AD21 gear problem

[Daniloncho]

]Hola tengo un ad21, con problemas en caja de cambio , a veces no entra la directa y cuando coloco reversa parece que aumentan los problemas. Como desarmo la selectora que tipo de solución tengo.
Gracias

[Nancy]

Unfortunately, I don't speak Spanish, but I ran the above post through Google Translate:

Hello, I have an ad21, with problems in the gearbox, sometimes the direct gear does not enter and when I put reverse it seems that the problems increase. How do I disassemble the selector, what kind of solution do I have?

[dkirsop]

The AD21 transmission uses two precisely machined springs to convey power through the transmission.

In forward mode, the engine output shaft is gripped by the smaller spring which transmits power to the transmission shaft. In neutral the gear selector causes a plunger to descend and engage a tab on the end of the spring. The spinning action of the engine unwinds the spring and the connection between the spring and engine output shaft is lost. Note that the clearance between the spring and the shaft is very small when in neutral. The engine should only idle in neutral for 10 minutes or less. Long idle times will cause the spring to overheat and develop slippage. If this occurs the spring will need to be replaced.

small spring.jpg

In reverse mode, a second spring engages the planetary gear drum and causes the propeller shaft to reverse its direction of rotation. Because reverse is used less often and the spring is larger it is unlikely to be damaged. Damage is most likely to occur from overloading the transmission when in reverse.

large spring.jpg

There are 3 possible issues causing your problems.

1. The wrong oil is being used in your engine. It is important to only use SAE 30W oil rated for use in diesel engines. Use of a multi-weight or synthetic oil will give rise to slippage in the transmission. If this is the case I suggest you consider flushing the oil from your engine with 3 quick oil changes limiting the engine use time between changes between 5 and10 hours.

2. The plungers in your gear selector mechanism are worn and not engaging with the tabs on the clutch springs. Easy to inspect but fussy to repair. Try rotating the engine manually selecting the various gears to see if the selector is engaging with the springs and causing the shaft to spin in the proper directions as well as selecting neutral.

Remove the gear selector and see if the two plunger tabs are in good condition or worn. Albin Motor can provide new plungers if necessary.

3. In my experience the spring most likely to wear is the smaller one that connects the engine output shaft to the motor. In this case you will need to remove the transmission and replace the spring. Before removing the transmission make sure to place it in neutral and rotate the engine manually to ensure the spring is free from engine output shaft.

Before removing the transmission replace two of the upper bolts with 3 inch long 5/16 inch bolts with the heads removed. These will support the weight of the transmission as you slide it back from the engine and will also help suport and align the transmission when you put it back together.