Transmission issues

Beowulf

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My gear drive unit won't move most of the time unless I put it in the highest gear. Does this sound like a belt issue or transaxle? What should I check? it is very hard to access anything on this machine I haven't really looked at much.
 

bertsmobile1

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The clacker valve is on the wrong side of the thimmagig.
This has ofened the mower gods so you will need to get naked at mignight on the first full moon push the mower into the middle of the lawn pointing exactly north then dance around it chanting.
"If they don't know what mower I have they can not help me fix " 100 times in esparanto.

After that look under the seat and post the mower details from the tag plus the make & model number of the engine.
 

Beowulf

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Sorry, entered that in profile but doesn't seem to show.*

136M660G062 built in the 90s
Briggs motor, I think 31xxxxx series
 

shiftsuper175607

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Sorry, entered that in profile but doesn't seem to show.*

136M660G062 built in the 90s
Briggs motor, I think 31xxxxx series

We had a detailed thread not long back about a similar sounding problem.
It was wear in the deck and linkage etc...whereas only at highest speed setting would belt be tight enough to move mower.
 

Beowulf

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We had a detailed thread not long back about a similar sounding problem.
It was wear in the deck and linkage etc...whereas only at highest speed setting would belt be tight enough to move mower.

Thank you. Do you recall if that was here in the MTD forum?
 

bertsmobile1

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May have been in the transmission section.
Boo will most likely chime in cause he is good at searching this stuff out, I am hopeless at it.
Now check this site out and double check this is what you have . It helps a lot if we are all talking about the same mower and if we all use the same diagram then we can refer to parts by numbers so we are all talking about the same part.
https://www.partstree.com/parts/mtd/mowers-lawn-garden-tractor/43995-136m660g062-mtd-lawn-tractor-1996-lowes/drive-frame-lower-pedal-assembly-wheels-rear/
It takes a few minutes to get your head around how the system works but once you do it all becomes blinding obvious.
SO pulley 74 puts a fixed amount of tension on belt 79 ( the top one ) by means of spring 66.
Pulley 82 has a fixed top & bottom, but the middle can slide up & down.
As this happens it changes where the belt runs, closer to middle or right out to the edge.
Because it is really two pulleys the net effect is the came as a drill or lathe with a pair of stepped pulleys.

When you put your foot on the go pedal you change the tension on the belt 25 and if the amount of tension you apply is greater than the spring ( 66 ) it forces the sliding plate up which makes the diameter of the drive pulley smaller so it turns faster and you go faster.

So first off you need to look at the spring and all of the pulleys.
The spring must be there and have not cut a hole through the mountings.
The pulleys must all spin freely & quietly .
next check the two belts fr wear and faults like cracks & burns.
The belts are the same width but the rear wears faster than the front cause it is shorter,
Unfortunately they must be replaced as a pair, which is a bit wasteful but that is how life goes.

Also important is the pivot point for the speed pedal 84, note it has 2 bushes, part 28 these wear preventing the pedal applying full tension so they should be replaced .
The same for bush 70 and check the hole in the tensioning arm it goes in. Same thing, floggs out oval over time. It is supposed to be lubricated monthly but no one ever does it.

If the belts need replacing they must be genuine or certified OEM replacements as they are not standard A or B section belts. I use Stens exact replacement belts down here because they are good quality and come for a better price.
Down here the pair of belts is over $ 200 ( Aus) .

That little lot shoud keep you out of the bar for a day or two, or drive you to drink.
The previous thread was a troybilt mower. not exactly the same as yours but the same system.
 

Beowulf

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Yes, that diagram does appear to be the proper unit.

Thank you for the excellent write-up. I certainly understand the system better now.

So now I need to find time to dig and curse and cuss and skin some knuckles.
 

bertsmobile1

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And get some tall stands so the mower is up high and STABLE.
Some find it easier to tip the mower on it's side.
I usually remove the seat all together ( check the wires on the seat switch, photo & mark them.

And yes take photos of everything.
MTD use the same chassis pressing for around 200 different models so there are holes everywhere under there.
The suggestion is to take a before & after shot as each part get removed.
We get lots of "where does this spring attach to" questions.

If you want to search more the magic word is Varidrive _Variable Speed Transmission. that should bring up a lot of posts on here at least.

A few good videos out there, Tary & Donny boy if you want to see them being fixed ( mostly belt replacements )

If you can get it up high & stable enough ( deck removed of course ) get SWMBO to start it & work the tranny while you lay underneath so you get a good feel for how it all goes together before you start shedding blood.
 
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