An idea for cold hard starting 400 series

[woodlandfarms]

So as for penance for getting the cool handmade tractor seat from the wife. I have been sent to eastern washington to spend the holiday with her family. At this point I am very positive the seat is not worth this but I digress. Her BIL has a new hobby which is restoring old garden tractors.

So he was starting up his Cub Cadet and he was pulling on a lever under the seat. I asked him if that was a belt release and he said no, it is a pressure release on the tram pump. I had never seen this before, or even heard of it. Hopefully JJ or someone who is well versed in Hydraulics can weigh in. On his tram, there were two button valves. And I was unclear if the valves were pushed or pulled as the tram he demod for me was a spare sitting on a bench.

But it got me thinking. I do not have a cold start issue, but I do have a tram valve I need to release the pressure on to tow. Are the 400 series the same? Would this make a differece in starting? Not sure on any of this but it seemed like an idea. I can't go any further on explorations as I do not have a 400 series....

 

[MossRoad]

There is a tram valve on the 400 series for emergency towing, only a short distance at very slow speed. I'm guessing winch speed, as in tow truck. Its a nut that you have to turn with a wrench. It would be nice if there were some sort of relief for starting. But its not just the tram pump. Its also the main PTO pump and the steering/FEL/AUX PTO pump. So there's three pumps on the 400 series motor. That's quite the load on that little starter.

On that note, I've also seen a clutch for a Kohler engine where you can disengage the drive shaft of the engine. That would be sweet! But the only one I ever saw was over a grand, and it would add to the length of the driveline by about 10", so it probably wouldn't fit in the tub the way the current machines are set up. Don't know if they are made anymore.

 

[woodlandfarms]

so you should talk with Terry as I do not know the 400 at all but When I had a tram issue, I asked him about your notes. He said to me that the speed should be slow but tow it as far s you want. Releasing the tram valve allows the pressure from the wheel motors to flow through the pump without creating friction, pressure, yada yada. Speed was an issue, and on my machine you have to pump up a brake system to create pressure to release the brakes. If you turn the wheel a lot being towed, the pressure drops and you have to pump up again.

But to my OP, The tram pump is the pump you have the most pressure on if I am not mistaken (it is powering a closed loop system) The PTO pump is dumping directly back to the tank, and the same with the FEL circuit. Yes, you are turning thick oil but do you think it would helps not having the tram engaged?

THat would be the test. Go out one cold morning and release the tram pump and see if it makes any sort of difference.

 

[joshlee]

That has me curious, but I just sold my 425. This 1430 starts really well in cold weather.

 

[MossRoad]

On my 2001 model year PT425, that valve is on the side of the tram pump...

Just opposite of here....

And about under that big bolt head behind the left corner of the gas tank in this picture...

There's no easy way to get to it, but certainly worth a try.

But, as I recall, its a screw that you turn out to release the pressure, then turn back in to restore pressure. I can't recall if there's a locking nut around it or not. I'll have to look some day.

Hmmmmmmm......................Now you got me thinking, and that's downright dangerous!!! :laughing:

If there is no locking nut, all it would take is some steel rod stock, a couple small U-joints, a couple bearing blocks, a spare valve screw to experiment with and you could probably weld some rod stock to the screw head, and extend it out to a very reachable place with a series of U-joints, bearing blocks, rod extensions, and weld a piece of rod stock at the end for a T handle to turn it. Hmmmmmmm.............

Guess we should start with opening the valve before starting the engine to see if it does any good before going through the hassle.

Is there any harm in opening that valve and starting the tractor with the engine? Will it cause any problems with the tram pump bypassing pressure? Stuff like that....

 

[BobRip]

Can't believe it took this long to think of this. It should release the tram pump precharge pressure. That has got to help some. Correct me if I am wrong.

 

[MossRoad]

Can't believe it took this long to think of this. ...

We on this forum are the braintrust of the Power Trac world.... 15 years for a solution!!! :laughing: :laughing: :laughing: :laughing::laughing::laughing:

 

[Marks481]

Is there any harm in opening that valve and starting the tractor with the engine? Will it cause any problems with the tram pump bypassing pressure? Stuff like that....

Maybe somebody should give Terry a call... that is an expensive pump to replace.

I thought the tram pump didn't actually move any hydraulic fluid until you pushed on the pedal, being a variable displacement pump which displaces 0ci and is essentially just a rotating plate until you wanted to go somewhere. I thought the bypass was for fluid to flow around the pump in a circuit so the wheels would move when the pump wasn't spinning. I don't think bypassing that pump will make a difference for starting since the pump doesn't do any work with the tram peddle in neutral. I think the main load is the other pumps which are actually recirculating cold hydraulic fluid.

 

[woodlandfarms]

To get an idea of what I was on about, look at this video around the 7 minute mark. He takes out the valves in question. There are other videos of htis valve in operation...

Cub Cadet 129 ported hydrostatic transmission - YouTube

 

[MossRoad]

Maybe somebody should give Terry a call... that is an expensive pump to replace.

I thought the tram pump didn't actually move any hydraulic fluid until you pushed on the pedal, being a variable displacement pump which displaces 0ci and is essentially just a rotating plate until you wanted to go somewhere. I thought the bypass was for fluid to flow around the pump in a circuit so the wheels would move when the pump wasn't spinning. I don't think bypassing that pump will make a difference for starting since the pump doesn't do any work with the tram peddle in neutral. I think the main load is the other pumps which are actually recirculating cold hydraulic fluid.

That's worth a long discussion, for sure.

As I understand it (JJ cringes when I say this :laughing: ), the two PTO pumps put out high pressure. The main PTO pump pushes it through the electric diverter valve and back to the tank. Its high pressure between the pump and the diverter valve, then low pressure back to the tank, no? Same thing with the AUX PTO/FEL/Steering pump. Its high pressure between the pump and steering valve, high pressure out of the power beyond port on the steering valve, and high pressure from that power beyond port to the 3 spool FEL/AUX PTO valve body, then low pressure back to the tank. So I would have thought that as soon as you put a few cranks on the starter, its building up pressure in those two hydraulic PTO pumps. Its also building up pressure on the charge pump inside the variable volume tram pump. The swash plate in side the VVP is neutral, so not pushing any fluid, but the charge pump is building pressure.

Still, it would be worth some investigation to see if we can open the bypass port on the VVP when starting and if that can't cause damage, then give it a try to see if there's any difference in cold starting.

So how would we measure difference? Seat of the pants or AMP meter on starter?