MY 1969 PETE ON YOUR STEPDECK? SHOT IN THE DARK!!

BIGZILLA · Mar 16, 2016

Zeviander said: ↑

That's a profile pic if I've ever seen one. BAMF
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Done. But I was thinking of changing it to this:

BIGZILLA · Mar 16, 2016

ColoradoGreen said: ↑

You have a 13x4. No larger than a 12713 or so on the 13-speed, without seeing a data-plate or even a box, it's near impossible to say the precise type of 4-speed you have.

Post a photo of the driveshafts.

Being a 13x4, the truck is set for heavier work, it may have had a winch at some point or another, as the 4-speed would allow for a power-tower, or an auxiliary-mounted PTO that you could leave the mainbox (13-speed) in gear and control the speed (be careful doing this).

The shift pattern for the 4-speed should be an H-pattern with a horse-collar, like so:

DU (1) OD (4)
|_____|
| |
UD(2) Dir (3)

Gears are DU: deep-under (1st), UD: Under-drive (2nd), Dir: Direct (3rd), and OD: Overdrive (4th)

You can find out, without a data-plate, whether or not it's a proper deep-reduction deep-under box by shifting from deep-under to underdrive. If it has the ultra-low deep-under (2.37:1) hole it'll be about a 1000-rpm shift. If it's a relatively shorter shift, it's likely a progressive auxiliary.

Because your's is mated two a 13-speed, it's most useful to effectively, if doing heavy work, to treat the auxiliary as a two-speed rear, shifting between underdrive and direct.

Deep-under, whether in this set-up or a 6x4 like my truck, you don't use once you're out of it. It's strictly an ultra-low starting hole gear. If you were in a higher gear in the main, trying to downshift to the deep-under hole would be the equivalent of dropping two gears on the 13-speed.

There's two problems with utilizing the overdrive gear all that much with your set-up: bearing-speed and driveshafts (this is why it'd help if you posted a photo of the driveshafts).

Assuming your 13-speed (the mainbox) is a 12713, it's going to have an 0.81 overdrive gear, more than likely, the overdrive in the aux will be between 0.90 and 0.80, giving a compound overdrive gear in the neighborhood of 10% higher than modern 13-speeds (top two OD, 0.81 and then 0.73).

That means two things: the bearings, and the driveshaft, will be spinning immensely fast in overdrive. If this was a retrofit, which I imagine it is, then the driveshafts might not have been updated. I wouldn't imagine you have anything heavier than standard-wall 1210, MAYBE 1410 driveshafts. The lighter driveshaft won't like spinning that fast, as you'll be looking at in excess of 3000-rpm in the big hole at 2100rpm.

The bearings in the auxiliary will be spinning at immense speed, as well, in that hole.

The backside, generally you don't want to utilize OD in the auxiliary as much when you're in underdriven gears in the main (anything lower than direct gear). Here and there won't kill it, but, a sharp torque load from the engine with the main (13-speed) in a lower gear where it's multiplying torque could potentially wreak havoc on the auxiliary if it's in OD. If you're going to put it in OD in the aux while in a lower mainbox gear, don't just stand on the throttle, walk into it (you should always drive this way anyway). Direct gear on the main (top hole, splitter in DIR) and the OD on the aux won't notice a thing, no multiplication of torque.

Make sure you square on the corners on the horsecollar shift (2nd to 3rd), if you don't you'll bind the linkages to the auxiliary, and you'll need a bar to pop them loose. Considering the age of the tractor, the linkages are likely worn, meaning it's more susceptible to this, square the corners like you're drawing three sides of a square.
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Well I will have to read that again and again after my coffee, but I'm starting to get a grip on this, I think. I really appreciate the education and the advise. I will try to locate, clean and photograph the data plates. I see why....

