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Hydrostatic transmission-Suddenly forward is weak

#1

L

larryuno

Hi, the mowing day started normally. After about half acre one of my (rear) tire chains slipped free and caught in the mower-sending me back to the shop about 1 1/2 miles away to repair it. After that I began again and mowed normally for awhile more then after moving to a steeper slope noticed the tractor slowed considerably on the uphill climb. Tractor is Husqvarna YTH18542, transmission TuffTorq K46bt. Notably, reverse is now faster than forward on the level, and has more notable torque. I checked the drive belt, and it is still like new, but sprayed belt dressing on it just in case. No improvement. I performed a transmission purge as per manual. No difference. Mower deck disengaged, no improvement. Anyone with an idea as to the cause? Does it sound like a bad transmission? It has likely less than 200 hours, when I got back to the shop the infrared thermometer read 130°F on the trans. The linkage seems tight, no obstructions, the forward throw is 1/2" to 5/8"


#2

H

hlw49

Check the mounting brackets to see if they are cracked and the front mounting bolts are not broken.


#3

L

larryuno

Hi HL, your comment made some things start to fall in place. Recently, I had a weld fail where the rear plate joins the two rails of the frame. Here attached is foto of the left trans bracket obviously moved. Also attached a foto of a sticker never noticed before that time, illegible, next to the failed weld, with a red slash. I live in Central America, and the salesman said this is a "special US lot" with Briggs and not Chinese motors, which are standard here. I bought in 2022.
I realigned everything as well as I could, and bolted the frame rail back to the rear box plate with automotive bolts, also bolting the bracket to where I thought it went. Since the grass refused to stop growing, I proceeded to test it and it appeared to work so I mowed for several hours.
What I would love to have is an accurate idea of how this machine goes together-the agency here was not helpful, they didn't even know how to see another of these "specials". Anyone with fotos (left rear frame mounts) and specs? For instance, how far should the "forward" valve throw open?

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#4

A

Auto Doc's

larryuno said:
Hi, the mowing day started normally. After about half acre one of my (rear) tire chains slipped free and caught in the mower-sending me back to the shop about 1 1/2 miles away to repair it. After that I began again and mowed normally for awhile more then after moving to a steeper slope noticed the tractor slowed considerably on the uphill climb. Tractor is Husqvarna YTH18542, transmission TuffTorq K46bt. Notably, reverse is now faster than forward on the level, and has more notable torque. I checked the drive belt, and it is still like new, but sprayed belt dressing on it just in case. No improvement. I performed a transmission purge as per manual. No difference. Mower deck disengaged, no improvement. Anyone with an idea as to the cause? Does it sound like a bad transmission? It has likely less than 200 hours, when I got back to the shop the infrared thermometer read 130°F on the trans. The linkage seems tight, no obstructions, the forward throw is 1/2" to 5/8"
Click to expand...
Pull the rear axle center caps off and look at axles shaft and keyway area. Make sure the axle did not shear the key when the wheel chain got caught up. Hopefully it did not tear up the rim and axle keyway area.

Torque and momentum can do some damage.

Why are you mowing with wheel chains on anyway... just curious.


#5

L

larryuno

Hi Doc, thanks..the keys and keyways are fine, just checked. I have had this farm for 35 years and have maintained it for nearly 19 of those with rider mowers, grass can be slick and the slopes are only doable with chains.


#6

A

Auto Doc's

larryuno said:
Hi Doc, thanks..the keys and keyways are fine, just checked. I have had this farm for 35 years and have maintained it for nearly 19 of those with rider mowers, grass can be slick and the slopes are only doable with chains.
Click to expand...
I recall also using wheel chains when I had to mow my uncle's property years ago in Virginia. He had very little flat ground. Of course, all the old riders also had manual shift geared transmissions back then.

This is shaping up to be an internal problem with your transmission. If it were a concern with the transmission oil, it would be weak in both directions.

Tuff Torq does make affordable repair kits for these, and they are not terribly hard to work on if you have some decent mechanical skills.

Teryl Fixes All and a few others have some decent videos on repairing these transmissions. A used unit is a gamble, and a new one can easily set you back well over $1100.00 dollars just for the part.


#7

A

Auto Doc's

Hi larryuno,

I did not see you reply to HL earlier. Hold off on my suggestions until you can get the shifted bracket and frame problem resolved and everything is sound and straight.

