Allison Transmission Questions
- Thread starter AllisonMan
- Start date
RE: Allison Transmission Questions
hi
The initiative taken for the concern is very serious and needs an attention of everyone. This is the concern which exists in the society and needs to be eliminated from the society as soon as possible.
Eliza
Car Insurance
hi
The initiative taken for the concern is very serious and needs an attention of everyone. This is the concern which exists in the society and needs to be eliminated from the society as soon as possible.
Eliza
Car Insurance
Triple E
Senior Member
Re: Allison Transmission Questions
db, Ok I got the analog temperature sensor installed. Took the MH out for a 100 mile drive. The highest reading I got was 124 degrees F. Mainly stayed around 116. Outside air temp. at 50. I check the sensor location with my IR and it match the sensor reading. At these low readings is there a problem or am I all right? The book says to be above 170 to measure the fluid level.
Yes, I am on the output to the cooler. ">" Not the input.
db, Ok I got the analog temperature sensor installed. Took the MH out for a 100 mile drive. The highest reading I got was 124 degrees F. Mainly stayed around 116. Outside air temp. at 50. I check the sensor location with my IR and it match the sensor reading. At these low readings is there a problem or am I all right? The book says to be above 170 to measure the fluid level.
Yes, I am on the output to the cooler. ">" Not the input.
dbarton291
Senior Member
Re: Allison Transmission Questions
I'd say you are doing just fine. In my opinion, if the vehicle is able to run that cool, I would set the oil level a little below the hot full mark on the dipstick. That will allow for expansion of the oil if you get into a hot climate, steep hills, or tow a car.
I'd say you are doing just fine. In my opinion, if the vehicle is able to run that cool, I would set the oil level a little below the hot full mark on the dipstick. That will allow for expansion of the oil if you get into a hot climate, steep hills, or tow a car.
RE: Allison Transmission Questions
I have an oil leak problem.
1997 Safari Cat 3126/Allison MD 3060. Started last fall, appears to be getting slightly worse. Leaks at rest (sitting still) as well as down the road. Around 38K miles on the clock. It appears the leak comes from the sump/body gasket. I'm fairly handy and was wondering if this is a DIY project, or will I open a can of worms. Attached link should give a reasonable picture of the leak, 40 miles after cleaning.
Tranny Leak Picture
I have an oil leak problem.
1997 Safari Cat 3126/Allison MD 3060. Started last fall, appears to be getting slightly worse. Leaks at rest (sitting still) as well as down the road. Around 38K miles on the clock. It appears the leak comes from the sump/body gasket. I'm fairly handy and was wondering if this is a DIY project, or will I open a can of worms. Attached link should give a reasonable picture of the leak, 40 miles after cleaning.
Tranny Leak Picture
dbarton291
Senior Member
RE: Allison Transmission Questions
It can be done. What you're looking at on the bottom of the transmission is not a pan. It is the control module assembly. You have to drop the control module using a floor jack because it is heavy. You also have to be careful depending on which connector you have coming out the side of the trans connecting to the chassis wiring harness. I would suggest getting a service manual so you have the torque values for the bolts and the procedures for dealing with the connector. A manual may also come in handy down the road sometime.
It can be done. What you're looking at on the bottom of the transmission is not a pan. It is the control module assembly. You have to drop the control module using a floor jack because it is heavy. You also have to be careful depending on which connector you have coming out the side of the trans connecting to the chassis wiring harness. I would suggest getting a service manual so you have the torque values for the bolts and the procedures for dealing with the connector. A manual may also come in handy down the road sometime.
executive_36
New Member
RE: Allison Transmission Questions
Hi Allison Man!
I also posted this as a new thread because I'm not yet used to using this forum. Here's my situation...
I was driving my 1988 Executive 36' coach with a Cummins 'B' and an Allison AT545 pusher at approx 20mph when it inadvertantly went into reverse and ground to a halt in the middle of the road.
The Transmission will not come out of reverse, but it will simultaneously engage in 1,2,3 and 4 forward gears. Of course, with both a forward and reverse gear engaged, the trans temperature wants to heat up pretty quickly.
Here's my question: Is there anything in the transmission that can cause this problem other than a malfunctioning valve body?
Please provide me with any insight you would like to share with me, thanks so much.
Hi Allison Man!
I also posted this as a new thread because I'm not yet used to using this forum. Here's my situation...
