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dandretti
New Member
6 Posts |
 Posted - 04/03/2010 : 09:36:08 AM
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My at545 makes a chirping noise from 1st to 2nd and occasionally a groaning noise from 2nd to 3rd when I have a load ( never over the vehicle GVWR)and it is warmed up. I also have an issue pulling from a dead stop on a slope or incline and even from a level stop. The engine will simply stall at about 1500 RPM at first and barely increase. If I can get it rolling and the engine (1999 cummins 5.9 ecm controlled) gets to about 1800 RPM it will suddenly come to life (trans giving more power to the rear wheels) almost as if a valve or switch turns on. Engine has been checked and is running to spec (checked by a cummins guru at Pape-Kenworth). The shifts points are consistant. I have 4:11 rears. Trans fluid looks good and does not smell burned.
My questions are;
Can there be something keeping the trans from producting enough pressure for off the line torque? Perhaps a sticking valve or ruined TC/pump?
Can a blocked internal filter produce these symptoms by restricting the fluid supply?
I have had these issues since I purchased the rig and the trans only has 30k miles. It was a reman from an outfit in Texas.
Could the reman shop have installed a torque limiting setup for the previous owner to limit wear on the trans?
Thanks in advance!
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wagonmaster
Top Member
USA
2298 Posts |
Posted - 04/05/2010 : 06:12:26 AM
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| Since you haven't told us what type/size unit you have it's pretty hard to judge the issues. It sounds to me like it could be that the Cummins "B" engine is getting well into boost RPM and starting to pull hard at the 1800 RPM you mentioned. The AT545 isn't an electronic transmission and will NOT likely have anything attached to it to limit engine torque. I'm curious as to why you think the transmisson is the limiting factor in this problem..... |
Joe
Land of the Free, because of the Brave! |
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dandretti
New Member
6 Posts |
Posted - 04/05/2010 : 2:48:40 PM
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Thanks for the reply. This is in an f800.
I am not sure what the issue is caused by but I have looked really hard at the engine for the issue and it simply does not make sense. I had some trans speciallists tell me that the at545 will make a chirping noise during shifts when it is not producting enough pressure from the TC/pump. I don't know much about autmatic transmissions but I have a gift for solving most problems quickly. This one has me stumped.
I own and operate heavy equipment and commercial vehicles so I have a feel for when something is not right. I may be asking more of this rig than it can deliver. However, it should reliably and safely handle itself when operated within the specs of the vehicle, which it most definately does not at this point. That being said, I am searching for a little direction on where to look I indeed do have a transmission issue.
I have been reading the forums for awhile and appreciate the comments and knowledge.
I made the comment about the transmission being the limiting factor because it "feels" like something in it is holding the engine back until I can get the truck rolling when it finally acts normal (other than the trans noises).
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International-9.0
Advanced Member
USA
459 Posts |
Posted - 04/05/2010 : 4:52:47 PM
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I may be wrong about your understanding, but I'm going on what I can understand best from your post. I think perhaps you are confusing an automatic transmission with a hydrostatic transmission. The gear/fluid pump in an automatic transmission has nothing to do with the force that drives it. The gear pump is completely separate from the operation of the torque convertor. The pump simply creates pressurized fluid. The pressurized fluid is supplied to the valve body and govenor/modulator assemblies which provides shift control for the transmission. This fluid is used to apply clutches to change gears, which is routed by the valve body.
The rest of the fluid is sent to the torque converter housing, cooled, and used to lubricate the gearsets in the transmission. The only reason there is pressurized fluid going to the TC housing is to keep it cool (and full, it will drain some when the vehicle is off). It leaves the convertor housing and goes to the cooler just as fast as it enters, but the housing itself is not under a great deal of fluid pressure (not from the gear pump anyways).
The TC is a 3 piece deal. There is a driving member, stator, and driven member. The engine rotates one turbine, and this turbine directs fluid pressure onto the driven turbine. This is what creates the force for moving. The fluid is "used", but it is not "pressurized" by the gear pump to create movement.
The stator is in between the two turbines and has a one way clutch. When you are starting with high throttle and low speed, the stator does not turn and there is a very large speed difference between the two turbines. It is designed to redirect fluid flow from one turbine to the next in such a way that the torque provided by the engine is multiplied. The down side of this is a reduction in efficiency and alot of heat that must be dissipated. When you get up to speed and both turbines are running nearly the same speed, the stator will begin to spin with the turbines and efficiency increases as well as heat decreasing.
The only problem I know of in a torque convertor (one without lockup clutch like the 545) is that the one way clutch goes bad on the stator and the vehicle will feel like it's "slipping." If your transmission cooler is plugged or you are getting inadequte fluid from the gear pump, the TC housing my have air in it which would also cause the feeling of excess "slip."
I think the 545 had several different TCs available depending on the engine and torque produced by that engine. It's possible the reman was not paired up correctly for the exact specs of your engine. This would not give you enough "slip" or torque multiplication to get started on a hill.
It wouldn't hurt to change your internal and external trans filters to make sure you have adequate fluid pressure. It's unlikely this is causing the type of problem you describe. Usually lack of fluid causes slipping in the TC or clutches and the transmission will act strangely.
