Bench test an 8 speed?

[WH 312-8 Fan 9]

I'm getting a 3x0-8 parts tractor from a buddy of mine. I plan on selling off the sheet metal and my buddy is keeping the motor.
My intention is to use the rear end as a fathers day present for my dad to replace the Uni-Drive he has in his 1986 312-8 with 1,800 hours on it.
His transmission is fine but it is having issues with the keyed axle and the hub assembly on his.
He is in Western PA and I am 5 hours East In Lancaster County, PA so I can't just hop over.
The pars tractor isn't a runner and my buddy bought it only for the mule drive so he has no idea if the rear end is good or not.
I don't want to waste a trip and labor to install a potentially bad transmission.
now, I'm assuming it would be involved to tear out my dads transmission and crack it open and replace part as needed. I believe a whole swap out would be quicker and easier on both our schedules.

How do you bench test them? Is there a way with out hooking up a motor to it and running through the gears? I will most likely have it with me when I go to the Wheel Horse show in Arendsville, PA next month (along with rest of the carcass)

Thanks in advance.

[doc724 924]

In my experience, the transmissions themselves are rarely the problem.  Unless someone stripped the gears due to abuse, they are pretty robust.  What is a problem is seal failure-often caused by failure of the needle bearings that are behind them.  If one of the needle bearings fails, you have to crack the case to replace it.  If one of the main axle needle bearings grossly fails, the loose needles can trash other things inside (like the main differential carrier bearing which is NLA if you have an older transaxle).  So, with that in mind, check all 4 of the shafts that exit the transaxle (input, brake and output).  There should be NO up/down or left right movement.  Output shafts can move in/out by 1/8 inch. 

Another thing to look for is water in the transaxle.  Drain it and see what is inside.  Pour a couple of quarts of diesel fuel in there and swish it around for 15-20 minutes by turning BOTH rear hubs at the same time.  Run it through the gears as well (it will be difficult to turn by hand).  The gears will be a bit noisy with the diesel fuel in there. Then drain it.

I have had good success using the above diagnostic procedures.  I am sure there are many RS members who are more experienced that can offer other solutions.

[WH 312-8 Fan 9]

Thanks for the reply. I'll start there. If worse comes to worse, I can take it to work and tear into it. I agree, they are definitely a robust transmission. 
. I will probably mount the wheels onto the hubs so it's easier to work the transmission.
I'll post what I find out. Thanks!

[stevasaurus 22,273]

Actually, just turning the wheels is not going to tell you to much.  Put the rear end on blocks.  With the trans in neutral spin one of the tires, the other should go in the opposite direction.  You can also keep one of the tires from turning (by holding it) and turn the other tire in either direction.  Do this on both sides...this tells you that your differential is OK.

Now take off the belt guard and belt.  You want to put it in each gear plus the hi/low (8 speeds) and turn the input pulley in a counter-clockwise direction.  You can tell by the feel if every thing is OK.  Everything should turn freely just be doing it by hand.  This will tell you if anything in the drive train is suspect.  Trying to turn the tires while it is in gear is much like trying to start and old 3 speed car by jumping the clutch...the best way is by turning the input shaft by hand...or by using a long fan belt and another tractor and/or an electric motor.  If it has a dip stick, see what the oil looks like...if everything else turned freely and felt OK, I would not worry about any milky oil at this point.  If no dip stick, stick a rod down through on of the top holes in the trans...usually where the seat and fenders bolt on. 

[WH 312-8 Fan 9]

great information! 

Actually, just turning the wheels is not going to tell you to much.  Put the rear end on blocks.  With the trans in neutral spin one of the tires, the other should go in the opposite direction.  You can also keep one of the tires from turning (by holding it) and turn the other tire in either direction.  Do this on both sides...this tells you that your differential is OK.

Now take off the belt guard and belt.  You want to put it in each gear plus the hi/low (8 speeds) and turn the input pulley in a counter-clockwise direction.  You can tell by the feel if every thing is OK.  Everything should turn freely just be doing it by hand.  This will tell you if anything in the drive train is suspect.  Trying to turn the tires while it is in gear is much like trying to start and old 3 speed car by jumping the clutch...the best way is by turning the input shaft by hand...or by using a long fan belt and another tractor and/or an electric motor.  If it has a dip stick, see what the oil looks like...if everything else turned freely and felt OK, I would not worry about any milky oil at this point.  If no dip stick, stick a rod down through on of the top holes in the trans...usually where the seat and fenders bolt on. 

