FORD 3930 Help with multiple questions

snowcrash · Feb 26, 2014

Hey everybody,

We bought a 94 3930 Diesel Ford back in September or October of last year. I felt it needed a clutch but my dad didn't think so, but we went ahead and decided to split and see. It still had some life but since we had it this far, we decided to go ahead and replace it. I guess this was the simple part but I totally Fudge up taking it apart. It's an 8x2 transmission with a spring clutch disc and a 4 lever pressure plate.

We took the old parts to a well know clutch place not far from us and got the flywheel turned, a new disc and new pressure plate(been remanufactured by them).

I forgot to undo the throttle linkage rod before trying to separate it and it seems to have really messed things up. It bent the rod, it bent the throttle assembly where the throttle rod comes from the pump and the accelerator pedal hooks to, and it bent the throttle stop(thing on top of the pump that gives it throttle where the linkage rod attaches. I'm thinking that is the throttle shaft of the pump.

We got everything bent back to where it should be or close to it, but now it just didn't want to throttle up to around 16 I guess? Could it have done something to the rod(throttle shaft) coming out of the top of the pump that controls throttle up or down such as twisting it inside the pump? The only way I could get it to throttle up was take off the cap on the high throttle set screw and adjust that rod out to allow the throttle assembly to rotate more and give it more throttle. It seems like has giving me throttle but my other question is now, what is the max throttle RPM for the 3930. Everybody's could be different but probably close. I just need to know what rpm it throttles up to at full throttle. Also, what is the correct idle or low throttle rpm with the throttle all of the way throttled down?

The tach only goes to 2500 and that thing seems like it would be screaming if it went that much. It's around 2000-2100 I think at the moment of where it will throttle up to but it seems like way more than it had before. As long as my tach is accurate, I guess that is what I am running at.

I'm assuming adjusting the high throttle screw will not hurt anything as long as the motor isn't turning to many rpms? If there is a chance that the pump rod got bent or twisted, any idea on what it might cost to fix that? It really doesn't need to be rebuilt because it runs great and no leaks but just didn't know if that part or parts could be fixed without costing a fortune if that is the case.

Is there a way to check the RPM's without the tach, I don't think there is a way but have no idea with a Diesel? I am pretty sure my tach is right but with my luck, it's not and I'll mess something else up?

With the PTO, should it stop when pressing in the clutch or is it basically engaged the hole time while it is in gear? I checked a 3910 and it didn't seem to stop so I am thinking that is normal but I just want to make sure.

The tractor also has a knocking sound either around the throwout bearing area or right kind of underneath the gear shifters. It maybe had this before and we just didn't notice it but we did notice it now. It sounds louder around the shifters than the throwout bearing but just not quite sure. If you press the clutch in, the noise gets quieter as it almost goes away. Do you guys have any ideas what might be causing this noise?

I'm really sorry for all the questions but the high and low idle speeds are the biggest thing I guess. This whole ordeal just has me so upset with myself for forgetting to remove one simple part that I knew had to be removed. Hopefully some have some ideas because I hate to split it again to find nothing wrong with the clutch.

Thanks for any help,
Charlie

Winmac · Feb 27, 2014

Personally I would try to straighten the bent arm on the fuel pump before changing any settings.
Perhaps another member with the same tractor could provide pictures of their undamaged linkages.

The noise you as you describe it may be the front bearing failing in the transmission, but must first ask if a new pilot and throw out bearings were installed, with correct free play adjustment?

snowcrash · Feb 27, 2014

Yes, we did replace the throw out bearing and pilot bearing when we replaced the clutch and has the right free play. If the front bearing is coming out, is that something very hard to replace and how do you go about doing it? Anyway to figure it where the noise is coming from?

The rod was not completely straightened out so you could still see the bends but just didn't know the exact bends. I'm going to look at one once I can get my eyes on it but the rod itself was bent some and very close in my opinion to what it was.

The mechanism the hooks to the throttle shaft on the pump was bent up. The top piece the rod goes in was unharmed but the part underneath the first piece that has the bent down piece that hits the idle stops on the throttle was bent up badly so I put that back in a vice and made it look like it should.

