boyle908 Report post Posted April 22, 2011 09 Neptune 35SBD RR4R chassis, Allison 2500MH, Cummins ISB340 11K miles My transmission was stuttering and bogging down on acceleration. This was intermittent and did not seem to have a discernible pattern or set of conditions that caused it. I had it checked and was informed that with the engine braking switch turned on, it was causing the tranny to perform as described above. This was under low gear (1st & 2nd) acceleration only. I have not found anywhere in the transmission/owners manual any documentation that implies or corroborates this happening. The coach is currently in for an REK install and I have not had a chance to verify this yet (no issues with the switch in the "off" position). Has anyone experienced this situation or do you have any information on it? Michael B Share this post Link to post Share on other sites
hermanmullins Report post Posted April 22, 2011 Michael, There could be different causes depending on your Auxiliary Brake System. Is it an Exhaust Brake or a Jake Brake? One affects the exhaust and the other affects the valves. If it is an exhaust brake it may be sticking. However if it is a Jake Brake it could be in the electrical system. You need a service tech to look at it. I may have my terms wrong but you get my meaning. Share this post Link to post Share on other sites
Guest BillAdams Report post Posted April 22, 2011 If you turn the switch off, does the problem go away? Share this post Link to post Share on other sites
boyle908 Report post Posted April 22, 2011 If you turn the switch off does the problem go away? Yes, although I have yet to drive and verify. Share this post Link to post Share on other sites
Guest BillAdams Report post Posted April 22, 2011 Yes, but you don't know if that's correct or not. Let us know after you drive it. Share this post Link to post Share on other sites
boyle908 Report post Posted May 9, 2011 Yes, but you don't know if that's correct or not. Let us know after you drive it. Finally got to check it out. It happens regardless of switch position. Share this post Link to post Share on other sites
Guest BillAdams Report post Posted May 9, 2011 If the switch position does not matter, then their statement that the engine brake being turned on was causing your transmission problems is incorrect -- unless the switch itself is defective and the engine brake never turns off. In general, your engine brake should have no interaction with your transmission performance (especially during acceleration), so I find their comments to be suspect, anyway. Share this post Link to post Share on other sites
boyle908 Report post Posted May 9, 2011 (edited) If the switch position does not matter then their statement that the engine brake being turned on was causing your transmission problems is incorrect unless the switch itself is defective and the engine brake never turns off. In general, your engine brake should have no interaction with your transmission performance (especially during acceleration) so I find their comments to be suspect anyway. I agree with you about their comments. I am concerned about finding someone locally (San Jose area)who can actually & intelligently diagnose and repair. I have been researching and have some thought as to what it could be, Change solenoid, the inhibitor/limiter device that stops it from doing damage to itself or possibly engine fuel filter/s although I did not notice any sluggishness on the engine but it seems feasible. The transmission should not move @ all if there is something wrong according to the what I have read the controller should stop it from moving. Forgot to add that it could be a throttle position sensor issue Still working on it! Thanks for your help Michael Boyle Edited May 10, 2011 by boyle908 Share this post Link to post Share on other sites
rossboyer Report post Posted May 9, 2011 Thank you for letting us know the real cause of the problem. Share this post Link to post Share on other sites
boyle908 Report post Posted June 15, 2011 My final resolution did not post for some reason. I took the unit to FJM trucking in San Jose and within 2-3hrs they found the issue. The primary fuel filter was the issue. On my 09 Neptune/RoadmasterRR4R/Cummins340/Allison 2500 it was located in the hydraulic leveler pump compartment. On the opposite side of the engine to the secondary fuel filter, I had assumed that is was a filter for the hydraulic system (silly assumption) My only excuse is that it had hydraulic lines all around it and even today it looks like part of the HYD system. They replaced the filter and all is well. Michael Boyle Share this post Link to post Share on other sites
