Gunny65

I went out to warm the truck up (1979 DM685sx T/A Dump Truck) and noticed the tach and speedometer are not working...again. They started working for a few days and now they are not working again. No movement on either one. Suggestions on where to start my testing? I have two manuals but neither one covers gauges. If anyone can also point out where I could get a manual for the electronics end of it I would appreciate it. Thanks.

It took me a while but I got the new clutch in. I put in the Eaton 9 spring ''Easy Pedal'' clutch. Yes, I went ahead and paid a local guy to put it in. He was backed up so it took a while but I now have a new clutch. Thanks for all the suggestions. Now I need to get some other things working. It is fully usable at this point but there a lot of little things that need attention. I will make new posts for those questions. Again, thanks everyone.

Yep, it is the swivle, Ex-railroad dump truck. I thought T/A meant Tandem Axel? Is that correct? At one time I was thinking triple axle but later reading led me to believe it is tandem. Correct me if I am wrong. Thanks. The transmission is connected via linkage rather than cables. External linkage anyway. Not sure inside but it looks like the triple shaft "V" shape that JoeH described. I did have a helper but he had to move for job purposes. Now I do things alone but with a lot of safety/self-preservation planning. I will buy a trans jack and modify as noted above. Make a cradle on the jack so to speak. I MAY have a diesel engine mechanic that could help but he is pretty busy. We will see. I didn't see to much oil leakage around the rear main but thanks for the heads up. Good ideas on what to accomplish while I have the engine more accessible. The good thing is this truck model does not have a passenger seat so I don't need to remove that. I need to clean the cab out any way to access the panel you are referring to. That would not have crossed my mind, I doubt. Thanks. I planned on removing the prop shaft, lowering the trans, securing it, and then doing the clutch work in between the open space if possible. I think it is possible based on looks under the truck. I believe I found the proper E7 flywheel. Not as expensive as I had expected. That was nice. Still have not found a clutch plate, springs, etc. I need to do more reading. Thanks everyone for the input/help. All of it helps. BTW, this operation isn't going to happen till spring but I need to research and buy in preparation for the job.

I did find the switch and it is bad. It is right under the floor board, outside of the cab, where the brake pedal air hoses connect. When I hooked the wiring back up, it just made the brake lights come on at all times. Thanks all.

Joey, I like the idea of changing to more readily available parts that fit. I need to take it apart anyway so why not? I will look around the posts here and see if I can find more info on what you are describing. Thanks. JoeH, I am pretty sure I can do the repairs. I did rebuild a 700R4 once. The weight of this trans is the biggest issue. I can do the work, it is the crashing down weight thing that worries me. LOL. I will need to invest in some tools specific to this operation though. I have no clutch tools at all. I have Lots of tools, just never worked on clutches before. It has always been: how much does the repair cost, can I buy the tools needed and so it myself cheaper than it would cost to pay someone? Then I do it myself and end up with more tools. Win, win for me.

I have a 1979 DM685sx T/A Dump Truck. The clutch is worn to the point it can no longer be adjusted and it is slipping. I believe I have the MaxiTorque Transmission (TRL107) with MACK clutch. The ID plate says: (REGU.S. MACK Maxitorque Transmission PAT.OFF) There are no other numbers or markings on the plate (top left side rear of trans housing). Where should I go to buy clutch parts for this year and model? I found a service manual that will help me remove and install the clutch. Any pointers would help as well. Thanks!

I came here to learn so no big deal to me if it goes further than my intended questions. This is all helpful. I read up on how to adjust the clutch engagement and clutch brake. Hopefully I can get to it in the next few weeks. You know, before the snow falls. I have to work on it outside so weather is a factor. Hopefully the clutch isn’t to far gone to adjust it properly.

Finally, here are some pictures.

Soooo, I was looking to get a repair and/or service manual for this truck. $304.00??? Totally ridiculous. I found some others that I Think are for the correct years but not sure. Still kind of expensive but better. Anyone know where to get manuals for my truck in a more reasonable price range?

Not sure where the brake light switch is located. It isn’t in the cab. Pictures later that might show it but not sure.

JoeH, You are correct. I am not very familiar with them. I used double clutch when I was a young man in the military but that was a long time ago and not often. This trans is a single stick, reverse, with 5 gears. I did try the double clutch method but either I didn't do it right or it just didn't work. I think I pushed the pedal to the floor when trying the double clutch. I also tried a quick push/release to disengage, and then another quick push/release to re-engage. I tried to keep the rpms up when double clutching but no luck for me. I never tried to change gears without using the clutch. I still have some learning to do. LOL. Oh, and you are correct the way I adjusted the clutch pedal was not correct but it was just enough to get me home. An emergency fix. My knee was up by the steering wheel after moving the bolt about a quarter inch. It wasn't comfortable. From the beginning, the clutch pedal had no play. It was under tension immediately and disengaged, in about that two inches, of the initial movement. I assumed that was why the clutch was slipping when I started up the first major hill we came to. Unfortunately, I didn't notice the slip until I saw some smoke and smelled it. I thought the truck was just bogging down due to the hill. I will read up on how to adjust the clutch correctly as I had no idea. Thanks for the heads up. I did not know the clutch brake is only used when stopped. I thought it stopped them while driving as well. You know, to synchronize when shifting. Is this only in older trucks? Big trucks? or all trucks that use a clutch? Thanks for the help. That is exactly why I come to these types of forums when I get a new to me piece of equipment.

I got the truck home today. Drove it 115 miles with no break downs. I couldn’t find anyone coming this way to deliver it so just took a chance and drove it. I had to adjust the clutch pedal as the clutch was slipping. I can’t down shift at all. Trans won’t stop rotation when down shifting and just wants to grind. Clutch started slipping going uphill. That is when I stopped and adjusted the clutch pedal return bolt just to make it home. Lots of little things wrong. Rpm, speed and fuel gauges do not work. Got the brake lights working. Bad wiring and rusty bolts were the problem there. Anyway, it is home. More pics coming in a day or two. Guess I should start a thread in the proper forum after posting pics. Thanks everyone for the welcome and help.