Question on the hydrashift

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skyrydr2
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Joined: Fri Sep 23, 2016 9:27 am
Location: USA, Massachusetts

Question on the hydrashift

Post by skyrydr2 » Mon Sep 10, 2018 4:44 pm

Can you start off in any gear of the hydrashift? (1,2,3 or 4) with range selector in 1st or 2nd? And what about reverse?
Also what powers the hydrashift's hydraulics? Internal pump in transmission or the main pump out front?

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ollek
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Re: Question on the hydrashift

Post by ollek » Mon Sep 10, 2018 6:27 pm

This has been discussed hundreds, if not thousands, of times. You can start of in any range gear 1, 2, 3 or revere), but you MUST have the hydrashift lever in gear one before you let your foot off the clutch pedal. The hydrashift pump is inside the transmission and the pump is not operating if the clutch pedal is down and the tractor is not moving. Hydrashift gear 1 functions without pressure, but all other gears (2. 3 and 4) need hydraulic pressure. If you start driving with the hydrashift lever in any other gear than 1, you will end up in a situation where the pump output slowly increases as the travelling speed increases. The tractor will therefor start off in gear one and the gear box will then change up on its own to the gear selected. This will take some time and the gear box is slipping until the oil supply is big enough for the gear selected. The result is that the gear box multi plate couplings and brake bands will wear out and all O-rings in the box will get hard and damaged because of the heat coming from the slipping clutches. The end result for using the tractor in the wrong way is a expensive repair. It does not matter if you are travelling in forward or reverse, the same apply. The gear box will give you decades of trouble free driving but you have to maintain the tractor correctly and use the box in the correct way.

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skyrydr2
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Re: Question on the hydrashift

Post by skyrydr2 » Mon Sep 10, 2018 11:42 pm

Thanks Ollek, I thought you had mentioned it before. Is there any external pressure tap to measure internal pump pressures on these monsters? And what pressures does it normally run at when in tip top condition?

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ollek
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Re: Question on the hydrashift

Post by ollek » Tue Sep 11, 2018 4:55 am

The connection point for a pressure gauge depends on the model. A normal pressure at 1200 engine revs is a little bit more than 5 bar in gear one and the pressure rises slightly when changing up in gears and the pressure is slightly higher in later (bigger) tractor models. In order to measure the pressure you need some special tools and the tools needed are also dependent on the tractor model. Start off with getting yourself a Workshop manual.

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skyrydr2
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Re: Question on the hydrashift

Post by skyrydr2 » Tue Sep 11, 2018 9:23 am

I don't have a tractor with hydra-shift at present, I was just curious is all. I have seen many for sale and was wondering if they would be a decent machine but seeing how easily they may be damaged, quite frankly scares me away from getting one with the hydra-shift , or at best paying extra for the option.
I can't imagine why the engineers never made it have constant line pressure knowing it could fail if shifting wrong? Hmmm ..And I have a chance to get a nice 1594 4wd but it has the Hydra-shift and one bit I noticed was the shift lever was a vise-grip pliers clamped on the shaft... Me thinks it has issues and the owner broke the original off yanking on it because it didn't work correctly.... well that just knocked 5k off the asking price.....

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bedwards1966
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Re: Question on the hydrashift

Post by bedwards1966 » Sun Sep 16, 2018 7:03 pm

Well I believe the hydrashift was very advanced for its day, and David Brown probably just didn't go far enough to idiot proof the gearbox to the point that it could be driven incorrectly without suffering damage.

Modern tractors still aren't all idiot proof, I see drivers that destroy clutches and gearboxes through ignorance, stupidity or just not caring because they don't pay for the repairs - or a combination of all three. When people won't follow basic principles of driving a machine or simple instructions, it's hard to design something that cannot be damaged.

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skyrydr2
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Re: Question on the hydrashift

Post by skyrydr2 » Mon Sep 17, 2018 10:38 am

My issue is starting all over every time you push in the clutch? Hmmm not good.. especially for someone stacking on a wagon.
I bale around 1.5-2mph so I would be most likely in 3rd range 1 so every time I clutched I would need to shift back to 1st and then up twice to 3rd ?
I can definately see the potential for damage! And on a machine that is 30 years old.. almost a guarentee it is damaged or in need or an overhaul.

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ollek
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Re: Question on the hydrashift

Post by ollek » Mon Sep 17, 2018 11:25 am

Hydra Shift was never built for loader work, David Brown have other models for this type of work. A Hydra Shift tractor is ideal for heavy pulling in the field or on the road. The range gears are mechanical and you can drive or start in any range (1, 2, 3 or reverse) but you have to stop the tractor if you want to change range. The Hydra Shift gears (1, 2, 3 and 4) can be shifted up and down one gear at the time without touching the clutch pedal or stopping the tractor and without loosing drive when changing gear and you have to start driving in Hydra Shift gear 1. The range gear lever is a long stick and the Hydra Shift lever is a short lever on the dash board. The 1212 was introduced on the market in 1971, almost 50 years ago and several years before anyone else had a power shift gear box to offer. And the first so called power shift gear boxes from other manufacturers had only two gears that could be shifted without declutching, Hydra Shift had 4. The lover gear in the MF multipower had no engine brake, a dangerous situation when driving down hill with a big load on the trailer. Yes, the Hydra Shift was very advanced for its day.

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skyrydr2
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Re: Question on the hydrashift

Post by skyrydr2 » Tue Sep 18, 2018 9:45 am

JD had an 8 speed powershift in 1964 and they were and still are very popular but now it is an 18 speed.
I have rebuilt one of these units that was in a JD 540 A skidder . Awesome piece for pulling.
And you could select any gear you like and start off in that gear with out any issue .
It really was the the transmission to have back then but the tractor was big and long and had poor turning but boys would they pull!

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ollek
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Re: Question on the hydrashift

Post by ollek » Tue Sep 18, 2018 11:22 am

The JD you are referring to was a tractor manufactured and sold in the US. Completely unsuitable for farms in Europe in those days. I am talking about European needs and tractor models. I have also later on tested and evaluated the Case 1270 and 1370 tractors. Big tractors, no 4-wheel drive available, too heavy for use on wet land and not at all suitable for the small Scandinavian farms. These tractors also had a power shift gear box, but it din not help.

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skyrydr2
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Re: Question on the hydrashift

Post by skyrydr2 » Wed Sep 19, 2018 1:05 pm

So true Ollek , they were big heavy rigs and not well suited for New England farms either.
You needed acreage for them, dry acreage to be more accurate. In the early 70s they started producing front wheel assist machines over here and that made a huge difference .

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