I was driving my 1988 Executive 36' coach with a Cummins 'B' and an Allison AT545 pusher at approx 20mph when it inadvertantly went into reverse and ground to a halt in the middle of the road.
The Transmission will not come out of reverse, but it will simultaneously engage in 1,2,3 and 4 forward gears. Of course, with both a forward and reverse gear engaged, the trans temperature wants to heat up pretty quickly.
Here's my question: Is there anything in the transmission that can cause this problem other than a malfunctioning valve body?
Please provide me with any insight you would like to share with me, thanks so much.
RE: Allison Transmission Questions
Thanks for the reply. I don't see a connector on the control module. There is a a feedthrough harness connector above the nameplate which appears attached to the main body of the transmission - does that pass through to the control module assembly?
Thanks for the reply. I don't see a connector on the control module. There is a a feedthrough harness connector above the nameplate which appears attached to the main body of the transmission - does that pass through to the control module assembly?
dbarton291
Senior Member
RE: Allison Transmission Questions
Yes it does. That's the one I'm referring to.
Yes it does. That's the one I'm referring to.
Triple E
Senior Member
RE: Allison Transmission Questions
This question is for "db". In this picture of the transmission, you will see a bolt head on the side of the module. What is this? Is it a test port? I have looked in my manual and cannot find anything on it. If I wanted to install a pressure sensor, would this be a place to do it and what kind of pressure would I find? Thanks, -Steve
This question is for "db". In this picture of the transmission, you will see a bolt head on the side of the module. What is this? Is it a test port? I have looked in my manual and cannot find anything on it. If I wanted to install a pressure sensor, would this be a place to do it and what kind of pressure would I find? Thanks, -Steve
dbarton291
Senior Member
Re: Allison Transmission Questions
That's a main pressure tap. It's intended for troubleshooting, kinda like taking blood pressure. You could put a pressure gauge in there if you wanted to, but if that gauge or line you hook up leaks going down the road.......you'll have a big mess on your hands. Max pressure on most gauges used to troubleshoot at this location is usually 300 psi.
That's a main pressure tap. It's intended for troubleshooting, kinda like taking blood pressure. You could put a pressure gauge in there if you wanted to, but if that gauge or line you hook up leaks going down the road.......you'll have a big mess on your hands. Max pressure on most gauges used to troubleshoot at this location is usually 300 psi.
RE: Allison Transmission Questions
Hello AllisonMan and others. Recently my HT 755CR tranny began acting up. When I first start up my RV it will shift into drive without a problem but after two or three shifts from drive to neutral or reverse the tranny refuses to engage a gear and stays in neutral. I have to shut the engine down and restart before it will go into gear. I've noticed the shifting has changed also with shifts being later than normal. I have replaced the Throttle Position Sensor on the foot pedal without any success. I've talked with a mechanic and he thinks it might be a computer interface module that some of the older DDEC systems required. Your thoughts and any other comments would be appreciated
Rob
Hello AllisonMan and others. Recently my HT 755CR tranny began acting up. When I first start up my RV it will shift into drive without a problem but after two or three shifts from drive to neutral or reverse the tranny refuses to engage a gear and stays in neutral. I have to shut the engine down and restart before it will go into gear. I've noticed the shifting has changed also with shifts being later than normal. I have replaced the Throttle Position Sensor on the foot pedal without any success. I've talked with a mechanic and he thinks it might be a computer interface module that some of the older DDEC systems required. Your thoughts and any other comments would be appreciated
Rob
dbarton291
Senior Member
RE: Allison Transmission Questions
Need to determine if this coach uses a TPS dedicated to the transmission, or if the transmission gets its throttle position signal from the DDEC engine via TECL - transmission to engine communication link.
Code 21 is throttle position sensor. This code generates with a failed TPS, or if the trans ECU reads the TPS (trans dedicated or TECL) in an error zone, which is on either end of the TPS stroke.
If the vehicles uses a dedicated transmission TPS, it may be misadjusted to the high side (closer to open throttle, or towards the end of the TPS stroke). That will make the shifts occur higher until the TPS autocals, and if the trans sees a high throttle signal in neutral, it will inhibit range.
If the vehicle uses TECL, there is an interface module that was used. That could be defective and may be the problem. With TECL, the TPS you replaced on the foot pedal may be for the engine.
