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IH 3500A / 674 won't move

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Sorry about cross posting this but someone in the IH construction equipment forum suggested I put the question here as well since there is more MCV knowledge in this form.  It is pretty long but I want to make sure I give all the info up front.

Last spring I bought a very used IH 3500A backhoe/loader to pull stumps at my property.  From what I can gather it is the same frame as a 674 and also the same transmission as a 574 and a number of other IH tractors.  I am having an issue where I can not get the machine to move forward or reverse other than a slight rocking.  All the other functions on the machine work great (hydraulics, motor, steering, etc).  It just has no power and won't move.  The machine has what the service manual calls a range transmission.  There are two levers next to the seat (high/low and gear selection) and a forward or reverse lever on the steering column. 

When I bought the machine I thought it just needed a clutch.  After pulling and replacing the clutch it didn't make any difference.  I then found out about it having a secondary forward/reverser hydraulic clutch inside the transmission and started looking there.  There is a pressure test port on the bottom plate of the transmission that checks the pressure the forward/reverser pump is putting out.  I put a gage on there and am getting a reading bouncing between 0 and 50 PSI.  Normal should be in the upper 200's.  I drained the system and pulled the pump.  Opening up the pump it looked clean with no scoring and very little wear on the teeth.  I replaced all the gaskets and O-rings, and made sure the pressure relief valve was functioning correctly.  After putting it all back together it made no difference.  I then bought a new pressure relief valve spring and also tried some shims and still was getting only between 0 and 50 psi.

This past week I had a bit of a breakthrough.  Originally I was thinking it was a bad forward/reverser pump ($600 part) but started thinking that maybe the pump wasn't getting enough hydraulic fluid to actually work.  I traced the line from the pump coming out of the top of the transmission over the top right side of the MCV.  I pulled the line off, started the tractor and barely a trickle was coming out of the MCV fitting.  I could put my finger lightly on it and it would completely stop.  I hooked it back up and pulled the pressure test port again at the bottom of the transmission and the fluid that was coming out was very frothy like a little oil was being mixed with a lot of air.

At this point I think the MCV is where my problem is and need some help.  I don't completely understand how the MCV works.  From reading online I think that it provides power to the forward reverser pump, power steering, and loader.  Both the power steering and the loader work great..  I see a lot online about the IPTO (I don't have one on this machine) the power steering and the loader but very little about the line that goes to the forward/reverser pump.  Is there a spring loaded diverter that is supposed to shift power to that port or does it only divert between the loader and the power steering?  I'm not sure what to check.  Should I just pull the whole assembly off and start pulling it apart looking for broken or stuck pieces?  I'm reluctant to do that since the power steering and loader work so good right now.  Is there a diagram online that shows how the MCV works?  Are rebuild kits available or do I have to order each o-ring and gasket separately?  Any other way to test it?

Thanks,

Keith

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First thing you need is a service manual for the 3500A, that manual will give you the pressures required for normal operation of the FORWARD/REVERSE hydraulic assembly and how to troubleshoot it.

I would not remove the MCV or anything thing else unless the troubleshooting guide indicates it is an issue based on test parameters.

The MCV is a whipping post for many issues that end up being something else.

We have run a 464 tractor for the past 8 years, MCV has never been an issue.

Good luck with your project.

I just went to my service manual for our 464 that also covers 385 to 784. It is a JENSALES manual and is a copy of the IH manuals.

It 9 has a section on the Hydrostatic Transmission, the Torque Amplifier and the Hydraulic Reverser.

Our 464 has none of of these so I never paid any attention to them.

Glad I don't have any of them because they are C O M P L I C A T E D!

 

 

 

 

 

 

 

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I have the service manual, operators manual, and parts manual.  It says to check the forward/reverser pump pressure by using the port on the plate on the bottom of the transmission.  I did that and was getting 0 to 50 PSI.  Normal is supposed to be 250 to 270.  It said to add up to 4 shims to the pressure relief spring to boost the pressure and that if more than 4 are needed to replace the pump or look for a leak.  I added shims with no change at all.  I was getting set to replace the pump until I found that the line that feeds the pump coming off the MCV wasn't supplying any oil to it.  The forward/reverser pump obviously won't provide any oil pressure if it doesn't have any oil to pump.  The service manual is not very specific on the MCV other than how to remove and install it.  It does not provide any troubleshooting  or explanation as to how it actually works. 

