Full Floater Posted August 28, 2015 Share Posted August 28, 2015 Reverse is becoming more troublesome to engage lately on my RS600. I have a 12 speed with the air selector reverse. Im having to try far too hard to get it to engage reverse. I'll inch it around in forward gears a bunch, in and out of the clutch and other range selections until finally it will grab reverse. I don't hear any air leaks. So where can I start looking for an issue, I have just ordered a new air line filter, Mack# 2MD3131. After that, im lost. I have attached a picture of the air solenoids/valves on top of the tranny. Which one activates reverse? Does anyone have any tips in engaging reverse?Yesterday I had to free wheel down a small hill because I couldn't get it into reverse. Other times it goes in as easily as it used to. But those times are becoming fewer and further between. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/ Share on other sites More sharing options...
Challenger Posted August 28, 2015 Share Posted August 28, 2015 The round cylinder on the driver side is the direct/lo cylinder. The square one on the passenger side is the neutral/reverse cylinder. The air fitting on the side of the neutral/reverse (passenger side) is the reverse supply air line. You could remove the airline from the reverse cylinder and select neutral/reverse and see if the supply is quick or slow. If the air supply seems ok, you may need to remove the top cover and replace all the orings in the top cover shift cylinders. It looks like you have plenty of space above the top cover to remove it. There is a oring kit that comes with all the rear top cover orings. Also replace your little circle stone breather thats on the bottom of the direct/lo cylinder (round cylinder on driver side)If the air supply is slow or intermittent, you could have a bad inversion valve or shifter. The airline from the reverse fitting runs back to the inversion valve. Alot of problems with air selection are the top cover orings. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-301824 Share on other sites More sharing options...
Full Floater Posted August 28, 2015 Author Share Posted August 28, 2015 Thanks for the insight!!! Is the oring kit a "kit" that I need to order or are they standard orings? Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-301827 Share on other sites More sharing options...
Challenger Posted August 28, 2015 Share Posted August 28, 2015 I would think most Mack dealers have the kit in stock. Its just a bag of orings. I dont remember the part number but someone here knows it, if not the Mack parts guy will. The orings are made for the trans, they're not standard orings. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-301829 Share on other sites More sharing options...
mrsmackpaul Posted August 28, 2015 Share Posted August 28, 2015 put an air gauge in the air line supplying the reverse air ram and see what the air pressure is might have a crook regulator I think its meant to be around 50 - 60 psiPaul Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-301836 Share on other sites More sharing options...
j hancock Posted August 28, 2015 Share Posted August 28, 2015 Thinking the o-ring kit is 207SH32. Don't know the new volvo number. About $30.00, Double check number with the dealer. Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-301837 Share on other sites More sharing options...
Full Floater Posted August 29, 2015 Author Share Posted August 29, 2015 Ill check that, thanks Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-301866 Share on other sites More sharing options...
Full Floater Posted August 29, 2015 Author Share Posted August 29, 2015 And thanks for the part number Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-301867 Share on other sites More sharing options...
Full Floater Posted August 29, 2015 Author Share Posted August 29, 2015 And another quick question....should the clutch be in (disengaged) or out (engaged) when attempting to select reverse? I have not been able to diagnose anything yet....darn work getting in the way. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-301926 Share on other sites More sharing options...
Challenger Posted August 29, 2015 Share Posted August 29, 2015 While driving or moving, clutch pedal in (disengaged). Troubleshooting, truck just needs full air pressure. Truck doesnt need to be running. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-301932 Share on other sites More sharing options...
Full Floater Posted August 31, 2015 Author Share Posted August 31, 2015 Ok so I replaced the air filter/breather and removed the air line from the round reverse cylinder and found lots of pressure from the air line when reverse was selected on the shifter, didn't even put a gauge on it as I no longer thought that pressure was an issue. I sprayed a little (not much) WD-40 down into the reverse cylinder in the air fitting, hooked the air line back up and reverse is now engaging first try again. Did one small job with the truck and it worked fine the entire time. So, im not sure if the breather may have been clogged or the WD-40 lubed things up a bit or both; but its working again. Im still going to order the o-ring kit just in case.Thanks again. I will stay posted with how it works over the next while. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-302125 Share on other sites More sharing options...
Challenger Posted September 1, 2015 Share Posted September 1, 2015 The round cylinder on the driver side is the direct/lo cylinder. This cylinder will have air to both direct and lo fittings while selecting reverse, this puts them in neutral so reverse can be selected. The square cylinder on the passenger side is the reverse/neutral shift cylinder. The fitting on the passenger side is reverse and the one on the rear is neutral. Just wanted to clear that up.If the breather is clogged it could cause a delayed reverse because the direct and lo wouldnt go into the neutral position correctly. Sounds like you're good to go. If it happens again replace the orings. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-302219 Share on other sites More sharing options...