If you have clean filters, correct fluid level, and the correct TC for your rig, then it's possible that your engine is not producing the proper amount of pre-boost torque to get the turbo spinning. The Ford 6.6 I had was set extremely lean on take off and I thought it would never get going from a start. As soon as the boost began to pick up, it would jerk your head back in the seat. I guess this is how they were able to achieve emissions in 50 states with the same engine version. Most had a separate california version. Certain CAT 3116 engines were very bad for not having enough starting torque. Intake or exhaust air leaks, dirty/damaged aftercooler, turbo problems, and fuel system issues are among a few things that will affect low end take off power very easily.
Low take off power is usually a problem with the engine and not the transmission. My only thought is that the TC has too low of a stall speed for that engine. I hope this helps a little bit.
Jonathan |
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dandretti
New Member
6 Posts |
Posted - 04/05/2010 : 6:30:46 PM
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I think I am getting somewhere. Your explanation was GREAT Jonathan! I am suspecting that the reman transmission was set up wrong for my engine. This would explain my not being able to get into the engines powerband until after it gets moving. The cummins 24v in this application is not the low rpm grunt that came in dodge pickups. It likes to run between 2000 and 2600 RPM and is slugish below 1400. The turbo does not start "sounding off" until after I get moving.
These were the three TC's available. Can you tell by the ratio's what the stall speed should be? I have not been able to find that info on googling it.
Type.........................Single-stage, 3-element, multiphase
Stall torque ratio.........TC 230-2.60; TC 275-1.96; TC 290-1.72
I have changed the exterior filter but not the internal one. I will propbably need to replace the trans. Besides the low takoff issue it does make noise during shifts and it will only be a matter of time before things get worst.
From other posts I have read it seems the weakness of the at545 is in controlling internal heat. When I replace it I would like to know what kind of cooler to put on it from day 1.
Again you have been mnost helpfull.
Vince |
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Fastback
Top Member
1500 Posts |
Posted - 04/06/2010 : 07:40:57 AM
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Your AT545/electronic controlled diesel operating description does not sound too far off from the way our AT545/T444Es operate. The AT545 is a pretty light duty automatic that doesn't lock up in any gear, also engine torque output has to be limited to about 540 ft lb.s inorder to not exceed the torque capacity of the tranny.
I am somewhat surprised a F800 would even have this tranny, I would have thought a F700 would be about the limit.
Another thought is the 4.11 gears may make it a bit tough to get your loaded rig rolling, especially if you have 11R22.5 tires. Our AT545 school buses all have 4.44 gears |
Why yes, the ORIGinal CHARGER is a Fastback |
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wagonmaster
Top Member
USA
2298 Posts |
Posted - 04/06/2010 : 10:15:58 AM
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| Excellent Jonathan! Dandretti, the valve body in the AT545 can be programmed for higher shift points by adjusting the springs. It's easier to do by removing the valve body and programming it with the valve body machine that lets you "tailor" the shift points to the specific engine you are using. An Allison dealer can do that for you and the cost should have been included in the overhaul. If not it should be nominal, especially if you take them the valve body. This will allow your engine to get into boost prior to gear changes dropping the RPM and could solve the problem you describe. |
Joe
Land of the Free, because of the Brave! |
Edited by - wagonmaster on 04/06/2010 10:16:32 AM |
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Fastback
Top Member
1500 Posts |
Posted - 04/06/2010 : 11:06:31 AM
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quote:
Originally posted by wagonmaster
Excellent Jonathan! Dandretti, the valve body in the AT545 can be programmed for higher shift points by adjusting the springs. It's easier to do by removing the valve body and programming it with the valve body machine that lets you "tailor" the shift points to the specific engine you are using. An Allison dealer can do that for you and the cost should have been included in the overhaul. If not it should be nominal, especially if you take them the valve body. This will allow your engine to get into boost prior to gear changes dropping the RPM and could solve the problem you describe.
Question; Where did you read that his shift points were too low? |
Why yes, the ORIGinal CHARGER is a Fastback |
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dandretti
New Member
6 Posts |
Posted - 04/06/2010 : 1:42:00 PM
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I am thankful to be learning so much. I know I am not the only one that has run accross this issue but most have probably kept looking at the engine as the issue. I had mine thoroughly tested including pressure test in the IC and computer interface while driving the truck which reported all the perameters in the engine. I really don't have an issue (other than the shifting noises) once I am rolling good. It is when I have any kind of load, maybe 25k and I stop and try to get moving again.
I thank all of you for your great insight and welcome more information as the post continues on.
I am curious as to the difference in the three TC's that are offered for at545. I assume one must be for a gas engine and one is for the cummin's 8.3? Either of these is propbably totally wrong for my application. Does anyone know more about these TC's and why they are different?
Vince |
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Fastback
Top Member
1500 Posts |
Posted - 04/06/2010 : 2:04:38 PM
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quote:
Originally posted by dandretti
I am thankful to be learning so much. I know I am not the only one that has run accross this issue but most have probably kept looking at the engine as the issue. I had mine thoroughly tested including pressure test in the IC and computer interface while driving the truck which reported all the perameters in the engine. I really don't have an issue (other than the shifting noises) once I am rolling good. It is when I have any kind of load, maybe 25k and I stop and try to get moving again.