Keith

 

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Kmacht

     You do not mention anything about the hydraulic filter condition.   I would look at the filter first.  If you have frothy oil I would say it is getting air somewhere.  Have you tried over filling the reservoir by several gallons?   When you pull the filter check to see if the screen on the end of the filter has any debris on it.  This is a filter bypass valve that opens if the filter becomes plugged.   Cut the filter open and see what is in between the pleats, this may tell what if any failures you have.

GT&T

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Thanks for the suggestion.  I'll check the filter but it was replaced right after I bought it (wasnt moving then either)  All the other hydraulics  (steering, loader, backhoe) all work smoothly.  There just isn't any oil coming out of the mcv and getting to the forward reverser pump.

Keith

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3 hours ago, oleman said:

How is is your 3500A project coming?

 

It has been dark by the time I got home each night and then we got snow all weekend so I haven't been able to do anything but pull filters.  The filters were clean or at least not dirty enough to impede flow.

At this point I'm sure that it isn't moving because the mcv isn't pushing any oil out of the port that feeds the forward reverser pump.  I just need to figure out why.  The next step is probably to pull the mcv and see if anything is stuck or blocked.  

 

Keith

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NO! Do not pull the MCV yet. The oil flow from the MCV is as follows First the main 15 GPM (nominal) pushes all flow against the Flow divider in the bottom of the MCV and anything over the 2.5 to 3.0 GPM is directed out the big line at the back lower side and sent on to the loader and backhoe etcc. 

Now it gets interesting. That 2.5 to  3.0 GPM that made it thru the priority flow divider is directed out the fitting an the face of the MCV and out to steering and the return from steering is directed to the front right side top corner of the speed transmission where it is directed to a down tube that (depending on ser. number) feeds the return flow into a small hydraulic pump Early prod. or a Valve block (latr prod.) and either one of them direct the flow to the orward and reverse clutch       but the clutch is a sealed  (so to speak ) unit that when a pack is full the same volume of oil is left over and spills into a return pipe that comes back out the top of the trans. and is then sent back to the MCV where it is directed  to the PTO portion of PTO control but in your case the uunit is not equipped with PYO so it is exprange trans to provide lube to speed trans main shaft and into the rear diosed to a oil Cooler relief valve  and then out the fitting at the top left side of the MCV where it is sent out to the front of the tractor to the oil cooler and after leaving the cooler is directed back to the  differential for lube with a small diversion on it's route to feed the keep fill function for the brakes.

SO! You have a very busy 2.5 to 3.0 GPM And the trouble spot on it's trip is I suspect the forward and reverse clutch which will require a service manual.

Two Questions? On the plate on the bottom of the speed trans. is there a gear pump or a valve block.

Two- Where are you located?

PS: It would be hardd for me to believe that there are very many 3400 / 3500 tractors arround that have never had a failure in this area.

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22 minutes ago, oldihdsl said:

SO! You have a very busy 2.5 to 3.0 GPM And the trouble spot on it's trip is I suspect the forward and reverse clutch which will require a service manual.

Two Questions? On the plate on the bottom of the speed trans. is there a gear pump or a valve block.

Two- Where are you located?

PS: It would be hardd for me to believe that there are very many 3400 / 3500 tractors arround that have never had a failure in this area.

I think my system is a little different than you described above.  The return line from the power steering does not go to the forward/reverser pump down tube.  There is a line that goes from the upper left corner of the MCV to a 90 degree fitting on the top right hand corner of the transmission.  That fitting has a down tube that goes directly into the plate on the bottom of the transmission.  The passages in that plate feed the forward reverser pump.  The output of that pump goes up another tube inside the transmission and feeds the forward/reverser hydraulic clutch.  The issue is that the line coming off the MCV that goes to that forward right side of the transmission is putting out very little oil with almost no pressure.  If I get home early enough tonight I will try to get out there and take some pictures.

To answer the other questions:  On the bottom of the speed transmission there is a plate about an inch thick with 10 bolts.  If I remove that plate there is the gear pump that feeds the forward/reverser hydraulic clutch.

Location - I am in Connecticut. 

 

Keith

 

 

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Keith, If you care to send me a PM with a phone number and best time I will call you and we can discuss your problem.

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I took a few pictures last night.  Hopefully the post works.  It shows the tube coming out of the mcv that goes directly to to forward reverser pump.  This tube is pushing out very little oil with no pressure.

