1973 auto 18 hydrostatic tranny lacks power

[wheelhorse-c-161-1979 117]

I've had my 1973 auto 18 for about a month now. Every week I've been improving things on it to make it more functional. New hydraulic lines on the auto loader, changing the spindles, etc..    Every day I have it I wonder how I ever lived with out it!!!!

 

The one thing I'm starting to get concerned about is the tranny.  The tractor moves forward and backwards  but lacks power. Also when in it starts in motion the tranny makes that whirring sound that reminds me of a car  with a power steering pump low on power steering fluid when you would turn the steering wheel.  The whirring sound is always present in reverse and when moving forward at slow speed.

 

The tranny fluid F seems clean and up to where it should be on the dipstick.  But the tractor has a tough time going up a hill in reverse, or pushing the front end loader forward to scoop up a load of dirt or what ever.   In forward it seems to go relatively fast when the tranny is first engaged.

I downloaded the Sunstrand Hydro manual at http://www.wheelhorseforum.com/files/download/24-sundstrand-hydro-transmission-repair-manual-492-4206pdf/ 

 

I found the transmission oil filter which looks like it hasn't been changed in a while. But I'm afraid to remove it if I can't find a replacement. Also I'd change the tranny oil but can't figure out exactly from the manual  where the transmission drain plug is.  I think it might be on the transaxle but the manual doesn't point out where.

 

If anyone has experience with this tranny I'd love some suggestions.

 

 

Any ideas?  Is this an adjustment or am I headed for a tranny rebuild?

 

Thanks for your thoughts and help

 

Jack

Edited April 28, 2014 by wheelhorse-c-161-1979

[daveoman1966 3,628]

To drian the fluids, you'll find a hex-plug on the bottom of the gearbox.  It is probably packed full of dirt/mud after near 40 years or so and may be a little tight.  You can still buy a new oil filter # 79-5270 from dealers....about 15 bux.  If the fluid is pinkish...that is ATF and thats what you should refil with.  You can, however, change to 30w motor oil, but you MUST completely drain EVERYTHING to do that. 

 

In any case, the symptoms you've given are typical of a worn out or damaged hydraulic pump and / or hydro motor (bolted to the side of the gearbox).  No amount of fresh oil or number of filter changes will restore the worn out parts.  You MAY gain a little, but in the end, you will need to have the pump AND motor sections overhauled / rebuilt.  Yours is a 'separated' system, meaning that the pump and motor are NOT bolted together as a unit.  There is a 4-tube manifold between these two components, as described in the manual you bought. 

[wheelhorse-c-161-1979 117]

Hi Daveoman,

Yes it's F transmission fluid. Doesn't sound too good.   

 

For now I'll start with the new filter for sure.  

 

If it comes to that, who does the rebuild of Sunstrand Hydro?  How many $$ you figure?

Thanks for pointing me  somewhere

 

Jack

[pfrederi 17,173]

I hate to say this but you probably should have looked at the mobility issues before you spent a lot on other parts. The last time i asked a hydro place they talked about $5-600 to overhaul the hydro motor...about the same for the pump.  (and that was 3-4 years ago) In all likelyhood if one is worn so will be the other. 

 

Many of us here have repaired our D series systems.  There are several threads on the topic. If your pump/motor valve plate and slippers are badly worn you cannot repair them you will have to try to find new parts (very expensive) or buy a take out pump/motor and see if it is repairable.   The job is not terribly complex but it is a lot of work to pull the pump and requires a few tools, (a press is really needed for one procedure on the hydro motor) but most importantly a good place to work.  This is not a shade tree project.  Hydro work requires cleanliness....

 

Incidentally the ATF used should be Type A (now known as Dexron)  They have a universal fluid now that covers both Dexron and Mercon.

 

Read the manual and see if you want to tackle it.

Edited April 29, 2014 by pfrederi

[wheelhorse-c-161-1979 117]

Hi Paul,

 

Thanks for heads up!
 

What I don't understand about the "auto 18" is how the automatic transmission changes power  or torque when power is needed.  Does it have a way of varying the load demand to handle heavier tasks? As I would use the low gears on my C-161? 

 

Yeah Paul, this will be probably be a big chunk, but I knew that a 41 year horse would need some care.  The tractor otherwise runs amazingly well and is rust free. So I still would (so far) rather sink a few more dollars into good American made steel work horse, than a new made in china tin can with wheels any day.

 

Last year I fixed up my 8hp '73 Gravely 408 that I had since I was a kid and use it now again as my main mower. It's built like a tank and there are no problems. It sat in the garage patiently while I kept dealing with a newer shinny flimsy Craftsman LT1100 that claims to have 18hp.  Now am selling the 2005 Craftsman as it's a big headache.

 

Back to the Wheel Horse though… and the auto 18.  I think I regret not finding an 8 speed D180 as auto transmission are just a way of making the simple into something complicated.

 

If worse came to worse, is it realistic to  swap out the auto transmission for an 8 speed manual?

 

Meanwhile here are a couple of pics of my goats who seem to like the old Wheel Horse!

 

Jack

 

 

 

 

[pfrederi 17,173]

There were never any gear driven D series.  The piston to piston hydro has a movable swash plate in the pump.  This determines how much pressurized hydro fluid will be fed to the hydro motor base on how tilted it is...the tilt is controlled by your direction control lever.

 

Whether you repair it yourself or take the pump and motor out and find a repair shop your tractor will be down for an extended period.  The hydro motor is the easiest part to remove...but you have to have a press to disassemble it if you want to look at it and possibly fix it yourself or you can take it to a hydro place and see if they will work on it.

 

Here are links to a couple threads on how you can work on them yourself

 

Edited April 29, 2014 by pfrederi