Transmission trouble

[The Collector1]

Hi to everyone on the forum,
I was wondering if anyone could help me,I received a Ford Aeromax for my Birthday in October and everything was fine, it ran good and shifted well for a first 3 speed build, but my trouble started when I received my box trailer for xmas, now the trucks tranny slips in 1st gear and sometimes in 2nd.
Ive removed the tranny from the truck but I havent had time to fully inspect it, I dont want to damage it any further if it is damaged and if I have to replace parts how hard is it to order parts for it, if anyone can help the new guy I would be so grateful.

[mrfish55]

Are you using the multi function unit?

[The Collector1]

Yes Im using the MFU and I have the stock 540 in it, I have a Carson Modelsport motor but I dont want to put it in with the tranny problems, and thanks for the quick reply.

[mrfish55]

There has been a number of people having problems when using a trailer with the mfu. When you couple the trailer to the truck does it make the coupling sound? The MFU changes power settings when towing a trailer. I was having the same problem when I set up my first MFU (felt like tranny was slipping). The set up procedure for the speed controller is not that well written, when doing the initial setup make sure all your trims are neutral and servos are set normal, after setup you can reverse servos and adjust trim. If you have a spare speed controll try that instead of the mfu to make sure that is where the problem is. Good luck, Dave.

[Mouton]

Albeit the switch in the fith wheel does increase the current flow to the motor it does not affect the way the servo that operates the gearbox in any way.

As mrfish55 points out your trims need to be in neutral when you change gears. I assume that is the case for you too? If so, it does sound as if you should recheck your gear servo linkage. From what you describe I would suggest that the your problem is that the servo that operates the gearbox does not properly select first and second gear. Your trailer adds more weight to pull, which means that if the gearbox is not fully in gear it might more easily slip out of gear than when driving without the trailer.

Does the gearbox linkage move all the way out and in as the build manual shows? My guess is that you need to increase the servo throw towards first gear. You can try this by adding a slight left trim with the gear servo channel. Do not overdo it with the trim as that will change the motor rev./running setting.

If this solves the problem with first gear you must increase the servo throw in that direction. That can either be done by increasing the EPA (End Point Adjustment) on your transmitter if it has such a funtion or buy using a longer servo horn on the gearbox servo.

Keep in mind that only a few millimeters wil do the trick. As you said it does not always slip out of gear only little adjustment is needed. When first and third gear work as they should, second gear will too (as long as the servo is at its neutral setting then).

I hope this helps.

[The Collector1]

I opened the tranny and found nothing that I can see so I will try to adjust the linkage and see if that works I will keep you guys updated. Thanks