​I will try this as well. I'll leave the rear end in the frame and use the belt to turn. I don't have any spare electric motors but at work I might be able to figure something out.
I'm glad I'm not trading much for this tractor. I don't want to have to split it open and put new bearings or seals in, but now is the time to do it before it gets installed. I know my dad won't be in the mood to do it. He doesn't like to slow down to tear into his 312-8. It's a year round tractor so it never sits much.
 

[stevasaurus 22,273]

You need to take the belt off to turn by hand...off of the engine pulley.  Believe me, you will be able to tell if something does not feel right just by turning the input pulley by hand.  You do not have to have it up to speed.    Let me know...seriously, I think by hand is better...you can feel it.    Yes, if you are going to flush it with diesel, you are going to want to get it up to speed, but I would not do that until I turned everything by hand.  If it turns by hand (counter clock-wise) and feels good...you should not cause any damage by running it with diesel to clean it out.  Make since??

 

Edited May 19, 2015 by stevasaurus

[WH 312-8 Fan 9]

that makes perfect sense. I'm sure i'll feel some sort of "hitch" or "click" in the gear sets through the input pulley?

[sorekiwi 761]

There is really no reason to run the transmission with an electric motor, these transmissions are non-syncromesh so they shouldnt really be shifted "on the fly".

As Steve has said, turning it over by hand should enable you to feel any problems.  

One problem that might not show up is worn dogs on top gear, this causes the trans to jump out of top gear when the transmission gets unloaded.  This is hard to simulate, either by hand or by powering the transmission with a motor of some description.

[stevasaurus 22,273]

Mike...the idea of bench testing the trans is to use an electric motor to turn the input shaft while running in each gear.......not to shift while running.  I use this method in transmissions where I have already figured the trans to be OK and just wanted to run diesel to clean out...or to test a trans that I have rebuilt to make sure it runs OK before I take the time to put it back in the horse..  Check for leaks and level of oil.    I have a 1/3 hsp motor that I strap to the bench and plug in so the input shaft goes in a counter clockwise direction.  The speed of the motor seems to be pretty close to the speed the trans would run if it was running off the engine on the horse.

Mike is right...if there is a problem with a trans that jumps out of 3rd gear with a load (a worn 2nd/3rd fork gear) you will not know with out running the horse like with a snow blade in 6" of snow in 3rd gear and it pops out of gear.  To me...if you test the trans the way I said...and it feels OK...I would take it home.  Plow snow in 2nd gear.  My point is...if it all feels good...the trans is worth taking home.  You may have a bad bearing, a leaky seal and maybe a worn 2nd/3rd fork gear, but you have a good trans that is good and definitely fixable for not much $.  Just so you know...I would almost take any trans home.  I cleaned one up that was just crusted with rust.  A lot of penetrating oil, a lot of electrolysis, some wire brushing, new bearings and seals...it went from junk, to a parts trans, to a fully functional trans.  It was a labor of love and I was able to bring it back.  I have not opened one yet that was not fixable...that is important to know.  I would not pay more then scrap price for one that did not turn though...but it would come home with me.  Hope that helps. 

Just so you know...Sorekiwi is excellent with transmissions also.    Actually, he is better then I am at it..
 

Edited May 20, 2015 by stevasaurus

[sorekiwi 761]

Steve, its been 3 or 4 years since I've been inside one, I'll need to watch one of your video's before I get into the next one!

[WH 312-8 Fan 9]

It's you guys that make forums like this so great.

I appreciate both of you guys for throwing some perspective and experience my way. I did run over and help my buddy take the motor out. He's keeping it. I'm getting the rolling chassis.
I put it in each gear and then rolled the tractor across the asphalt listening for clicking and checking for any hesitance. The fluid looked good. I'll still drain it and fill with new. once I get the sheet metal off and drop the uni-drive. I will still go through yet and run the pulley by hand and visually check the seals. I'll probably also put a new shift boot on the gear lever. And I suppose paint wouldn't hurt either.... the list seems to grow!

Thanks again guys.