90plow Posted August 2, 2020 Share Posted August 2, 2020 I have an eaton8ll in my 2007 Mack granite I recently purchased. Truck has 212,000 miles and 20,000 hours. Trans seems fine other than the 5th to 4th drop. Occasionally the trans misses 4th and seems to be in 8th. It’s driving me nuts when I’m downshifting loaded. Some have said the synchros are shot and have suggested just getting a rebuilt trans for 3800 and throwing it in the truck vs. re doing the synchros. Could it be anything besides synchros? How intense is the synchro replacement? thanks Eric Quote Link to comment Share on other sites More sharing options...
Macktech20 Posted August 2, 2020 Share Posted August 2, 2020 (edited) It depends if you need a clutch usually what I would do if the truck doesn't need a clutch I would just unbolt the back box and just do synchros without having to pull the transmission. It is way easier to do synchros on a Mack compared to a fuller if you're doing it in frame. Fuller's run helical cut gears and makes it a little bit more of a pain in the ass to get the gears to mesh back together when you're going back together. If you do plan on doing the synchros in the truck you shouldn't have to worry about the countershafts falling on you like with a Mack transmission if you dont have the retaining plate in. Because everything comes out with the back box on a fuller. Edited August 2, 2020 by Macktech20 Quote Link to comment Share on other sites More sharing options...
Truck Shop Posted August 2, 2020 Share Posted August 2, 2020 It's a synchronizer hub in the back section, and yes you do have to remove the counter shaft bearing covers and install retaining straps to hold the counter shafts in-place It is much easier to just remove the transmission, stand vertical on bell, install straps on counter shafts and remove the rear section. It's easier to reinstall plus easier to check/reset counter shaft end play.. Quote One ping only Link to comment Share on other sites More sharing options...
blackdog2 Posted August 2, 2020 Share Posted August 2, 2020 Problem with 7th gear jumping out and cant hold it in since new 2001-RD dealer told me poppet spring -balls 3rd time out of warranty now they put bearing kit sliding clutch and fork still jumps out on the way home from dealer in Hartford Conn.....park it in the corner and buy older MACK's late 80's.... Quote Ed Link to comment Share on other sites More sharing options...
tjc transport Posted August 2, 2020 Share Posted August 2, 2020 all but one of the 8ll trans trucks i ever drove had this problem. i think the 8ll is the absolute worst trans ever made. 10, 13, 15 and 18 speeds never had that issue. 1 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment Share on other sites More sharing options...
90plow Posted August 2, 2020 Author Share Posted August 2, 2020 21 minutes ago, tjc transport said: all but one of the 8ll trans trucks i ever drove had this problem. i think the 8ll is the absolute worst trans ever made. 10, 13, 15 and 18 speeds never had that issue. I have one in my single axle and it’s a nice trans. Can’t be the worst trans ever made if it’s in thousands of trucks without major issues. Quote Link to comment Share on other sites More sharing options...
tjc transport Posted August 2, 2020 Share Posted August 2, 2020 every one i have ever seen or know that has one always has issues with 3-7 jumping out of gear. my granite was so bad after the third trans we put an 18 speed in it. 1 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment Share on other sites More sharing options...
JoeH Posted August 2, 2020 Share Posted August 2, 2020 (edited) When I downshift mine from 3rd/7th sometimes it stays in gear, even though I have the shifter in neutral??? Stays in til I punch the clutch so it doesn't explode... PoS... And it'll sneak out of 7th if you're coasting with light throttle. My trucking application would do much better with a Mack 10 speed, multi reverse. Let's go David, chime in on how wrong I am. Edited August 2, 2020 by JoeH 1 Quote Link to comment Share on other sites More sharing options...
theakerstwo Posted August 3, 2020 Share Posted August 3, 2020 1 hour ago, JoeH said: When I downshift mine from 3rd/7th sometimes it stays in gear, even though I have the shifter in neutral??? Stays in til I punch the clutch so it doesn't explode... PoS... And it'll sneak out of 7th if you're coasting with light throttle. My trucking application would do much better with a Mack 10 speed, multi reverse. Let's go David, chime in on how wrong I am. You have a broken snap ring or thrust washer on the main shaft. Quote glenn akers Link to comment Share on other sites More sharing options...
