Ammco 4000 longtravel g/box adjustment not working properly,variable speed adjustment works slowly,then when increased starts to work backwards

If you've replaced the variable speed unit in your Bosch 11318EVS SDS-max Demolition Hammer and the variable speed is still not working, there could be a few potential reasons for this issue. Here are some steps you can take to troubleshoot and address the problem:

1. Check Wiring Connections: Ensure that all wiring connections related to the variable speed control are properly connected and secure. Loose or damaged wires can disrupt the variable speed function.
2. Control Switch: The control switch itself could be faulty. Test the switch to make sure it's functioning as intended. Use a multimeter to check for continuity across the switch terminals in different speed settings.
3. Speed Control Potentiometer: The potentiometer, which is responsible for adjusting the variable speed, could be malfunctioning. Test the potentiometer with a multimeter to ensure it's changing resistance smoothly as you adjust the speed.
4. Electronic Control Board: The issue could be with the electronic control board that governs the variable speed function. Inspect the board for any signs of damage, such as burnt components or solder joints.
5. Brushes and Carbon Motor Contacts: Worn brushes or carbon motor contacts can affect the motor's performance and, consequently, the variable speed control. Check the condition of the brushes and motor contacts and replace them if necessary.
6. Power Supply and Voltage: Ensure that the tool is receiving the correct power supply and voltage. Incorrect power supply can affect the tool's overall performance.
7. Manufacturer's Support: If you've exhausted your troubleshooting efforts and the variable speed is still not working, it's advisable to contact Bosch customer support or a professional tool technician. They can provide more specific guidance based on the model and diagnose the issue accurately.
8. Professional Repair: If the issue is complex or involves internal components, it might be best to seek the assistance of a professional tool repair technician who has experience with Bosch power tools.

Remember that working with power tools and electrical components carries inherent risks. If you're not comfortable or experienced with tool repairs, it's recommended to seek professional assistance to ensure safety and prevent further damage to the tool.

You will need to look inside the "Cross Feed" gear box assembly (7751). You may only need a replacement "Shear Gear" (7996). I've added two photos to help.

there is not info to be able to give a definite answer
to work it out
you have top know the diff ratio, wheel tyre circumference to be able to work from rpms of the engine to road speed
However as a pointer, most cars will be around 3200 rpms at 60mph as this will be direct drive and od causes a drop in rpms
Being an automatic find yourself a good section of low traffic road and start from stop slowly increase the rpms and watch the rpms. keeping the accelerator steady you will see when the auto changes by a drop in rpms. slowly increase road sped until you see the next drop in rpms and so on. Over drive normally comes in around 55 mph or around 3000rpms
I would think that it is working because 3500rpms at 75mph is reasonable rpms to be expected. If it wasn't working I would expect the rpms to be around 3800 to 4000.at 75mph

Start with 1-1.5 turn out . Adjust, slowly, high speed first then high speed screw first, screwing until RPM increases then slows open back up, slightly. Do low speed the same way at idle.

I guess that you have a manual transmission. If that is the case you have a clutch on the way out. Slow slippage that gets worse as the plate gets hotter. If an automatic it is possible that the overdrive is not holding due to low pressure in the box. Have a pressure test done on the box--- have the fault codes read. From experience 120 kph is around 3200rpm for most cars and the 800 rpm difference indicates that the o/dive is not working as it should.

check the other variable pulley on the other end

I am a brake lathe technician.

To change the drive belt on an Ammco 4000, you must first remove the 90 degree angle PTO (power take off) gear assembly which is driven off the back of the big pulley. Two small allen head screws hold it tight.

Pull the PTO gear assembly out of the disc-feed gearbox. If there are colored shims between the gearbox and the PTO assembly, you must make sure not to loose. If they drop off, be sure to replace them with a dab of grease.

Rotate the red knob at the back of the machine and the motor assembly will unlock and rotate upwards. Replace the drive belt.

To adjust the drive belt tension properly--loosen the 3/4 inch nut on the back of the machine, and the motor will drop down. Tighten the 3/4 inch nut and then rotate the red knob back until the belt is taught.

Replace the PTO gear assembly--making the rotating part with the protruding pin is centered on the big pulley. Tighten the allen head cap screws.

Turn on the machine. If the PTO is making noise--you have not correctly is correctly. Repeat the centering process until the machine runs without rattling or vibration.

I am not aware of any speed controller on this tool. what I would do is unplug tool and turn it on its backside and look at the switch to see if possibly burnt causing problems.

http://cgi.ebay.com/ebaymotors/Ammco-4000-Brake-Lathe-Operating-Manual_W0QQcmdZViewItemQQitemZ360197546157QQptZMotorsQ5fAutomotiveQ5fTools

You might try buying a manual for it. There is one on E-bay right now. might be $14.00 well spent.

Hope this helps.

Bob

I had a customer bring me a saw with this same problem. All components tested OK on my growler. I went on a limb since the speed control and the armature tested OK. I replaced the feild since to me it seemed to be the only component that could cause the motor to run in reverse. Tool now works properly and have had no more problems with the tool.