I have a shuddering tranny and the dealer can't repro...

RFCRD · **Posted:** Thu Jul 13, 2006 10:06 am

Joe Romas wrote:

Do those with the shuddery transmission also get a "clunk" type sound when you put it in park :?:

It feels like the transmission has torque applied to it. Kind of like pulling it out of park when your on a hill :cry:

This is a all the time type problem and I may take it in because they can reproduce it. As far as a fix goes I think we can only establish a history of our problems before the warranty expires and wait for them to "get it right" :shock:

I'm affraid they're going to try and fix it with a flash but I think it's going to require a different/better torque converter

Only thing I think a flash will do is to prolong the failures till they're out of warranty

Most electronic diesels will pull heavily againts the torque converter at idle. IIRC the term Detroit Diesel uses is "isychronous idle". This is where the computer meters fuel and adjust timing to maintain a steady engine RPM regardless of the load placed on the engine. This will happen at an idle (or any given RPM) up to the torque peak until the engine stalls. Once torque converter oil pressures are built the vehicle will want to move. Create resistance (holding the brake) and the engine computer will adjust to counter the resistance. Take it out of gear and you relieve this torque load (clunk). This is very common to OTR buses with a Detroit Diesel/Allison combination. It takes significant effort to hold them back when stopped at long lights and have even seen the parking brakes fail to hold when left idling and in gear. This is also one of the reasons your cruise control maintains very stable speed.

dog_party · **Posted:** Thu Jul 13, 2006 12:54 pm

That shudder was listed as "normal operation" by my "service" center. They won't even send a tech to ride with me. It happens to me after WOT acceleration followed closely by a throttle lift to (at least) half throttle. I resolved the issue by not lifting off the throttle. The next time I get pulled over, I'm going to claim that doing 98MPH is "normal operation," because Doctor Z told me that I can't drive at half-throttle.

RFCRD wrote:

Most electronic diesels will pull heavily againts the torque converter at idle. IIRC the term Detroit Diesel uses is "isychronous idle". This is where the computer meters fuel and adjust timing to maintain a steady engine RPM regardless of the load placed on the engine. This will happen at an idle (or any given RPM) up to the torque peak until the engine stalls. Once torque converter oil pressures are built the vehicle will want to move. Create resistance (holding the brake) and the engine computer will adjust to counter the resistance. Take it out of gear and you relieve this torque load (clunk). This is very common to OTR buses with a Detroit Diesel/Allison combination. It takes significant effort to hold them back when stopped at long lights and have even seen the parking brakes fail to hold when left idling and in gear. This is also one of the reasons your cruise control maintains very stable speed.

That's good info, 'cause I was wondering the same thing. Sucker sounds like I hit a steel door with a ball-peen hammer when I shift into Park in the parking garage I park in during the day.

TDI4BY · **Joined:** Sun Apr 02, 2006 11:56 pm **Posts:** 644

Joe Romas wrote:

Do those with the shuddery transmission also get a "clunk" type sound when you put it in park :?:

It feels like the transmission has torque applied to it. Kind of like pulling it out of park when your on a hill :cry:

This is a all the time type problem and I may take it in because they can reproduce it. As far as a fix goes I think we can only establish a history of our problems before the warranty expires and wait for them to "get it right" :shock:

I'm affraid they're going to try and fix it with a flash but I think it's going to require a different/better torque converter

Only thing I think a flash will do is to prolong the failures till they're out of warranty

What you are feeling/hearing is SO normal. Don't worry about it.

RFCRD · **Posted:** Thu Jul 13, 2006 11:12 pm

dog_party wrote:

That shudder was listed as "normal operation" by my "service" center. They won't even send a tech to ride with me. It happens to me after WOT acceleration followed closely by a throttle lift to (at least) half throttle. I resolved the issue by not lifting off the throttle. The next time I get pulled over, I'm going to claim that doing 98MPH is "normal operation," because Doctor Z told me that I can't drive at half-throttle.

RFCRD wrote:

Most electronic diesels will pull heavily againts the torque converter at idle. IIRC the term Detroit Diesel uses is "isychronous idle". This is where the computer meters fuel and adjust timing to maintain a steady engine RPM regardless of the load placed on the engine. This will happen at an idle (or any given RPM) up to the torque peak until the engine stalls. Once torque converter oil pressures are built the vehicle will want to move. Create resistance (holding the brake) and the engine computer will adjust to counter the resistance. Take it out of gear and you relieve this torque load (clunk). This is very common to OTR buses with a Detroit Diesel/Allison combination. It takes significant effort to hold them back when stopped at long lights and have even seen the parking brakes fail to hold when left idling and in gear. This is also one of the reasons your cruise control maintains very stable speed.

That's good info, 'cause I was wondering the same thing. Sucker sounds like I hit a steel door with a ball-peen hammer when I shift into Park in the parking garage I park in during the day.

You should see one of those buses shifting into neutral. Will hear a loud "pop/screech" and rocks the body, can sometimes see the rear axle shift or hop slightly.

I did notice mine shifting from forward to reverse and back again without the sloppy lag time since the filter TSB was done a few days ago.

I have a shuddering tranny and the dealer can't repro...

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