Grain truck two speed

notjustair · Nov 30, 2018

I can?t seem to find a new electric shift motor for my 1958 GMC 370 grain truck. The old one is hit and miss at best and I?ve just got it stuck in the high side right now. Since I still use it for some heavy loads I need the low side.

Has anyone found a replacement for the late 50?s GMC trucks with 12 volt shift motors? Is there a newer style that will bolt up to the old rear end? The early 70?s trucks had a three bolt pattern on the rear end for the motor and gearbox but I don?t know if it is the same bolt pattern.

RWT · Nov 30, 2018

Just a thought but have you checked your electrical connections?

I thought that 75 dodge was shifting ok but after I cleaned the connections as I was putting it back together I could tell it was shifting faster.

RT

rusty6 · Nov 30, 2018

Is it an Eaton two speed axle? That is what my IH Loadstar has and I think they were used on a lot of trucks. Its been a few years but parts were available to rebuild whatever it needed at the time. Have you checked the oil in the shift mechanism?

caterpillar guy · Dec 1, 2018

Last 2 speed I drove was vacuum no motor sucked if it had a vacuum leak though.

Bob Bancroft · Dec 1, 2018

If I'm not mistaken, all the two speed shifters I've had were two bolt, and would interchange. I even had an air shifted one, but that's another story! I have driven, but never owned a vacuum shifted one.

The earlier ones had a little plug to maintain a little light oil level. The one I have now has no oil reservoir. It has a circuit board in it with all the little electrical gadgets which burn out. I've had some challenge with that, but it seems to be working now.

It sure seems like there must be an old truck setting around somewhere you could get the whole assembly off.

MarkB_MI · Dec 1, 2018

You shouldn't park it in high gear; if you do be sure and chock the wheels. They can pop out of high gear when parked.

Traditional Farmer · Dec 1, 2018

I had a Louisville Ford that the two speed wouldn't shift all the time,took the motor off cleaned it up,cleaned all the electrical connections,worked like a charm after that.

sms · Dec 1, 2018

As Rusty6 says I used to rebuild mine also, parts came in a kit. If it is working sporatically I would try to disassemble, clean, and lubricate everything and check electrical contacts first, this often helps.

Steve@Advance · Dec 1, 2018

I would go into it first, check all the connections, see why it is intermittent.

Usually a bad motor will have signs of burned insulation. Could be as simple as a broken wire, stuck brushes.

notjustair · Dec 1, 2018

Forgot to add a few things. The brushes wore completely out - like got so short they came out of the holders. I robbed brushes from a wiper motor and can get it to work on the bench about 50 percent of the time but the brass collar it rides in on the top end must be worn because it will bind pretty easy. If I find just the right spot for the top cap it will run but you know it will quit just when I get it put back on. I fooled with it and shimmed the brushes many years ago when parts weren?t available then. It?s terminal. I?m not putting it back on just to have it quit in a month.

She won?t roll away parked in gear around here. It?s Kansas. I don?t park anything in gear or set the brake (except in town). I?ve had an old car short out at the solenoid and you wake up to find it cranked itself across the barnyard and stopped against a tree. Lucky on that one.

Bob · Dec 1, 2018

<img src = "http://thumbs4.ebaystatic.com/d/l300/pict/323289180450_1.jpg">

NOT sure what you want... a replacement for the old style Eaton electric axle shift motor itself is readily available, IIRC, the 12 Volt motors were all the same from the late 50's 'til???. (About $85.)

<img src = "https://i5.walmartimages.com/asr/1fe3cf88-0e6b-47c1-a165-4488cd058483_1.cdf7b3c4b4c926d1f44802ce723c1d6d.jpeg?odnHeight=450&odnWidth=450&odnBg=FFFFFF">

The later style of electric shift unit will bolt up to the axle, as well, and they were still a 2-hole mount to the axle. (About $300.)

<img src = "https://d3d71ba2asa5oz.cloudfront.net/40000505/images/120750.png">

ericlb · Dec 1, 2018

any carquest or napa can get you all the 2 speed stuff, they just need a counter person in there that can read a book

JerryCPP(WA) · Dec 1, 2018

Be sure you remove that little metal cover and check the reversing switch. O'Reilly's has them as part # BWD S481. When the contacts get bad, it will cause your motor to go bad.

rusty6 · Dec 1, 2018

(quoted from post at 09:00:10 12/01/18) Forgot to add a few things. The brushes wore completely out
She won?t roll away parked in gear around here. It?s Kansas. I don?t park anything in gear or set the brake (except in town).

I won't leave my IH Loadstar in neutral any more as it nearly ended up in the trees one night. Was in the combine with a neighbour dumping the hopper on my truck when I suddenly saw the truck starting to move. By the time I hurried down the combine ladder the truck had a good head start on me. I found out just how fast I could run in the dark (just fast enough) and I was able to leap onto the running board, get the door open and jam my foot on the brakes before it hit the trees.
The shift motor was sticky on this one for a long time before I fixed it. I'd pull the button into high and jump out and tap the side of the shift motor with a wrench and you'd hear it shift up. Parked obviously. But it was the only way to get into high axle.

Bob · Dec 1, 2018

(quoted from post at 22:48:52 11/30/18) I can?t seem to find a new electric shift motor for my 1958 GMC 370 grain truck. The old one is hit and miss at best and I?ve just got it stuck in the high side right now. Since I still use it for some heavy loads I need the low side.

Has anyone found a replacement for the late 50?s GMC trucks with 12 volt shift motors? Is there a newer style that will bolt up to the old rear end? The early 70?s trucks had a three bolt pattern on the rear end for the motor and gearbox but I don?t know if it is the same bolt pattern.

In addition to what else has been said, make sure the rubber boot/seal that keeps rear end gear oil out of the shift unit is intact.

They tear and then nasty, heavy gear oil gets into the shift unit.

The seals are still readily available.

There's a fill plug on the cover of the (older-style) shift units, when they get troublesome I either take the steel cover off or remove the unit from the axle, (which you have to do anyway to replace the seal if there's axle oil in there), flush out with electrical cleaner, and allow to THOROUGHLY air dry before putting them back in place, or putting the cover back on, then fill them with oil up to the plug hole.

Believe they originally called for 10W oil, not having that at hand, I've used Hygard for years, with great success.

I'ts amazing how much better they shift cleaned out and with fresh, light oil.

modirt · Dec 2, 2018

Don't mean to hijack the thread, but we have the same truck. What we need is an engine manifold. Ours is rusted through.

Any ideas on where to get a better one?

BTW, on the topic of two speed shifters, as a kid going to school in the 60's, I seem to recall all the school buses of the time had two speed shifters. On the gravel roads making deliveries, low side was used. Once loaded and headed for the barn, driver would shift to the high side and get rolling along pretty good. Can't say I'd blame him. We could get pretty rowdy.

Grain truck two speed

notjustair

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RWT

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rusty6

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caterpillar guy

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Bob Bancroft

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MarkB_MI

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Traditional Farmer

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sms

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Steve@Advance

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notjustair

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Bob

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ericlb

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JerryCPP(WA)

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rusty6

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Bob

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modirt

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