine will, very rarely, drop out of high range when cruising along, but it does not go into low range when it does that.  a quick stab at the clutch and throttle and it moves right back into high range.  

[Built in America]

On 1/29/2023 at 10:10 PM, Dodgeb4ya said:

You can always shift into high range with out any load on the truck.

Shift down/ shift up any time any load...shift as shown in the owners manual or shifter instructions...not complicated or difficult.

Down hill shifts...be careful.

Thank you!

 

unless I’m getting a bit mixed up when starting out with the rear end in first gear (low) we’re shifting through all five gears perfectly.

Then when we go to pull up on the vacuum line (knob) on the gear shifter in order to engage the rear end into second gear (high) we lose our gears. We do feel 2nd (higher) speed in the rear end engage when we’re going up or down a stealer grade (I’m assuming the downhill or uphill grades are creating the torque or pressure that the rear and needs (like a load).

 

I’m completely guessing though.?

 

When someone says to make sure that we have a good “load”, that mean that we can literally need to make sure that we have more weight on the bed so that the second speed in the rear end feels that load that’s requiring more work to the vacuum lines engaging the second gear once we trigger it?

[Built in America]

On 1/30/2023 at 3:40 AM, 47 dodge 1.5 ton said:

No— Just a “drive train” power load. Seems to work better with power and then releasing power for the rear to engage smoothly. Down shifting going down hill is very difficult to keep from getting into a free wheel situation. I try down shifting when I have a chance for any upgrade (causing a little load on the drive train) before needing to switch rear to low range. Around here, you really need to know the roads or it may not end well.

 I hope that’s clear enough to understand. 

Thank you!

 

Yes that makes complete sense in. We just need to learn to drive this to turn correctly. I believe we’re close to having the technique down but for some reason were slightly off that’s missing placing the Apple load on the drive train that Dan would enable the second gear in the rearThank you!

 

Yes that makes complete sense in. We just need to learn to drive this to turn correctly. I believe we’re close to having the technique down but for some reason were slightly off that’s missing placing the Apple load on the drive train that Dan would enable the second gear in the rear (low) to engage and stay engaged.

 

Recently we’ve been able to feel it engage but then it slips out shortly there after - usually once we take them out for half of the accelerator.

[Built in America]

On 1/30/2023 at 5:52 AM, wallytoo said:

if it is "involuntarily" shifting back into low range, there's probably still a leak in the system.

 

mine will, very rarely, drop out of high range when cruising along, but it does not go into low range when it does that.  a quick stab at the clutch and throttle and it moves right back into high range.  

Excellent thank you.

 

Yes your insight also leads me to believe that our shifting technique is just not on target yet.  Also I’ll have a closer look at the vacuum line just to make sure there’s no leaks and it’s getting apple pressure.

 

I may be able to install a pressure gauge along the line to make sure that it’s always getting the pressure it needs.  We can have a look in the original manual but any idea what  pressure should be seen in the vacuum line for the rear 2nd gear?

[Dodgeb4ya]

I have driven these trucks a lot with out any loads....even with no beds....they shift flawlessly.

Load does not matter as to if the rear axle will shift up or down.

The shift speeds can be a bit quicker or slower depending on road speed, engine speed and truck load.

If the shifting system is in good operating condition these vacuum shift tear ends are fast to shift and definately stay in either high or low range when driving.

Thete are many video's on 2 speed rear end shifting.

You need to be sure all the vacuum lines, rear axle shift diaphram are not leaking off vacuum.

When you pull the button up while say accelerating moderately then let off thr gas for a 2nd or two you should hear and feek the rear axle shift instantly into high range and never drop out of it until the button is pushed down.

The speedo when up or down shifting the rear end should also bounce up or down in speed to match speed with the rear axle shift.

[Dodgeb4ya]

More specific factory info...don't know why out of order..loaded them correctly..

Edited February 1, 2023 by Dodgeb4ya

[47 dodge 1.5 ton]

I like those trucks! Should add to the pictures thread.

[Built in America]

On 2/1/2023 at 12:58 PM, Dodgeb4ya said:

I have driven these trucks a lot with out any loads....even with no beds....they shift flawlessly.

Load does not matter as to if the rear axle will shift up or down.

The shift speeds can be a bit quicker or slower depending on road speed, engine speed and truck load.

If the shifting system is in good operating condition these vacuum shift tear ends are fast to shift and definately stay in either high or low range when driving.

Thete are many video's on 2 speed rear end shifting.

You need to be sure all the vacuum lines, rear axle shift diaphram are not leaking off vacuum.

