Dieselfixer Posted September 24, 2022 Share Posted September 24, 2022 Hi All I have a 1986 DM685S with a Maxitorque extended range transmission. I'm trying to identify the pto that is on it. It mounts to the back of the trans. If anyone can help identify it or maybe has 1 for sale please let me know. Thanks, Al Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/ Share on other sites More sharing options...
terry Posted September 24, 2022 Share Posted September 24, 2022 (edited) The rear mounted PTO'S on that trans that i have seen were run on one of the countershafts, had a special slot in the countershaft to turn the PTO. terry Edited September 25, 2022 by terry 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510239 Share on other sites More sharing options...
mechohaulic Posted September 25, 2022 Share Posted September 25, 2022 I didn't think the rear mounts had that many variations . have mounted a few but that was years ago .as with everything else back then no one paid much attention to keeping numbers or all the stuff would be collectable 40-50 yrs later. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510261 Share on other sites More sharing options...
Joey Mack Posted September 25, 2022 Share Posted September 25, 2022 Is that a gear reduction setup? I don't recall that style. Heck, I thought with the 107's you could put the aux in neutral, and select a gear in the main, for different pto speeds.. damn I'm rusty... 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510264 Share on other sites More sharing options...
mechohaulic Posted September 25, 2022 Share Posted September 25, 2022 purpose of the rear mount P T O's on the maxitorque was to enable the truck (dump) to drive and raise the body same time . such as spreading asphalt etc. aux in neutral would allow 5 different speeds for a body to raise but couldn't move. pto in 1st too slow, 4/5th truck can't drive. rear mount was constant operation same as old style side mounts. those were the days of many spreader boxes towed by truck unlike the high tech self propelled asphalt spreaders of today. boy do I have many many hrs on those spreader boxes. LOL Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510266 Share on other sites More sharing options...
mechohaulic Posted September 25, 2022 Share Posted September 25, 2022 5 hours ago, terry said: The rear mounted PTO'S on that trans that i have seen were run on one of the countershafts, had a special slot in the countershaft to turn the PTO. terry early rear mounts had a shaft out similar to the floating axles . always mounted on the bottom counter shaft ; allowing oil to flow through and the lower counter shaft had a hole in the middle with splines for the PTO shaft to mesh with. very simple install, no shims /spacers or backlash setting like the old side mounts. only thing that had to be done (with extreme caution) was to slightly pull the countershaft out ;it was tapered and turn it 180 degrees. too far and the internal shims fell off shaft and someone's ass was grass. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510269 Share on other sites More sharing options...
terry Posted September 25, 2022 Share Posted September 25, 2022 11 hours ago, mechohaulic said: early rear mounts had a shaft out similar to the floating axles . always mounted on the bottom counter shaft ; allowing oil to flow through and the lower counter shaft had a hole in the middle with splines for the PTO shaft to mesh with. very simple install, no shims /spacers or backlash setting like the old side mounts. only thing that had to be done (with extreme caution) was to slightly pull the countershaft out ;it was tapered and turn it 180 degrees. too far and the internal shims fell off shaft and someone's ass was grass. Yeah i wasn't sure if the shaft had a slot or splined. terry I have shimmed alot of side pto's shim the idler gear to the trans then take off and shim to the pto then assemble! 2 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510299 Share on other sites More sharing options...
Joey Mack Posted September 25, 2022 Share Posted September 25, 2022 I worked on a few of them many years ago.. the bottom counter shaft has splines in it,, the other 2 do not, so when building the tranny you just need to put the #3 shaft in the bottom.. jojo 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510300 Share on other sites More sharing options...
mechohaulic Posted September 25, 2022 Share Posted September 25, 2022 36 minutes ago, terry said: Yeah i wasn't sure if the shaft had a slot or splined. terry I have shimmed alot of side pto's shim the idler gear to the trans then take off and shim to the pto then assemble! the idler on side mounts was usually there to set the pto in opposite rotation. Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510301 Share on other sites More sharing options...