I did watch a couple of good videos about changing the fluid in these earlier, and there were some good, detailed pictures of the brackets.


#8

L

larryuno

HL, if you are still around, the right side mounting bracket is still attached; the left side bolt attached to the left side bracket has broken but is now directly above where the bolt was. Do you recall if the Husqv trans mount was a bolt coming all the way through from bottom to top and fastened with a nut, or?? The transaxle is maybe 3/16" ahead of where it was originally with respect to the frame rail, judging from the broken weld between back box and frame rail. Seeing it had worked for several hours that way, I am inclined to think the issue is internal to the transmission, can you see a way where that might not be correct?


#9

H

hlw49

here is a frame repair kit for the Husqvarna lawn tractors
www.ebay.com

MOWER FRAME REPAIR KIT FOR HUSQVARNA, POULAN, ARIENS, CRAFTSMAN .PATENTED | eBay

NO DRILLING, NO GRINDING AND NO SPECIAL TOOLS.
www.ebay.com


#10

G

Gord Baker

larryuno said:
Hi, the mowing day started normally. After about half acre one of my (rear) tire chains slipped free and caught in the mower-sending me back to the shop about 1 1/2 miles away to repair it. After that I began again and mowed normally for awhile more then after moving to a steeper slope noticed the tractor slowed considerably on the uphill climb. Tractor is Husqvarna YTH18542, transmission TuffTorq K46bt. Notably, reverse is now faster than forward on the level, and has more notable torque. I checked the drive belt, and it is still like new, but sprayed belt dressing on it just in case. No improvement. I performed a transmission purge as per manual. No difference. Mower deck disengaged, no improvement. Anyone with an idea as to the cause? Does it sound like a bad transmission? It has likely less than 200 hours, when I got back to the shop the infrared thermometer read 130°F on the trans. The linkage seems tight, no obstructions, the forward throw is 1/2" to 5/8"
Click to expand...
There is a linkage adjustment near the pedals that can be adjusted for optimum speeds both directions. Speaking about JD X320 and others. Try that Pedal height should be even or the Reverse somewhat higher. Stop mowing steep slopes. You can starve the engine from oil!


#11

L

larryuno

I am finally able to followup on my post. HL was correct when he said cracked frame and brackets: not only the left frame weld failed but the stress broke the right frame rail as well just by the deck lifter brackets. I got a welder to join things back together realigned as closely as possible, and now the mower performs as it did before, which is a relief. I still await a frame rail repair kit, so I can return with confidence, just hope the manufacturer will proceed with heavier frame material and only frame perforations actually needed, in future. I measured the frame rail thickness at 2.5 mm thick, which is barely 12 guage (about 1/16th inch).
Gord, your comment is noted, but I used a Poulan with a 19.5 hp Briggs for 15 years on that farm, and only repaired the usual Briggs compression release, head gasket, and magneto issues on the engine. Otherwise, a lawn tractor would be useless for my use, and the hills are not overly long, so I will take the chance, thanks. The sumps appear to be sufficiently deep on Briggs, unlike what I hear about the Loncin Chinese engine.


#12

G

Gord Baker

larryuno said:
I am finally able to followup on my post. HL was correct when he said cracked frame and brackets: not only the left frame weld failed but the stress broke the right frame rail as well just by the deck lifter brackets. I got a welder to join things back together realigned as closely as possible, and now the mower performs as it did before, which is a relief. I still await a frame rail repair kit, so I can return with confidence, just hope the manufacturer will proceed with heavier frame material and only frame perforations actually needed, in future. I measured the frame rail thickness at 2.5 mm thick, which is barely 12 guage (about 1/16th inch).
Gord, your comment is noted, but I used a Poulan with a 19.5 hp Briggs for 15 years on that farm, and only repaired the usual Briggs compression release, head gasket, and magneto issues on the engine. Otherwise, a lawn tractor would be useless for my use, and the hills are not overly long, so I will take the chance, thanks. The sumps appear to be sufficiently deep on Briggs, unlike what I hear about the Loncin Chinese engine.
Click to expand...


#13

G

Gord Baker

On some engines with an Oil Pump it is where the Pickup Tube is located that governs constant lubrication on slopes. Glad you have it running again.


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