Speed drop in third gear for no apparent reason - 8-speed

[Shrek 12]

Hello everyone! I'm a new owner of a C-85.  I'm still learning and reading about these tractors.  I've run it a few times mowing the lawn mostly in second gear.  I don't have any problem shifting gears. When I'm done mowing, I raise the deck, disengage the PTO and shift to 3rd (hi) to scoot back to the garage. The tractor accelerates normally, but after a few seconds the speed just falls away to a complete stop. There's no change in engine speed.  Any thoughts? What should I start checking first.  I have tried searching this forum.  Thanks in advance!

 

Matt

[gwest_ca-(File Mod) 11,096]

Welcome to the forum.

My guess is your drive belt is slipping.

Like a friction clutch in any vehicle the higher the gear the more force it places on the drive components. So it will slip in 3rd before it slips in 2nd.

Belt may be worn too narrow to fit the pulleys or the pedal return spring on the left side is weak.

 

Garry

[clueless 3,011]

Also are you shifting gears without coming to a complete stop, that's a no no .

[Shrek 12]

I shift when stopped and try not to force it.  Is there an adjustment for the belt tension?  I'll start reading through the manuals tonite after work.

[gwest_ca-(File Mod) 11,096]

No adjustment for belt tension.

There is an adjustment on the rear of the rod from the pedal but it just positions the pedal to suit driver height.

 

If you look from the rear of the tractor between the left tire and the transmission you should see the return spring. It hooks into a cast iron web above the left axle housing.

 

Garry

[Ed Kennell 38,646]

The tension spring that Garry is referring to  pulls on a lever that rotates a cross shaft to the belt idler/tension pulley on the right side.

This lever on the left side is pinned to the cross shaft with a 1/8" roll pin.   I have found this pin sheared on several tractors causing a condition similar to yours.

Put a mark across the end of the shaft and lever to see if there is any change in the position of the lever on the shaft.

Other possibilities are a missing key in the transmission input pulley or an axle hub.

 

Oh, I almost forgot       to the 

Edited June 13, 2020 by Ed Kennell

[Shrek 12]

2 minutes ago, Ed Kennell said:

The tension spring that Garry is referring to  pulls on a lever that rotates a cross shaft to the belt idler/tension pulley on the right side.

This lever on the left side is pinned to the cross shaft with a 1/8" roll pin.   I have found this pin sheared on several tractors causing a condition similar to yours.

Put a mark across the end of the shaft and lever to see if there is any change in the position of the lever on the shaft.

Other possibilities are a missing key in the transmission input pulley or an axle hub.

ok thanks!

[Shrek 12]

On 6/13/2020 at 12:12 PM, Ed Kennell said:

The tension spring that Garry is referring to  pulls on a lever that rotates a cross shaft to the belt idler/tension pulley on the right side.

This lever on the left side is pinned to the cross shaft with a 1/8" roll pin.   I have found this pin sheared on several tractors causing a condition similar to yours.

Put a mark across the end of the shaft and lever to see if there is any change in the position of the lever on the shaft.

Other possibilities are a missing key in the transmission input pulley or an axle hub.

 

Oh, I almost forgot       to the pa

Spring is in place. I painted a mark both on the clutch shaft/lever and across the drive shaft/pulley.  I operated the clutch several times. no movement on the mark of the clutch shaft/lever.  I'll report back on the drive shaft/pulley.  Is there a way to measure the wear on the drive belt? Width and depth?

[WHX?? 49,159]

 

Another thought is popping out of gear. What do you have to do to get it moving again? If you have to shift it back into 3rd yes that is what's happening. 

1 hour ago, Shrek said:

Is there a way to measure the wear on the drive belt? Width and depth?

Not accurately unless you have a belt gauge. Visual inspection & replace if in doubt. 

[gwest_ca-(File Mod) 11,096]

One thing you could try is when you are loosing speed put your toe under the clutch pedal or heel over the pedal and put it back to see if that restores the drive.

 

If you get a new belt and it does not solve the problem keep it for a spare.

 

Garry

[Tractorhead 9,065]

6 hours ago, Shrek said:

Spring is in place. I painted a mark both on the clutch shaft/lever and across the drive shaft/pulley.  I operated the clutch several times. no movement on the mark of the clutch shaft/lever.  I'll report back on the drive shaft/pulley.  Is there a way to measure the wear on the drive belt? Width and depth?

 

Firstly  to 

agree to the others! 

 

beginning from cheapest to check

good belts can normally visual seen they don‘t touch completely the ground of the Pulley inside.

they have primary touch the flanks they be responsible for the transmission friction.

is the belt too old it can dry out and when it gets warm while in use it develops a slippy surface nearly like soap.

but that can‘t be felt.

 

 

If you look along inside the belt in direction to the Pulley, you can see if the belt touches the ground of the pulley or not.

If the belt touches the ground it seems a worn belt or even a wrong belt size when engaged.

 

if you shift back after standstill happens again in 2 nd gear, does it move than as before?

 

if it moves as before than i would also doublecheck firstly the strenght of the Spring on the Beltspanner if it is strong enough.

there must be some force behind, otherwise the belt can slip on higher Load over the pulley’s what the 3rd gear can allready be.

 

Also a too small belt can cause that if Belt touches the ground and not the flanks of the Pulley.

 

if that all seems ok, i would check the Pulley‘s next, if the key’s are broken.