terry Posted September 25, 2022 Share Posted September 25, 2022 8 hours ago, mechohaulic said: the idler on side mounts was usually there to set the pto in opposite rotation. On all the the older ones triplexes and so, the countershaft gear was so small it need that idler gear to reach it. and then most pumps had two stubs to hook your shaft to for what direction you needed to go. terry 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510330 Share on other sites More sharing options...
fjh Posted September 25, 2022 Share Posted September 25, 2022 On 9/24/2022 at 11:44 AM, Dieselfixer said: Hi All I have a 1986 DM685S with a Maxitorque extended range transmission. I'm trying to identify the pto that is on it. It mounts to the back of the trans. If anyone can help identify it or maybe has 1 for sale please let me know. Thanks, Al Picture 1 is driven off the main box counter shaft and has five selectable speeds if I recall! On a 12 sp trans ! Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510339 Share on other sites More sharing options...
Dieselfixer Posted September 26, 2022 Author Share Posted September 26, 2022 The problem I'm having with it is when trying to dump a load the pto is popping out of gear. If the truck is empty the body will go all the way up with no problem. I'll have to take it apart and see what's going on with it. Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510370 Share on other sites More sharing options...
Joey Mack Posted September 26, 2022 Share Posted September 26, 2022 probably the sliding clutch inside the PTO housing.. I assume it is cable operated? Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510371 Share on other sites More sharing options...
fjh Posted September 26, 2022 Share Posted September 26, 2022 12 minutes ago, Dieselfixer said: The problem I'm having with it is when trying to dump a load the pto is popping out of gear. If the truck is empty the body will go all the way up with no problem. I'll have to take it apart and see what's going on with it. So is it an air operated or cable operated?as pictured? The should be a stop on the linkage there ! I believe it’s a sliding gear in there! I have changed the shaft on these with out removing the whole lump but it has been years! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510373 Share on other sites More sharing options...
mechohaulic Posted September 26, 2022 Share Posted September 26, 2022 by the picture seems air operated. indicates problem with internal pto . air cyl wouldn't know difference if body empty or loaded. I don't know why it would make a difference either. as joey stated worn slide clutch ,same as trans pops out of gear when sliders are worn. looking at the picture, 1- a little lube on linkage would help;2- remove linkage check see if cyl is throwing far enough. 3- adjust the throw to fully engage slide clutch might be a quick fix. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510374 Share on other sites More sharing options...
mechohaulic Posted September 26, 2022 Share Posted September 26, 2022 enlarge picture 3 of the air cyl;; linkage from PTO (flat bar) looks to have worn pin hole on back side. measure the distance from pto to welded bar. remove linkage see if you can manually pull pto linkage out further. might just be worn external parts 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510375 Share on other sites More sharing options...
mechohaulic Posted September 26, 2022 Share Posted September 26, 2022 also looks to be wrong size pin in the linkage;; doesn't help🙃 . worn pin hole, wrong pin; cyl doesn't have 3 -4 in throw. LOL 2 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510376 Share on other sites More sharing options...
mechohaulic Posted September 26, 2022 Share Posted September 26, 2022 to be around when those P T O's first came out ; talk about feeling old . 2 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510377 Share on other sites More sharing options...
Joey Mack Posted September 26, 2022 Share Posted September 26, 2022 I just looked again, I can see daylight through the pin hole in the lever.. Definately an issue there.. If a lever isnt available, weld it up and re-drill it... then use a new pin... that wear will definatley cause improper engagement of the sliding clutch... jojo 2 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-510378 Share on other sites More sharing options...
Dieselfixer Posted October 8, 2022 Author Share Posted October 8, 2022 Thanks All I will look into the linkage first. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-511348 Share on other sites More sharing options...
mechohaulic Posted October 10, 2022 Share Posted October 10, 2022 be great to update and let us know what you find/found. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-511421 Share on other sites More sharing options...
Joey Mack Posted October 10, 2022 Share Posted October 10, 2022 I second that motion..... 2 Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-511422 Share on other sites More sharing options...
Dieselfixer Posted December 12, 2022 Author Share Posted December 12, 2022 Haven't had a chance to work on it yet. I will update soon. Quote Link to comment https://www.bigmacktrucks.com/topic/70476-pto-help-needed/#findComment-518048 Share on other sites More sharing options...
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