2 Speed Rear End Problems - Strange Noise and Oil Leak

Lanse · Mar 1, 2017

Morning everyone! So, I took my 1984 Ford F700 (4 speed with 2 speed rear end) for a drive this morning, and almost as soon as I'd left, I noticed a strange and loud (louder
than the engine) sound coming from its rear end, it sounded like a ratchet being spun quickly! Whats strange is this only happens while shifting between its 2 speeds,
occasionally while downshifting, and/or coasting when between transmission gears.

I wasnt sure what to make of this, but when I got home I noticed that it had started leaking oil at the driveshaft seal on the front of the axle assembly, where it hadn't before.

Any ideas on what it could be? Other than that, it shifts perfectly and previously hadnt leaked a drop of oil. A few months ago, I drained the rear end (everything looked
normal), and refilled it with oil (90wt IIRC).

Any thoughts? I'm guessing something bearing related but I've never worked on one of these...

stonerock · Mar 1, 2017

treat your two speed like a unsinkranized [spelling] trans, your not shifting fast enough and its grinding between gears. shift your two speed with your gas petal not your clutch. timing is everything you will get used to it

Lanse · Mar 1, 2017

Okay, I'd been shifting it with the clutch. What about the strange whirring noises/ratcheting sounds and oil leak? Did I smash something in it?

John Deere D · Mar 1, 2017

Is the sound more prevalent when Differential is under power ( Engine is accelerating) or is the sound more prevalent when Differential holding back (Engine is not accelerating)?

With TIRES blocked and Transmission in Neutral try rotating the drive shaft CCW>CW.....

Jack one set of Duals off the ground rotate Duals CCW >CW listening for any thing suspicious...

Bob...

stonerock · Mar 1, 2017

ngatching sound is because your not on the gas fast enough after shifting, your grinding the two speed gears

stonerock · Mar 1, 2017

ratching sound is because your not on the gas fast enough after shifting, your grinding the two speed gears

Bob · Mar 1, 2017

It shifts using a shift collar with notches at each end, that match up with another set to the right or left, depending upon if you are shifting up or down, as the other poster said, it's basically an unsynchronized transmission, and you have to match the engine speed, ground spreed and main transmission gear up to which way you are going with the two-speed or it won't be able to "catch" and you will hear that ratcheting sound.

Typically, there's 10W oil in the actual shift mechanism, and heavy gear oil in the rear axle with a rubber boot/seal where the two-speed attaches to the axle. If that boot/seal tears/fails heavy gear oil gets in the two-speed shift unit, making for a slow shift that aggravates any tendency to miss a shift/grind.

Mite want to take a look at the two-speed unit and open up the little fill plug and see what's in there, light oil, no oil, heavy oil, or watery oil. At the very least it would be a good idea to drain it and put in fresh clean oil.

BTW, did you get the taillight issue figured out, maybe I missed the resolution to that?

showcrop · Mar 1, 2017

When I was kid I lived on a road with two active sand quarries a half mile down the road. Now back then two speed rear axles were pretty common in smaller dump trucks and most of the time most of the trucks hauling would make at least one down shift on the hill near my house, and it seemed like most of them made a ratcheting noise when they shifted the rear axle.

pete 23 · Mar 1, 2017

When you shift, it winds up a spring and when you take the load off the speed it was in , that spring pulls collar out of that speed and attempts to match the teeth on the other end for other speed. Learn how and it will go slick as snot. I never did get it down pat but I really only worked on them and then road tested. Rode with a few drivers that were really good at shifting and some that were not. Also, there is a set of contact points on each end of the motor wind up mechanism so it breaks the circuit to motor once that mechanism reach's the end. When you pull switch for other speed, the motor reverses and runs until points are opened on the other end breaking the circuit .

fixerupper · Mar 1, 2017

When I was a kid the school bus was a 1954 or 1956 Ford with a 2 speed, probably vacuum 2 speed back then. The regular driver could shift the two speed without grinding but a substitute driver didn't have 'the touch' with the gas pedal and would grind it every time.

BarnyardEngineering · Mar 1, 2017

Hey Lanse, did you figure out what was causing the truck to sound like a bulldozer on cement?

In your videos, last I saw on that subject you thought the transmission was shot, and I haven't seen any updates on that front. All the recent dump truck videos, I can still hear it clanking away when you move it around.

Donald Lehman · Mar 1, 2017

Two speed rear end shifting procedure: Shifting from the low range to high- At the same instant you pull the lever, let up on the gas, pause a bit, and then down on the gas. Shifting from the high range to low-Push shift lever, let up on the gas and right back down again with no pause. As mentioned below, the grinding noise means you are not at high enough rpms when you are shifting up. Don't ever remember having to repair any of our 2 speed rear ends, but I could be wrong. been a few years. (40 at least) Remember replacing outer wheel bearings ad seals a few times, and a couple of broken axels, but no two speed work. On very long, hard pulls, I remember Pop using the clutch when shifting the two speed down, but only rarely.

showcrop · Mar 1, 2017

(quoted from post at 19:12:25 03/01/17) Two speed rear end shifting procedure: Shifting from the low range to high- At the same instant you pull the lever, let up on the gas, pause a bit, and then down on the gas. Shifting from the high range to low-Push shift lever, let up on the gas and right back down again with no pause. As mentioned below, the grinding noise means you are not at high enough rpms when you are shifting up. Don't ever remember having to repair any of our 2 speed rear ends, but I could be wrong. been a few years. (40 at least) Remember replacing outer wheel bearings ad seals a few times, and a couple of broken axels, but no two speed work. On very long, hard pulls, I remember Pop using the clutch when shifting the two speed down, but only rarely.

There is no reason at all to let up on the gas "the same instant " as you pull the knob. You "preselect" as the instructions on the plates say, then just like the auxiliaries on an 8LL or on an eighteen speed, you actuate the shift by releasing the gas pedal.

used red MN · Mar 2, 2017

Nobody addressed your question about the rear end leaking at the "driveshaft seal" or properly named "pinion" seal. So you have to determine if loose pinion bearings are a contributing factor. Pull truck on a level hard surface so you can crawl under it. BLOCK THE WHEELS real good take the truck out of gear and turn off the emergency brake. Firmly try to move the pinion yoke up and down. There should been minimal slack like less than the thickness of 4-5 sheets of paper. If that is tight the seal has went bad. You will need a large impact and most likely a puller to remove the yoke to change the seal. If the seal surface on the yoke is grooved badly you will need a speedi sleeve to repair that. If the bearings are loose then you have a much larger job on your hands.

2 Speed Rear End Problems - Strange Noise and Oil Leak

Lanse

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stonerock

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Lanse

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John Deere D

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stonerock

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stonerock

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Bob

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showcrop

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pete 23

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fixerupper

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BarnyardEngineering

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Donald Lehman

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showcrop

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used red MN

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