Riding mower problem

[Cliffh]

I've got a Husqvarna YTH2348 with ~870 hours on it.  It has a hydrostatic transmission, and I replaced the original motor with a 27hp B&S motor.  Over the last 8 to 10 hours of use it's developed a problem backing up.  It drives just fine going forward; it will back up on level ground with very little power, it won't back up even the slightest incline.  It does have a tendency to jump when starting forward - sort of like I'd mashed the pedal - even when I try to ease into it.

Because I've modded it to my liking and I've got a lot of spare parts for it, (and my truck just puked the motor, requiring purchase of another truck) I'd like to keep it.  But only if the repair isn't going to cost an arm and a leg.  I'm confident I can do any repair(s) necessary, but I need to have an idea of what to look at/test.

I've never replaced the drive belt, but, since it works fine going forward, I'm thinking the belt's probably OK.  I haven't changed the belt 'cause it's a bitch to do, and I don't have the time to waste "fixing" something that doesn't need fixing.

[Jim147]

I would still look at the belt first. I had an oil seal go out on my Cub this spring. Covered the drive belt in oil. It would still go forward slower then normal but wouldn't back up.

[cordex]

Drive belt went out on my mower last weekend.  I got the new one but the bolt that connects the electric clutch to the drive shaft is really tough to remove.  I'm letting some oil soak in, but since I can't turn my mower upside down it is having to soak up, not down.

[Cliffh]

Guess I'll be looking at the drive belt...

I've been using a pair of DYI ramps for maintenance, this sounds like a good time to get a real mower lift.

[RoadKingLarry]

My old AYP/Craftsman began getting weak in reverse and I was concerned that the transmission was about worn out.
When I bought my new Husqvarna this Spring I gave the old one to my daughter and son in law.
SIL and I went through and replaced all the belts and gave it a good going over
After the ground drive belt was replaced the suspected transmission problems went away.

[Cliffh]

I finally got the parts, tools & time to look at it today.  The drive belt was sort of the problem.

The hydraulic pump is driven by one belt from the engine to the top of the rear axle assembly.  The rear axle assem. is mounted to the frame with 2 bolts on either side, bolts go through the axle housing and a flange off the frame.  There's also a cross-brace just forward of the axle housing, two bolts go through it and into the axle housing. 

When the heads break off the two cross-brace bolts the housing will try to rotate either up or down depending on which direction you're traveling.  If you're going forward, the front of the housing rotates up, which applies more pressure on the belt driving the pump.  If you're reversing, the front of the housing rotates down, loosening the pressure on the belt, allowing it to slip and stop driving the pump, which explains the loss of reverse.

This back & forth rotation also causes a *lot* of stress on the two mounting plates on the sides.  That stress then causes both plates to bend and crack.

I hope to have all the bending, welding & bolt removal/replacement completed tomorrow.  I'm also adding a few pieces of 1 1/2" angle to reinforce the mounts. While I'm at it, I'll be looking to see if the cross-brace/bolt can't be strengthened somehow.

I'll go ahead and replace the belt while it's apart....

I do like the new jack.  I got the 350# unit:  https://www.amazon.com/gp/product/B06XTD5Y9X/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1  It's pretty lightweight, and the wheels are useless on anything other than a smooth concrete floor, but it lifts my mower just fine, it'll make changing the blades and cleaning the deck a lot easier.