sully66 Posted September 24, 2008 Share Posted September 24, 2008 Does anyone have any tips as to what would cause the hi lo selector in an 85 model R686 T2060 transmission to stick in either hi or low and then go to neutral occasionally and not want to engage in either hi or low. I have pulled apart the air selector on the gear shift and it does everything ok as far as I can work out as far as supplying air each direction and venting it as required.I went to a Mack shop here in OZ and looked at transmissions and the 6 speed one they had had a different top plate on it to the one in my truck. The top plate looks like a 9 speed set up. This has me totally perplexed as I want to order parts but dont want to get the wrong ones as the truck is working in outback australia and I dont want it out of action.Sully Quote Link to comment Share on other sites More sharing options...
Maxville Truck Posted September 24, 2008 Share Posted September 24, 2008 Is this the long or short back box? If you have the long rear box then you have a plain "tin" cover on the rear box with the shift cylinder sticking out the rear top of the rear box.... parallel with the drive shaft. the short rear box has the shift cylinder built into the underside of the top cover. My guess is you have the long rear box with the neutral shift out air switch in the cab. for a multispeed rear PTO. what " may" be going on is it is hanging in the neutral position because of bad o rings or corrosion in the air shift cylinder. Quote Link to comment Share on other sites More sharing options...
sully66 Posted September 24, 2008 Author Share Posted September 24, 2008 Thanks Maxville,Knowing there are a short and long rear box helps.Mine is a short rear box as the shift cylinder must be built into the top cover as the 2 air lines go into the top cover and there are no cylinders etc on the rear of the box.I saw a 6 speed at the Mack shop and it had a cylinder on the rear of the box which mine doesn't have.So would all of the shift cylinders integrated to the top cover have the same parts or are they all different from box to box?ThanksSully Quote Link to comment Share on other sites More sharing options...
Maxville Truck Posted September 25, 2008 Share Posted September 25, 2008 I don't know for sure... however I do know that their has been some updated shift cylinder "kits" for those transmissions, If you give your Vin to your local Mack dealer they should be able to determine if your cylinder could be upgraded, That back cover is pretty easy to remove and put back on.. and pretty easy to repair. just orings inside. we had one get sticky pulled it off took it apart it had rust , I guess from system moisture.. the rust had accumulated, and tore the orings up, I cleaned it up nice, installed new orings and a little grease, Problem solved. Quote Link to comment Share on other sites More sharing options...
sully66 Posted September 25, 2008 Author Share Posted September 25, 2008 Excellent Maxville, The picture explains it all.I can now go to the Mack shop with a bit more information and get the right bits.Thanks for your help.CheersSully Quote Link to comment Share on other sites More sharing options...
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