Oldihdsl - I'll send you a pm. 

Keith

 

MCV.jpg

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I did some more research based on Oldihsl's post.  He is right in that the forward/reverser pump gets its pressure from the return line of the steering.  What was confusing me is that I didn't realize the line went back to the MCV first, through some internal routing and then out to the pump.  I found a diagram of the MCV internal hydraulic routing (below).  Since I'm not getting any flow out of the top left fitting of the MCV it looks like either the steering relief valve or the oil cooler bypass may be stuck.  That is if I am looking a the diagram right.  Someone please chime in if I am not.  I have great power steering so I know the flow divider is putting pressure out to the steering "hand pump".  It is what happens to that flow once it returns is where I think I need to keep investigating.  Unless someone has a better idea I plan on pulling both the steering relief valve and the oil cooler bypass valve this weekend to make sure they are free and working.

Keith

 

MCV Hydraulic Routing.jpg

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Did you ever get your tractor moving? A followup may help someone else down the road.

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Not yet.  I found the power steering and oil cooler relief valves stuck in the mcv the other weekend.  When I pulled the caps and springs holding them in they wouldn't even come out when I ran the tractor with the hydraulic pressure behind them.  Since the forward reverser pump is fed by the oil bypass valve which is fed by the power steering return I am pretty sure this is part of the problem.

I pulled the mcv assembly off the tractor but have not yet had a chance to try and free up valves yet.  Things are slow going in the winter with the cold outside weather and getting dark early.  I only have the weekends to work on it.   I will certainly follow up in this thread if and when I get it moving again. 

 

Keith

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DSCF1615_zpslmmaybn0.jpg

 

You are correct on the oil flow , as a few guys have said, and I'd take a look at the oil flow coming out of the mcv to the f/r pump feed , remember this feed also goes to the oil cooler in front of the rad , does this get warm with oil flow , even a basic test of putting jug under one of hoses and removing it and run the engine a few mins.

But I have a gut feeling you are still in the wrong area , it will be in the f/r section . As said you have checked pressure at the plug , and 200psi+ is needed is not there, you checked the relief valve.

When you pulled off the bottom plate off and looked at the pump did you split the lower cover , once the cover and pump are on the bench , remove the pump and you will see theres a 1/4" steel plate sandwich between the pump and the lower cast plate. In between the two is a maize style gasket , this gasket can blow out internal and you will get little pressure out of the pump or to the valve.

Once you can get correct pressure on the test port we can then see what happens, BUT REMEMBER THE F/R TRANS NEEDS OIL PRESS TO DRIVE BOTH DIRECTIONS, A T/A TRANS ONLY NEEDS OIL IN HIGH when you have oil pressure faults.

I have seen the f/r packs in all sorts of mess, you have 2 pistons connected together and extra slip rings to ware , it may be you have a major internal leak and cannot build up any pressure in either direction Have you check the control rod and spool are moving correct . 

We sold a batch of true IH 785 fwa tractors with f/r trans and also worked on the smaller 248 often with the f/r trans , not been in one a while , but removal of the unit is like a t/a but for the small countershaft you have to remove .

I do have the factory manual I can dig out if needed.

 

Alex.

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Alex,

Thanks for the diagram.  I have a similar one but it is in black and white.  I already did most of what you suggested.  I put a pressure gage on the forward / reverser pump test port and got very little reading.  It bounced around between 0 and 50 psi at best.  I then pulled the plate and pump off.  Not finding anything physically wrong with the pump I split the plate apart.  The gasket looked good with no blown out areas but I replaced it with a new one anyways.  I also replaced the pressure relief spring and tested it with air pressure.  Putting that all back together and bolting it back onto the tractor gave me the same results (little to no pressure). 

 

I then started following the oil flow backwards from the pump and removed the line that leads from the MCV to the forward/reverser pump.  There was very little flow coming out of the port on the MCV and so little pressure I could stop it by just placing my finger on the fitting.  That is when I started investigating the MCV.  Last weekend I pulled the oil bypass spring out and found that the plunger inside was stuck, This is the plunger that is supposed to open up and feed the forward/reverser pump.  I think this is where the problem ultimately is located.  Since the forward/reverser pump isn't getting oil it can't build pressure.  It is just pumping air.  It may be that once I get oil to the pump that I have other leaks inside the forward/reverser clutch but I won't know that until I get there.  Hopefully I will get the MCV disassembled this weekend and order the parts I need to get it back in working order.  As I said earlier, I will keep this topic up to date with what I find to be the solution.

