kuhar69 Posted July 20, 2010 Share Posted July 20, 2010 I dont know if Im seeing things but I think my cab looks like it's sagging a little????. Is this possible??? another words when Im looking at the truck I sware the cab is sagging down towards the fuel tanks,The weather is hot here in CT so I might be working to hard tell me this is not a bent frame or something??!! Quote Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/ Share on other sites More sharing options...
Rob Posted July 20, 2010 Share Posted July 20, 2010 I dont know if Im seeing things but I think my cab looks like it's sagging a little????. Is this possible??? another words when Im looking at the truck I sware the cab is sagging down towards the fuel tanks,The weather is hot here in CT so I might be working to hard tell me this is not a bent frame or something??!!If you have an air ride cab you may have a leveling valve gone bad, or air bags not being inflated properly. If not an air ride cab, it is possible the insulators have flattened out from age/usage and just need replaced. Cab sagging in older trucks is quite common.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59954 Share on other sites More sharing options...
kuhar69 Posted July 20, 2010 Author Share Posted July 20, 2010 Ok so this is happening im not nuts. I dont have an air ride cab so I will have to check the mounts they must be rubber right??? Quote Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59955 Share on other sites More sharing options...
Rob Posted July 20, 2010 Share Posted July 20, 2010 Ok so this is happening im not nuts. I dont have an air ride cab so I will have to check the mounts they must be rubber right???Yes, they are rubber and compress from the "hammering" they take during normal operation. Ask for a photocopy of how much torque to place upon the retention bolts for proper "squish" when the rubber parts are installed. Too tight and they split, too loose and they do not offer the slight cushioning effect they are for. The cab will really bounce and jerk if they are loose. You want a slight bowing out of the sides of the rubber when tightened properly. I'd say about 3/8ths of an inch would be enough.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59957 Share on other sites More sharing options...
bobo Posted July 20, 2010 Share Posted July 20, 2010 Ok so this is happening im not nuts. I dont have an air ride cab so I will have to check the mounts they must be rubber right??? Your cab should be air ride in 03, they didnt come solid mount bobo Quote Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59958 Share on other sites More sharing options...
kuhar69 Posted July 20, 2010 Author Share Posted July 20, 2010 Yes, they are rubber and compress from the "hammering" they take during normal operation. Ask for a photocopy of how much torque to place upon the retention bolts for proper "squish" when the rubber parts are installed. Too tight and they split, too loose and they do not offer the slight cushioning effect they are for. The cab will really bounce and jerk if they are loose. You want a slight bowing out of the sides of the rubber when tightened properly. I'd say about 3/8ths of an inch would be enough.RobOk very good it sounds like an easy repair and it wont brake the bank at the same time. How long should that take to replace 2 or is there 4?? Quote Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59959 Share on other sites More sharing options...
kuhar69 Posted July 20, 2010 Author Share Posted July 20, 2010 Ok BObo so i might have an air ride cab??. This is my 1st Mack so Im still learning!! My other truck is a kenworth.How do i know if my cab is airride? Quote Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59961 Share on other sites More sharing options...
Rob Posted July 20, 2010 Share Posted July 20, 2010 Ok very good it sounds like an easy repair and it wont brake the bank at the same time. How long should that take to replace 2 or is there 4??There are both lower, and upper mounting rubbers, (bisquits) and all four need to be replaced for both rear cab mounting isolators. Sometimes the bolts and hardware can be reused but I've always used everything new. Mack offers a complete replacement kit. You should be able to change everything out within a couple of hours depending on items that interfere with easy access. Not really a big job to do with minimal tools.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59962 Share on other sites More sharing options...
kuhar69 Posted July 20, 2010 Author Share Posted July 20, 2010 Bobo seems to think i might have an air ride cab on my truck???.I might be having an air issuie that might be related to the sagging cab if you look at my other post under engines Im being told that the cab may be pinching a airline that is restricting my boost??? Quote Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59965 Share on other sites More sharing options...
bobo Posted July 20, 2010 Share Posted July 20, 2010 Ok BObo so i might have an air ride cab??. This is my 1st Mack so Im still learning!! My other truck is a kenworth.How do i know if my cab is airride?Im guessing it has a dump box on it? at the center of cab, at the rear, there will be two air bags and a leveling valve/rod. Check to see the the rubber ends havent broken/rotted off the leveling rod end, or holes in air bag or in air line. use a block of wood and a 2x4 wedged under the cab, where the exhaust mount cross tube runs parrell with the cab. this will give you enough room to look and get you hands under the cab bobo Quote Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59966 Share on other sites More sharing options...
rhasler Posted July 20, 2010 Share Posted July 20, 2010 Ok BObo so i might have an air ride cab??. This is my 1st Mack so Im still learning!! My other truck is a kenworth.How do i know if my cab is airride?There will be two air bags (item 45 in the attachment) in the center of the rear cab mount brace (item 69 in the attachment). The front cab mounts are a split rubber design with a clamp plate on the bottom (items 33 and 75 in the attachment). You definitely have air ride on your cab. Make sure to check the cab shocks too.2003 RB688S Cab Mounting.pdf Quote "Mebbe I'm too ugly and stupid to give up!" Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59968 Share on other sites More sharing options...
kuhar69 Posted July 20, 2010 Author Share Posted July 20, 2010 ok rhasler I printed the page you provided for me thank you so much very helpful. Tommrow I will take a look at the truck.You guys are a huge help this is what makes this country great.By the way what is your name???Mark Quote Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-59971 Share on other sites More sharing options...
kuhar69 Posted August 24, 2010 Author Share Posted August 24, 2010 Rhsler I had a bad linkage to the leveling valve the cab is ok now that was easy!!.Now If I could have a chance to fix my no pulling power.Mark Quote Link to comment https://www.bigmacktrucks.com/topic/14914-2003-rb688s-cab-sagging-down/#findComment-62218 Share on other sites More sharing options...
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