Before I adjusted the high idle stop on the pump, when you pulled the throttle lever, it would pull the rod all the way back to where it would hit the high idle stop and if you pushed it all the way forward, it would hit the low idle stop and basically want to die because the idle was not enough. I know that the tab I hammered back down on that is supposed to hit the idle stops might not be exactly where it was before but it doesn't make sense why I had no full throttle before.

That's why I adjusted the stops, but would like to know what the tractor rpm should idle at and the rpm should throttle up to.

Looking at videos on cav pumps, it doesn't look like it could have done a lot of damage in the pump if it did, but it maybe could have either stretched the spring that connects to the throttle shaft inside the top portion of the pump or maybe it messed up the part that the spring connects to on the throttle shaft. Unless to much tension could cause problems with the governor that the spring connects to from the throttle shaft.

In my thoughts, I'm having to turn the throttle shaft more to achieve the same amount of throttle that it would do before adjusting the stops.

Oh yeah, even if the rod is not right, before adjusting the stops on the pump, I took the rod off and turn the mechanism that is attached to the throttle shaft and when it hit the high idle stop, it would not tach up but to like 1800 rpms I think? That makes believe that there is something screwed up in the pump but I might can achieve the set rpms low and high by the screws.

Winmac · Feb 27, 2014

The arm on the fuel pump has bent or has moved on its shaft and changed position somehow. It's unlikely there is any real damage done, the lever arm only changes governor spring pressure.

I don't know the transmission well but generally you would split the tractor and partially disassemble the transmission to replace the input shaft bearing.

snowcrash · Feb 27, 2014

That is what I am thinking also about the shaft changing position. Would you just split the tractor where you would to put a clutch in or would you split it there and also behind the shifter to where it bolts to the rear-end part, or do you happen to know? Thanks

TractorTech · Feb 28, 2014

I would agree with the throttle shaft being bent. It isn't leaking fuel through the injection pump cover? It is not real expensive to fix just that shaft and is not real difficult, just tricky.
High RPM is about 2300, low is about 750-800.
The PTO is an independent style if you have a single clutch. It is 'independent' of any other action or operation of the motor or transmission. The PTO lever on the left side controls the on and off as well as feathering of the PTO engagement.
The input shaft bearing is replaced from the front end of the transmission. Split as if you are replacing the clutch. I tend to think that the noise is probably coming from the new throwout bearing, however. Either way, the split is the same place.

JohnnyArcher · Mar 1, 2014

need to replace seal pto

jimmysisson · Mar 1, 2014

Johnnyarcher, you'll get more advice if you start your own thread, and say more about what your tractor is, how long owned, symptoms, what you know already. Lots of help on here for you.
Jim

snowcrash · Mar 2, 2014

Thanks for the information on the tractor idle and rev settings. I've got it up to maybe 2100 but I don't have a whole lot of idle adjustment left on the high side, less than 1/2" of threads I would say, so I know there has to be something messed up inside the pump?

I've got some more questions now for you now.

Since it sounds like the throttle shaft is screwed/twisted up in the pump, where does one find that part to fix it or is it best to take it to a shop? If taking it to a shop, does anybody know of any really reasonable places to take one or send it to? The pump doesn't really need to be rebuilt other than replacing the gaskets in the top half I guess. At least if I can get the throttle fixed, that would be one less thing and I would feel better about myself of making the mistake.

I've seen some info on taking the top part off but searching google has not produced any results on find a throttle shaft and the ford catalog lists the part number but doesn't list a price only to say call your dealer.

Is there any good write-ups to removing and installing the pump back on the tractor? I think I found one, but thought there could be a better one so it doesn't hurt to ask. I probably should start another thread, but is there any write-ups showing how to remove and install an injector pump on a 5000 with Turbo that has 4 lines coming out of the top. It is a Simms I believe. It needs to be rebuilt so if I have to send the 3930 pump off to fix the throttle shaft, I might just send this one with it also.

We have a guy coming on the side that works for Ford tractor place during the day in the shop to take a look at it and maybe he can narrow down the knock noise. Whatever I find out on that I will report back.

Thanks for the help so far,
Charlie

TractorTech · Mar 5, 2014

I had a used shaft, but haven't had time to look. You might try a used tractor yard like Abilene Machine, Alexander Tractor or Google salvage tractors for the part.
If not, your idea about sending it in to rebuild shop with instructions on just replacing the shaft and top seals only should be doable for not a lot of money.