Full Floater Posted September 13, 2015 Author Share Posted September 13, 2015 Yeah im going to have to do those orings quick. It won't engage at all when its hot now, once it cools down it seems to work fine. Got stuck today nosed into a wall and couldn't get it in reverse, had to come back later and try. Drove it home and same thing. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-303537 Share on other sites More sharing options...
Solution Challenger Posted September 14, 2015 Solution Share Posted September 14, 2015 When you buy your oring kit ask the Mack parts guy to print out the rear top cover illustration page. You can use this as a guide for reassembling. Or just mark every piece in order to help you while reassembling. Its not that difficult, but sometimes I have to break out the book because I forget which way parts face. Time seems to be important for you, so every bit helps. Once you have the cover off, there is an interlock pin inbetween the cylinders. This allows only one cylinder to engage. The pin has to hold one cylinder shaft for the other to come out. So if you cant pull a shaft out, its because the other shaft isnt in the correct position. Just a heads up so you can save time. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-303685 Share on other sites More sharing options...
Full Floater Posted September 14, 2015 Author Share Posted September 14, 2015 Thanks again!! Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-303733 Share on other sites More sharing options...
rick harper Posted September 14, 2015 Share Posted September 14, 2015 If 207SH32 is the correct part number, Mack PDC has stock. Price should be about 28 us dollars. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-303820 Share on other sites More sharing options...
Full Floater Posted September 26, 2015 Author Share Posted September 26, 2015 Ok I ordered that kit, waited patiently for it and oh boy....its here!!!!! Is this what im needing? Its a whole LOT of orings!!!! Now im scared..... Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-305188 Share on other sites More sharing options...
Challenger Posted September 26, 2015 Share Posted September 26, 2015 Thats everything. Just mark everything as you take it apart. Maybe take a picture of the direction of the HI/Lo cylinders. What ever makes it easier for you to reassemble. You can use silicone for the gasket. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-305190 Share on other sites More sharing options...
mrsmackpaul Posted September 26, 2015 Share Posted September 26, 2015 dont use to much silicon as it squeezes out on the inside and can drop down and get in between the high low sliding dog then the whole box has to come out maybe lable the air lines as drop them off but if I can change them anyone can LOLPaul 1 Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-305196 Share on other sites More sharing options...
Full Floater Posted September 26, 2015 Author Share Posted September 26, 2015 Should I have the selector in Neutral for disassembly? Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-305206 Share on other sites More sharing options...
Challenger Posted September 27, 2015 Share Posted September 27, 2015 You can remove the top cover in any selection. Once you have the topcover on a bench, the shift cylinders have to be in neutral. But you can move the dogs with your hands or just shoot air into the fittings to put it in neutral. It will make sense when you have it on the bench. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-305306 Share on other sites More sharing options...
Full Floater Posted September 30, 2015 Author Share Posted September 30, 2015 So its the entire top cover that comes off?? then the cylinders can be dismantled? Sorry, dumb question Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-305613 Share on other sites More sharing options...
Challenger Posted September 30, 2015 Share Posted September 30, 2015 So its the entire top cover that comes off?? then the cylinders can be dismantled? Sorry, dumb questionYes, Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-305621 Share on other sites More sharing options...
Full Floater Posted October 14, 2015 Author Share Posted October 14, 2015 Ok so im finally getting around to working on it. Pulled the top cover off no problem, lots of room. I noticed that on the reverse cylinder, the air fitting on the square top cover is loose. I have attached a picture of it. I can wiggle it to the point where it will come right out. Could this have been my issue all along? I understand that this is not the supply line for reverse but still wondering. I could not hear air escaping at any time however. If this is a problem, does anyone have the part number for these fittings? I suppose it may snug up with the line attached; but thought id ask anyways.And I started on the hi-lo cylinder and im REALLY struggling with this internal snap ring. I have attached a picture of it also. I had to leave it for today due to frustration. Are there any tricks for that one? Im feeling like I want to leave the remainder of that cylinder alone as the hi lo was working fine. I have neatly placed all parts that I have removed, in order on a clean table but im not yet seeing all of the o-rings that I got in the kit. They must be down deeper in the hi-lo cylinder im guessing. And am I safe to use brakeclean to clean everything up in there? ...if all the orings are getting replaced that is.. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-307494 Share on other sites More sharing options...
b61mack Posted October 15, 2015 Share Posted October 15, 2015 Can you still get a ReMack top cover for a 1070 10 speed, if so how much. Quote Link to comment https://www.bigmacktrucks.com/topic/41549-seleting-reverse-on-a-12speed/#findComment-307497 Share on other sites More sharing options...
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