JoeH Posted August 3, 2020 Share Posted August 3, 2020 2 minutes ago, theakerstwo said: You have a broken snap ring or thrust washer on the main shaft. How about when trying to come out of first for an upshift and the shifter snags halfway out of gear and ruins your shift to 2nd, having to go back to first to get momentum going again? Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted August 3, 2020 Share Posted August 3, 2020 6 hours ago, tjc transport said: all but one of the 8ll trans trucks i ever drove had this problem. i think the 8ll is the absolute worst trans ever made. 10, 13, 15 and 18 speeds never had that issue. I need to put my wallet in Wild Dave’s mouth so he doesn’t pitch a fit and bite his tongue off when he reads this thread. 1 1 Quote Link to comment Share on other sites More sharing options...
theakerstwo Posted August 3, 2020 Share Posted August 3, 2020 45 minutes ago, JoeH said: How about when trying to come out of first for an upshift and the shifter snags halfway out of gear and ruins your shift to 2nd, having to go back to first to get momentum going again? The trans needs to come out and open it up and you will see the problems.With it staying in gear you should be able to get in in another gear at same time.It will not move and you will bend the counter shafts and twist the main shaft. 2 Quote glenn akers Link to comment Share on other sites More sharing options...
Truck Shop Posted August 3, 2020 Share Posted August 3, 2020 (edited) Main shaft end play, rear main shaft support bearing or input shaft bearing allowing 3rd and 4th sliding clutch to move, does the shift lever move fore and aft when throttling up or down while moving. Plus 3rd and 4th gear clutching teeth are probably worn right along with the sliding clutch teeth. 3rd and 7th are used alot and first to go. Plus a worn broken main shaft key can cause issues too. Edited August 3, 2020 by Truck Shop Quote One ping only Link to comment Share on other sites More sharing options...
90plow Posted August 3, 2020 Author Share Posted August 3, 2020 13 minutes ago, Truck Shop said: Main shaft end play, rear main shaft support bearing or input shaft bearing allowing 3rd and 4th sliding clutch to move, does the shift lever move fore and aft when throttling up or down while moving. Plus 3rd and 4th gear clutching teeth are probably worn right along with the sliding clutch teeth. 3rd and 7th are used alot and first to go. Plus a worn broken main shaft key can cause issues too. Are you referring to my issue or the other guy who hijacked the thread with a different topic? Quote Link to comment Share on other sites More sharing options...
JoeH Posted August 3, 2020 Share Posted August 3, 2020 20 hours ago, 90plow said: I have an eaton8ll in my 2007 Mack granite I recently purchased. Truck has 212,000 miles and 20,000 hours. Trans seems fine other than the 5th to 4th drop. Occasionally the trans misses 4th and seems to be in 8th. It’s driving me nuts when I’m downshifting loaded. Some have said the synchros are shot and have suggested just getting a rebuilt trans for 3800 and throwing it in the truck vs. re doing the synchros. Could it be anything besides synchros? How intense is the synchro replacement? thanks Eric Do you have any air leaks that sound like they're coming from the trans? Could be a fault with your "combination cylinder" sticking or not getting enough air pressure to move it from high to low on the range shift. My truck has 262k miles and 20,300+ hours, and sounds like mine has broken pieces inside, yours could be in similar shape with the synchros. Quote Link to comment Share on other sites More sharing options...
JoeH Posted August 4, 2020 Share Posted August 4, 2020 On 8/2/2020 at 11:01 AM, 90plow said: I have an eaton8ll in my 2007 Mack granite I recently purchased. Truck has 212,000 miles and 20,000 hours. Trans seems fine other than the 5th to 4th drop. Occasionally the trans misses 4th and seems to be in 8th. It’s driving me nuts when I’m downshifting loaded. Some have said the synchros are shot and have suggested just getting a rebuilt trans for 3800 and throwing it in the truck vs. re doing the synchros. Could it be anything besides synchros? How intense is the synchro replacement? thanks Eric https://www.eaton.com/content/dam/eaton/products/transmissions/vehicle-transmissions/8ll/eaton-fuller-havey-duty-transmissions-service-manual-trsm1500-en-us.pdf Snoop through the table of contents "in vehicle service procedures". Looks like auxiliary section (page 118) can be removed and services in chassis. Then jump to bench procedure section to see how to do rebuild. Quote Link to comment Share on other sites More sharing options...
doubleclutchinweasel Posted August 4, 2020 Share Posted August 4, 2020 (edited) Been following this one more for my info than for any other reason. Sounds like it got a little off-track! What JoeH said seems to make sense. Sounds like the hi-lo range shift isn't happening. Probably should look at the air valves and cylinders first. If the cylinder is moving but the fork isn't that might point to the fork moving on the rod. But it looks like that woul happen all the time, not just sometimes. Incidentally, I did pull the rear (auxiliary) section off a 15-speed while still in the truck to replace the hi-lo synchro assembly. It would downshift, but it would grind. On that one, I had to shift it between hi and lo several times when first starting up before taking off, just to get the hi-lo shift working. Afterwards, it would shift all day without trouble. But, if I started up in the morning, took off and shifted to hi, it would not go in the first time or two. Probably needed a slave valve. Not sure if the 8LL is the same setup. Oh, and that range shift slave valve only opened when the transmission was in neutral. So, there might be something preventing it from doing so. Be interested to hear what you finally find. Edited August 4, 2020 by doubleclutchinweasel Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment Share on other sites More sharing options...
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