You have a dedicated trans TPS if you have dual potentiometers on the throttle pedal, or you will see the black TPS body with a cable attached to the engine throttle pedal. If the engine is DDEC, most of those did use TECL, but not all.
If you have TECL, my money is on the interface module, or the wiring to it.
If you have a dedicated trans TPS, the most likely cause is misadjustment of the cable or the pot on the throttle pedal. Adjustment of the cable is covered in the Allison operators manual and mechanics' tips booklet for the 755. To adjust a dedicated pot on the throttle pedal, I believe you have to plug in Allison DOC (or an old DDL reader) to read the throttle readings as you turn the pot on its two mounting screws which hold the potentiometer onto the throttle pedal assy.
Sometimes I get a little wordy. I hope this makes sense.
Need to determine if this coach uses a TPS dedicated to the transmission, or if the transmission gets its throttle position signal from the DDEC engine via TECL - transmission to engine communication link.
Code 21 is throttle position sensor. This code generates with a failed TPS, or if the trans ECU reads the TPS (trans dedicated or TECL) in an error zone, which is on either end of the TPS stroke.
If the vehicles uses a dedicated transmission TPS, it may be misadjusted to the high side (closer to open throttle, or towards the end of the TPS stroke). That will make the shifts occur higher until the TPS autocals, and if the trans sees a high throttle signal in neutral, it will inhibit range.
If the vehicle uses TECL, there is an interface module that was used. That could be defective and may be the problem. With TECL, the TPS you replaced on the foot pedal may be for the engine.
You have a dedicated trans TPS if you have dual potentiometers on the throttle pedal, or you will see the black TPS body with a cable attached to the engine throttle pedal. If the engine is DDEC, most of those did use TECL, but not all.
If you have TECL, my money is on the interface module, or the wiring to it.
If you have a dedicated trans TPS, the most likely cause is misadjustment of the cable or the pot on the throttle pedal. Adjustment of the cable is covered in the Allison operators manual and mechanics' tips booklet for the 755. To adjust a dedicated pot on the throttle pedal, I believe you have to plug in Allison DOC (or an old DDL reader) to read the throttle readings as you turn the pot on its two mounting screws which hold the potentiometer onto the throttle pedal assy.
Sometimes I get a little wordy. I hope this makes sense.
dbarton291
Senior Member
RE: Allison Transmission Questions
Allisonman (Ron) is pretty busy these days. I'm not him. I'm just some flunkie that like to answer questions to keep his service skills from fading over time. Maybe it's a losing battle.
Allisonman is like a guy that wears a cape and tights and has a big S on his chest. Think of me as Jimmie Olsen. Gee Willikers.
Allisonman (Ron) is pretty busy these days. I'm not him. I'm just some flunkie that like to answer questions to keep his service skills from fading over time. Maybe it's a losing battle.
Allisonman is like a guy that wears a cape and tights and has a big S on his chest. Think of me as Jimmie Olsen. Gee Willikers.
RE: Allison Transmission Questions
Allisonman it would appear that my tranny problem is solved. After installing a new TECL the problem DID NOT go away so I was left with only two options. Take it back to DD/Allison or investigate a wiring harness problem. You did mention in your post that it could be the wiring. I decided to check it out and when I pulled the tranny ECU and disconnected the J1B and J1A plugs I found a slight bit of moisture and some oxidation in J1B (the plug which has the TPS inputs). I cleaned everything up and finished off with Electrical Contact Cleaner and dielectric grease. These plugs are not water tight so I goopuckied them with some silicon. I now have two new non-returnable electrical components to add to my inventory (TPS and DDEC II ATEC I TECL).Thanks again for all your help
Rob
Allisonman it would appear that my tranny problem is solved. After installing a new TECL the problem DID NOT go away so I was left with only two options. Take it back to DD/Allison or investigate a wiring harness problem. You did mention in your post that it could be the wiring. I decided to check it out and when I pulled the tranny ECU and disconnected the J1B and J1A plugs I found a slight bit of moisture and some oxidation in J1B (the plug which has the TPS inputs). I cleaned everything up and finished off with Electrical Contact Cleaner and dielectric grease. These plugs are not water tight so I goopuckied them with some silicon. I now have two new non-returnable electrical components to add to my inventory (TPS and DDEC II ATEC I TECL).Thanks again for all your help
Rob