 

Keith

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Pulled the MCV pump off last night and split the plate and pump off of it.  No smoking gun but did find a few anomalies.  The flow divider valve was tough to get out.  It had movement but only about half way up the bore.  After that it would bind.  Not sure how far the spring normally allows it to move but I'll be cleaning it and the bore up with some 1000 grit sandpaper to get it all moving again.  The check valve for the power steering return was also stuck inward.  It is a little plastic two piece unit with a small spring inside.  I cleaned and freed that up as well and it seems to be working normally now.  I still haven't gotten the oil overflow valve freed up yet.  It is stuck pretty good.  It does not appear to be the source of the problem though.  After seeing how the internals work that valve only opens up if the pressure to the forward/reverser pump port gets too high.  It dumps any over pressurized oil back into the filter/bowl on the MCV.  I wasn't able to tell if there were any leaks between the MCV block and the plate.  When I split the plate off the MCV the gasket came off in pieces.  Some stuck to one side, some stuck to the other and some just came completely loose.  I removed the pump but did not disassemble it.  Looking at the gear teeth through the output port of the pump they all seem to be in decent shape.  No broken teeth and no evidence of wear marks.  The pump turns by hand with some resistance which I would expect to be normal for a tight tolerance pump. 

Next up is to free the flow divider valve and oil cooler relief valve up and put it all back together.  I ordered new gaskets and O-rings from Messicks this morning and should have them early next week.  From there I will re-assemble it all, start the tractor and see what is what.  If this doesn't fix the problem I think the next thing to look at is what type of flow and pressure I have going to and coming back from the power steering lines off the of the MCV.  I may also try tying the power steering return line directly to the forward/reverser pump feed line to see if I can at least make pressure at the forward/reverser pump.  Without a IPTO on this tractor this isn't really a need to feed the power steering return back to the MCV that I can see. 

 

Keith

 

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I have no idea if this is of any help but I managed to aquire a copy of an IH training manual for worldwide series and 84 series tractors. If I van load them in the correct order

 

20170127_214017_zpswur0as41.jpg
20170127_214300_zps6kztqqoy.jpg
20170127_214308_zpsoqnhro4c.jpg
20170127_214027_zpsethehqhl.jpg

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Sorry for the poor quality I have taken photographs of the pages. I will have to get the pages scanned.

But in the meantime

 

2017-01-27%2021.48.52_zpse4uiribq.jpg
2017-01-27%2021.48.30_zpssvq0wpgj.jpg
2017-01-27%2021.48.00_zpsdqyg0f9u.jpg

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PID

  •       Thank you for posting this service manual.   I have worked at an IH dealership and have never seen this manual.  It has information that I haven't seen in our ( US version ) of the manual.  What does the cover of the manual look like?  I'd like to get a copy if I ever see one available. 

GT&T

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Will take a picture tomorrow.

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It moves!!!!  We finally got warm enough weather here in connecticut to reassemble the mcv and get it installed.  I freed up all the valves inside the mcv, replaced the pump o rings and put a new gasket on underneath the mcv plate.  Not sure which one fixed it but the machine drives great now.  Plenty of power to go up and down hills and to do some digging and leveling with the loader bucket.  The only down side now is that the breaks are close to non existant.  I have to look up to see how they work.  Not a big deal as long as I plan for it when driving around.  Thanks everyone that contributed to the thread here and offline.  Very glad to have my machine back working again

 

Keith

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Keith, I'm in the Hudson Valley of NY and having a terrible time of it.  One of the posters on tractorbynet sent me this string which I previously had not seen.  I am a backhoe rookie but reasonably mechanical.  Backhoe goes in reverse in both forward and reverse.  This condition started two hours run time after I lost a hose.  I may have run it some with low fluid because, among other things, I am an idiot.  It's definitely full now...  Any insight you may have is appreciated.  I also have no light after work and only have weekends...

 

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Not sure on the reverse in two directions. Sounds like maybe a stuck forward/reverser clutch or the linkage in the forward/reverse lever came disconnected. Do you have copies of the service and parts manuals?  If not, let me know. 

 

Keith

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