When you pull the button up while say accelerating moderately then let off thr gas for a 2nd or two you should hear and feek the rear axle shift instantly into high range and never drop out of it until the button is pushed down.

The speedo when up or down shifting the rear end should also bounce up or down in speed to match speed with the rear axle shift.

Once again - thank you.

 

My thought of bolting 1,000 lbs of steel to the inside of the rear frame that could be removed when I do want to stack the bed, so that the high gear will hold is a relief to know we can scrap that attempt.

 

Okay.  We’re pulled all 6 wheels to start the break restor (not sure if we should order shoes, calipers, copper/Nickle lines, etc from DC Classics - but will ask for advice on our post on the breaks). 
 

I’ll plan to recheck the vaccine line. Hopefully the diaphragm isn’t leaking = it’s the original = it’s one piece. Would be a shame to not be able to keep the original.

Many thanks,

Jason with AutoOwners.org

[Built in America]

On 2/2/2023 at 10:48 AM, 47 dodge 1.5 ton said:

I like those trucks! Should add to the pictures thread.

These are beasts to drive, build like tanks, and yes we too are eager to both of them on the road this year.

 

The green 2 ton runs like an ox. Just needs new break set up and the rear 2 speed figured out (likely driver error haha), then we’ll get it to more Cars & Coffees, etc.

 

Red beauty we call her the 47 1.5 ton has some wrenching to do first. Still 6 volt, starter needs rebuilt, generator too, all need tires, brakes, and likely the distributor and ignition coil. Wiring should be easy.  Oh….and like the 3 inches is cow poop and 60 year old farm field mud that caked the entire frame of our green 47 Dodge, Red beauty has some old makeup that needs chucking off yet. Hahaha.

 

Funny thing is we love the fact that we’re smelling 1947 to around 1963 when we work on them both.  We can read history but not often smell it ?.

[Built in America]

On 2/1/2023 at 1:15 PM, Dodgeb4ya said:

More specific factory info...don't know why out of order..loaded them correctly..

Brilliant!

 

We’ve removed and cleaned the filter screen in the vaccine control body (hits HORSE hair…..hahaha that was the best find on this historical masterpiece that we’ve ever found on a restoration), but haven’t pulled the pins and snap ring to check the internal components = will do that tomorrow. HOPEFULLY this and “maybe” just replacing the vacuum lines (original but when testing with soapy water didn’t seem to have leaks) will prove successful. 
 

Will snap some pics and add once we have the control body open.  Added a couple pics of our 47 red 1.5 ton. She’s still “asleep” in the garage waiting for a wake up call hoping this Spring.

 

Many thanks,

Jason

AutoOwners.org

[jsd245]

Hopefully the shift diaphragm is good. On mine the shift diaphragm is ok but the return spring is so badly rusted it sometimes doesn’t return it back to low. I don’t see any way to rebuild these, and I haven’t found any source for a replacement. I have an air diaphragm valve I found I am looking to retrofit . 

[Built in America]

On 2/2/2023 at 10:48 AM, 47 dodge 1.5 ton said:

I like those trucks! Should add to the pictures thread.

Thank you again for the response.

 

Not sure if how we responded prior got through to you but just want to give everyone an update that we finally got this beast to properly shift into high gear.

 

Not sure exactly what triggered it might’ve been the vacuum system after we finished restoring the brake system, or could’ve been a minor adjustment that we made at the vacuum intake point just off the carburetor.

[Built in America]

On 2/7/2023 at 4:08 PM, jsd245 said:

Hopefully the shift diaphragm is good. On mine the shift diaphragm is ok but the return spring is so badly rusted it sometimes doesn’t return it back to low. I don’t see any way to rebuild these, and I haven’t found any source for a replacement. I have an air diaphragm valve I found I am looking to retrofit . 

Thank you so much.

 

The diaphragm seems to be in great condition, the spring was decent we just gave it a good cleaning and wheeling, made some minor adjustments and now it seems like we shift into high gear real nice.

 

Thank you so much for your tips. This  beast is now on the road and running. Just fine tuning the braking system.

[Built in America]

On 2/1/2023 at 1:15 PM, Dodgeb4ya said:

More specific factory info...don't know why out of order..loaded them correctly..

Circling back after while.

 

Just want say thank you for the documents and all of your help.

 

We finally were able to get this beautiful two-ton beast shifting into high gear real nice. Still not certain which adjustment it was that helped us and I think we might still need to make some adjustments to better the synchronize but it is running for power.