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Ragnar

IH 806D T/A or MCV problem

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1967 IH 806D with 8000 hrs.

PROBLEM:

Tractor SOMETIMES loses power to rear wheels and will just slowly roll forward or backward in forward or reverse, low or high. When it is working correctly clutch does not slip and tractor will pull about anything, but occasionally she just stops wanting to move. When this occurs, if the tractor is idled up and clutch pedal is pumped several times she will finally "clunk" solidly back into gear. The last occurrence was last night, I used her to push out a few small cedar trees and stumps, she pushed them out like nothing and had power enough to bring front tires off the ground with no slip when the bucket dug in (not that I recommend this), then on way home in 4H she seemed to slip and when I went to back her back in she didn't want to move. Let it sit a couple minutes idling, tried again and it worked fine.

What's been done:

1) All hy-tran and filters changed twice in last 10 hrs..(trying to get it really clean which it now is)

2) Found that if it "slips" and I remove safety check valve, put a bucket under it, briefly start tractor, let it clear air from mcv, pump seems to "re-prime". As a matter of fact this method had to be used after hy-tran fluid change to get t/a to work again. Tried steering wheel method, but it wouldn't catch prime.

What's suspected:

I suspect I may be sucking air into the mcv, but maybe I am wrong and T/A is starting to go out, when tractor is working it works smoothly. Dump valve sticking?? T/A?? MCV?? At this point I am unsure and think it may be a combination of issues. What's funny to me is how well she works in all gears low and high when she wants too.

Any input sure would be appreciated, I really like this old red tractor.

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I have the same kind of problem with my 806. When I park on a hill with the fluid running to the back of the rear end. I lose prime as well or

if it sets for a long time. Sound like it could be a pick up problem. I'll do some asking around I know a old IH mechanic. I've just been putting

up with mine because its not used a lot. Hope you get yours fixed I'd like to know what you find out.

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I alway start by reccomending that you overfill the trans by at least 5 gallons of HyTran. This covers a potential suction leak point in the trans-differential gasket area. If that does not help a reman of the MCV is in order, I have been replacing the stock MCV pump with one from a 86 series tractor. The stock MCV for a 06-66 series tractor is 9GPM The 86 series MCV is a 13GPM pump. This seems to make up for the old age internal leakage that is present in most all of these near 50 year old tractors. Good luck.

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Is the oil light flashing when it acts up? Or working at all? The oil light will flash when you lose engine oil prssure AND lube pressure on an 806 .Should be on whenever the clutch is pushed in. Other wise take the sender switch out of the MCV port and plumb in a gauge, should have 18 to 22 PSI.

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Thanks guy's. I have noticed my oil/pressure light has been flickering a lot I will see if I can rig up a gage with those size threads. I am beginning to think it is all to do with air getting in there so I will try your trick Gonzo by over filling her at least 5 gallons. Cowwboys post got me to thinking the first time this happened I was on a steep hill moving round bales. I think I better see about rebuilding the mcv and upgrading the pump like Gonzo said. If it turns out to be the T/A I am going to delete it. Sure hope I don't end up doing a split in the near future. Any recommendations on suppliers of MCV kits and pumps? Also are there any side effects to overfilling the case? I can't see how it would hurt anything.

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How's the steering when the tractor starts to act up? Stiff or does it turn easy, I'm going to work on an 856 this week that has the same problems.

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My steering quits when mine acts up.

I'm lost on how the eng. oil pressure has any thing to do with the MCV or the T/A.

gonzo 1066 thanks for the 5 gal. trick I'll try that on mine when I get home next time.

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They both turn on the same warning light. Later tractors had a seperate warning light for lube preaaure and engine oil pressure.

I have a '66 model 1206 that has the extra lube pressure light, and a '67 806 (by serial numbers) that doesn't. Kind of strange to me.

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They both turn on the same warning light. Later tractors had a seperate warning light for lube preaaure and engine oil pressure.

I did not know that.

Thanks for the help.