Is your 25k just the load or does that include the weight of the truck?
That transmission is only rated for maximum total GVW in a school bus at 30k. For an on highway refuse type truck 23,250 lbs. total GVW. and not acceptable for off highway useage in this application. |
Why yes, the ORIGinal CHARGER is a Fastback |
Edited by - Fastback on 04/06/2010 2:47:05 PM |
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International-9.0
Advanced Member
USA
459 Posts |
Posted - 04/06/2010 : 6:48:30 PM
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Dandretti,
I'm not sure on the stall ratios. I've heard of them before, but I never actually understand what the mean or how they are calculated. Can anybody else explain the math on this? I'm sure it isn't too complicated, but I don't know the "stall ratio" is a ratio of (what values are being compared?).
Jonathan |
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dandretti
New Member
6 Posts |
Posted - 04/06/2010 : 7:10:19 PM
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25k is the total weight. The truck is a 26k rated truck. As a little humor, my little chevy pickup has better tug than this horse. You would think a bigger truck is for WORK. I have to laugh at the engineers that make things sometimes.
A vehicle has many factors that make it useable and safe. If you pull up to a light at an intersection on a slight hill and have to stop, it is not safe if you can't move forward through the interesction before the light turns again. I am speaking of a vehicle that is within it's loaded design limits.
I had a chevy 3500hd for about five years some time ago. I pulled a full size 4x4 416 cat backhoe on a 24k pintle trailer for 4 of those years with not one issue, even pulling 8% grades in the high desert of Prescott AZ. It was a stick and had 5;13 gears but it was a toy compared to my f800. (I was always a safe driver and inspected my vehicle and especially the brakes).
I am confident with the knowledge of all of you experts that I will finally be able to put a finger on this problem and not take pot shots at fixing it. Thanks again and I really do appreciate the info comming in.
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Wolf0r
Top Member
USA
2181 Posts |
Posted - 04/20/2010 : 11:32:43 AM
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quote:
Originally posted by wagonmaster
Excellent Jonathan! Dandretti, the valve body in the AT545 can be programmed for higher shift points by adjusting the springs. It's easier to do by removing the valve body and programming it with the valve body machine that lets you "tailor" the shift points to the specific engine you are using. An Allison dealer can do that for you and the cost should have been included in the overhaul. If not it should be nominal, especially if you take them the valve body. This will allow your engine to get into boost prior to gear changes dropping the RPM and could solve the problem you describe.
I had a 545 replaced a few years back in a GMCV that we had bigger tires on 11r225 from 10r225. The trans always shifted weird even before the tire swap. One day it just quit pulling all together and we had it towed to Allison. After a rebuilt was installed the tech told me he made adjustments to the way it shifted. He did a wonderful job because it's still running the route today. |
“The good thing about science is that it's true whether or not you believe in it.”
Neil deGrasse Tyson |
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Harrison Fire
Senior Member
United States
175 Posts |
Posted - 04/25/2010 : 04:56:56 AM
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An inherited 96 IH 3800 needed an Allison so I called Williams with the numbers from the tag. This bus was always a dog. It's a spare and the drivers try to avoid using it because of the slow Giddyup. Before I installed the reman (fresh trans was sitting on the floor) I remembered the low shift points. That triggered my "This Aint Right!" switch. Then called the local IH/Navistar dealer with the bus VIN for the original trans numbers. They didn't match. Traded for the right trans and now it shifts nicely. Perhaps your Ford dealer can run the VIN.
Also a broken flex plate makes interesting noises when shifting before the center tears out.
HF |
My Fleet? (6) 93/99 IH 3800 Thomas and Blue Bird, Hydraulic Brakes, Manual and Auto Trans, (10) 00/06 FS65 Thomas Air Brake and Auto Trans, (2) 06 C2 Thomas and (2) 09/10 IC CE 300, Plus 3 more from another District |
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dandretti
New Member
6 Posts |
Posted - 06/28/2011 : 4:09:16 PM
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| Allas! Problem solved! I had kept telling the shops that I thought it was the computer programming. Sure enough there was a limit set to 1400 rpm until the computer sensed road speed, which seemed to be about 4 mph. That kept the thing from even getting out of its own way until it was moving pretty good. I had the tech look at EVERYTHING in insight that could relate to this symptom, while I was present. It did not take long to find it. I had him set that perameter to 3000 and it takes of great now. So much for Cummin's Northwest and Kenworth in Eugene. They took my money and told me they could not find anything. I should have been a tech! I would love to rub their noses in it. But I am to nice for that. |
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08 Thomas EF
Top Member
533 Posts |
Posted - 06/28/2011 : 8:16:31 PM
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Thanks from an outsider to everyone who posted in this thread, lots of great information!  |
Edited by - 08 Thomas EF on 06/28/2011 8:17:08 PM |
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Topic |
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Allison AT545 making noise, low torque.
