Destroker screw on 3020 -- installation and function

[BobinSD]

I tried to install one of these today. It came without directions. Looking just behind my gas tank, I had two bolt heads exposed on the top of the pump. One bigger one along the centerline of the tractor, and a smaller (11/16ths head) outboard (to the left) of that one. The valve looked to be about the size of the smaller one, and the book (owners manual) picture seemed to imply it was outboard. I cleaned the area really well and put the destroker in place of the 11/16th bolt). When I turned it in, it was kind of hard to turn (by hand, using the little lever/T-head). The directions (in the owners manual) said to turn it in until resistance is felt, then about a turn further. I turned it in until it bottomed out.

The good news is I got the tractor started (about 15 F above, with the tank heater on for about 2 hours prior). The bad news is that backing the destroke screw all the way out never gave me my hydraulics back. I let the tractor warm up, shut it down, and removed the destroker. Re-started and had hydraulics immediately. The destroker was very polished around the outside of the pin/plunger part. Not sure if any metal was ground away or not, but it was worn for sure.

What did I do wrong? Did I install it in the wrong place? Is the plunger too long to let the pump do whatever it does when I pull it all the way out?

Also, I ran the tractor around for about half an hour and never got the temp gauge to budge off of cold. I was running the snowblower, but didn't really have much snow, so it wasn't really loaded. I normally cover almost all of the radiator on my other tractors in cold weather. I assume that's OK on these also (never had one with the vents on the side before...) This one definitely likes the choke more than the others.

Thanks,

Bob

 

[44 Diesel Tech]

What was the part # of the destroker?

 

[buickanddeere]

I had that happen with the destroker I tried to install in the 4050. The stem was too long and forced the pump into destroke even when backed completely out.
Grind the stem shorter until it just clears when backed off.

 

[JDemaris]

The destroker - when you turn it in, physically pushes down on the stroke-control valve-spool inside the pump. It will be directly in-line with the pressure adjusting screw on the other end of the pump. When you turn it back out, it should be touching nothing inside the pump if it's working correctly. Pretty easy to check. When the T handle is backed out (all the way counter-clockwise), you should be able to screw the assembly into the pump easily by hand and feel no pressure against anything.

AR33249 Manual destroker assembly for 2.4 c.i. USA built Deere pump - 39 CM3 (2.4 IN.3)

AR96625 Manual destroker assembly for 2.4 c.i. Deere metric pump (with serial # tag)

AR38225 Manual destroker assembly for German 1.38 c.i. pump

 

[BobinSD]

They gave me AR96625. I just told them it was a "pre 123000 3020" and they ordered it in. They didn't ask any specifics about the pumps.

The stem sticks out a good 1/2 inch past the taper part, so even when backed all the way out it's probably 3/4 of an inch lower than the bottom of the old bolt would have been. The way it is worn, I'm wondering if it's too big around in addition to being too long. It now has a step around the circumference, I'm not sure if it was there before, but it's definitely shinier around the edges since being installed. Hopefully there aren't metal filings swimming around in my hydraulic fluid.

 

[BobinSD]

Would it be safe to assume that this (1967, serial number just before 100,000) tractor came w/ the USA built pump initially? Could all three of these be easily swapped into this tractor, or do I probably have the USA built pump?

Any easy way for a novice to figure it out? Obvious external differences, or pictures on the web?

I'm guessing I picked up the wrong part,

Thanks,

 

[Tx Jim]

JDemaris's post is correct the part # listed for the 3020 in part cat 858 for SN<123000 AR33249 SCREW 1 (MANUAL DESTROKE)
with hyd pump with "no serial number plate"

And AR96625 is for a installation in a replacement hyd pump with a serial number tag

 

[JDemaris]

3020 had a USA pump originally. If it got replaced, it will be metric. If it was replaced with a metric pump, the pump will have a metal serial # tag on top of it. Original USA pumps have no tag.

The replacement pumps with tags are all metric threads also (as I recall). So, the pump destroker should also have metric threads. If your destroker screwed in OK without forcing it, it should be the correct one.

AR33249 is the manual destroker for the original non-metric pump (with no tag plate).

AR99625 is the metric destroker with a T-handle on top, and RE13271 is the metric destroker with a hex-head on top.

 

[JDemaris]

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[BobinSD]

Thanks JDemaris and TXJim,

In your parts diagram, is the front of the tractor to the right?

Would the metal serial number plate be visible from the place I'm accessing these plugs (under the air cleaner, behind the gas tank), or would it be under the sheet metal? I'm not seeing a tag, but the part I got threaded right in. I'll measure the threads on that and see if they are metric or not (I got the part that fits the metric pump).

Thanks,

Bob

 

[JDemaris]

Serial tag is near the top as in the diagram.

I told you something that is incorrect. The metric replacement pumps are not 100% metric. They have an odd mix of SAE and metric, like when the Ford Pintos first came out. At least Ford used to color code them (blue for metric).

The threaded hole where the destroker goes is not metric on either pump. Both destrokers use threads that are 9/16" by 18 threads per inch.
So the wrong destroker would screw in easy -= until it hit the valve inside the pump and opened it.


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[BobinSD]

thanks for clearing that up. I figured it was 9/16ths, but obviously not 12 tpi.

I'm guessing I need the other part. I'll look underneath for the tag, but I seem to recall the assembly threading in easily for a couple of turns, then needing the wrench (but still smooth, not cross-threaded) to seat it all the way. At less than $15 I'll probably just order in the other one and hope it's got a shorter (and maybe narrower) stem -- assuming of course that there's no ID tag.

Thanks for the help, I'll post back and let you all know how it worked out.

Thanks again,

Bob

 

[Bob in SD]

The dealer actually had two of these in stock. This one had a shorter stem, and worked fine. Threaded in w/ no resistance, and I could spin the stem T-handle in w/ my pinky for a couple turns before it contacted.

I had previously used the tractor to move some snow today, and didn't re-start using the destroker, but I'm sure it'll work as advertised.

Thanks for all the help,

Bob

 

[Bob in SD]

Just to document it for the next guy, here is a picture I took of the two screws before installing the correct one. The 33249, for the non-metric, original equipment pump, is on the left. The 96625, which should fit the metric replacement pump, is on the right.

The threads are the same, so the wrong part will screw in. I didn't think to mic, or even compare the stem thickness.

Thanks again for all the help,

Bob