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I lose steering power as well when mine acts up, which is problematic loading round bales on the trailer. I usually have effortless steering so I am leaning hard towards unchecked air in my system. I'm going to keep digging til I get it figured out.

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I lose steering power as well when mine acts up, which is problematic loading round bales on the trailer. I usually have effortless steering so I am leaning hard towards unchecked air in my system. I'm going to keep digging til I get it figured out.

I also noticed that when I checked the trans oil level the last time it acted up. It was really airy looking but not foamy.

Let use know what you find out.

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Never thought of that check, I will keep an eye on it. Tomorrow I'm going to get more hy-tran and overfill it as step #1. The next step will be checking the hyd. pressure and rebuilding MCV and adding that 13 gpm pump. I want to make sure I don't get way out away from the house and break down. I appreciate all the tips you all are throwing my way. Thanks. I'll keep posting as I eliminate the possible issues. I guess there's nothing on a tractor money can't fix, wish I had some.

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I just finished repairing a 1066 that had the exact symptioms you have in the 806. I remaned the MCV valve and installed the 86 series pump,rased the hyd oil level, and now it works just fine.

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The larger pump volume willm not do anything for the steering and TA leakage since that part of rhe MCV has a priority 3 gpm flow. A larger pump will put more oil through the oil cooler which then returns to lube the range transmission and differential. It will give you more reserve as the pump wears out and the flow starts to drop off.

Adding the extra oil insures that the entire suction side of the hydraulic system will remain below the oil level so if there are any leaks the pumps will be drawing in oil rather than air. If the extra 5 gallons helps but you still have problems on hills you may have to go a bit more. The only downside other than the added expense is when it come time to change the filter some of that extra oil will now come out along with the normal amopunt that is in the filter.

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Gonzo glad to hear your 1066 is back in business. I'm adding the oil, hope that does the trick, but I am also gonna get the kit to re-build the MCV. Need to find a 86 series pump to put in there while its tore apart. Where you guy's order your parts from?

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I highly suggest hy-capacity. Do you have any local independent repair shops they might be dealers. If not PM me im in southwest iowa and can get you a pump.

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gonzo is right on. always update the mcv pumpwith the later 13-15 gal per minute also make sure oil cooler is not plugged and cooler lines are in good shape, have seen them blow with new pump.

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I'm going to get the hy-capacity and rebuild the MVC pretty soon. I added about 6 gallons overfull on the hy-tran and so far so good, haven't had a problem yet knock on wood. I will see if it continues to work good when I brush hog in the next week or so. I want to test it for a few hours to determine if it was the seal sucking air, which is highly suspect. After I am sure it was the seal, or not, I am going dig into the MCV and pump which is just a good idea, as tuff as this tractor is its probably still got the original pump and MCV springs in it and use a fresh set. I probably just order a pump and have it shipped here when I do. I want to get on some hills and ditch sides to see if it still loses prime with the overfill.

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If anybody is still following this here is the latest. Overfilled with hy-tran, fixed a short in oil/mcv light. Used tractor a lot mowing, and thought it might be ok with just added oil, but while mowing a big pasture, oil/mcv light started flickering so stopped and pushed in clutch. When I went to let out the clutch I had lost a pulling power and tractor barely crept forward. Oil/mcv light came on. Steering/brakes stayed working. Shifted t/a to low and light went out and tractor moved again. Went back into high side of t/a and oil/mcv light back on bright, tractor jerks alittle like its trying to go but won't. Finished mowing in low side with no problems and no warning light.. So Any ideas ? Leak in high side? T/a?

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It sure sounds like a failure in the high side of the TA. Using test gauges can show for sure.

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Thanks Owen. I guess I will see if I can figure out how to do that. I was thinking the high side and low side would not work if the pump was bad or failing, so It seems to me I must be leaking pressure on the high side because the low side is ok?? If it fails to meet the required pressure I guess I must have a leaking gasket in the mcv or connection. I am not an expert on torque amplifier tractors and am still learning.

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If the tractor stops moving while still in gear the fix will involve a TA,

Will explain when I have more time to type.

ed

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