TripleSix said: ↑

They say his name with reverence and awe. The mighty Colorado, Dean of 2 stick trucking.
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johndeere4020 · Mar 16, 2016

The drive shaft speed will be determined by the rear end ratio. Irregardless of what the ratios of everything in front of the shaft the shaft turns the same speed to turn the rears based on the rearend ratio. Pull all the transmissions and put in a 9 speed direct and the driveshaft will spin the same speed. The only way to change that is changing the rears.

BIGZILLA · Mar 16, 2016

johndeere4020 said: ↑

The drive shaft speed will be determined by the rear end ratio. Irregardless of what the ratios of everything in front of the shaft the shaft turns the same speed to turn the rears based on the rearend ratio. Pull all the transmissions and put in a 9 speed direct and the driveshaft will spin the same speed. The only way to change that is changing the rears.
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OK, I'm a newb, but won't the forward drive shaft spin at a different rate than the shaft between the drives? otherwise what's the use this:

BIGZILLA · Mar 16, 2016

Let me clarify, The decisions I make in that cab with this combination, regardless of gear ratios in the rear end, can and will affect the rate at which the rear drive shaft spins and the amount of stress I put on it. Correct? This is just my logical mind getting the best of me, definitely not speaking from experience.

johndeere4020 · Mar 16, 2016

BIGZILLA said: ↑

OK, I'm a newb, but won't the forward drive shaft spin at a different rate than the shaft between the drives? otherwise what's the use this: View attachment 132558
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No they turn the same speed, both rearend are (or better be) the same ratio so they'll spin the same speed. That short shaft is just passing through to turn the rear diff.

johndeere4020 · Mar 16, 2016

BIGZILLA said: ↑

Let me clarify, The decisions I make in that cab with this combination, regardless of gear ratios in the rear end, can and will affect the rate at which the rear drive shaft spins and the amount of stress I put on it. Correct? This is just my logical mind getting the best of me, definitely not speaking from experience.
Click to expand...

No the rear end speed and driveshaft speed will be determined by the rearend ratio and tire size. For example a 4:30 rear with a 11r24.5 will require the same amount of revolutions to turn the wheels regardless of what's turning them. Pull those transmissions and put a 5speed Mack in and it still takes the same revs to turn the same 4:30's with the same 11r24.5's. Look at it this way, the only way to change the speed of the rears is to spin the driveshaft faster or slower, so at any given speed the only way to change the input share speed is to change the rearend ratio.

BIGZILLA · Mar 16, 2016

johndeere4020 said: ↑

No the rear end speed and driveshaft speed will be determined by the rearend ratio and tire size. For example a 4:30 rear with a 11r24.5 will require the same amount of revolutions to turn the wheels regardless of what's turning them. Pull those transmissions and put a 5speed Mack in and it still takes the same revs to turn the same 4:30's with the same 11r24.5's. Look at it this way, the only way to change the speed of the rears is to spin the driveshaft faster or slower, so at any given speed the only way to change the input share speed is to change the rearend ratio.
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johndeere4020 said: ↑

No they turn the same speed, both rearend are (or better be) the same ratio so they'll spin the same speed. That short shaft is just passing through to turn the rear diff.
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You missed my point entirely. I know both rears are the same gear ratio.

Let me put it this way:
What is this between the front drive shaft and the front drive axle?

johndeere4020 · Mar 16, 2016

BIGZILLA said: ↑

You missed my point entirely. I know both rears are the same gear ratio.

Let me put it this way:
What is this between the front drive shaft and the front drive axle? View attachment 132560
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Sorry I missed your point, I'm not familiar with that particular rearend one of the olde guys will have to chime in. But it's most likely the power divider. If it is it just locks your rearends together.

BIGZILLA · Mar 16, 2016

johndeere4020 said: ↑

Sorry I missed your point, I'm not familiar with that particular rearend one of the olde guys will have to chime in. But it's most likely the power divider. If it is it just locks your rearends together.
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I'm sure they will. And I'm sorry if that came across as sarcastic.

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