4T45E automatic transaxle clank/lurch upon engine start
09-03-2007, 06:17 PM
#1
Senior Member
Thread Starter
Join Date: 05-26-2007
Location: ...
Posts: 1,554
4T45E automatic transaxle clank/lurch upon engine start
Okay, this is an intermittent thing on my '07. It only does it occasionally, so i want to try and get a handle on what could be causing it, before I take it to dealer, because they might not be able to duplicate it since it only happens once in a while. It doesn't feel right at all when it does it. What happens is sometimes when you start the car, immediately (within first second after starting) after the engine starts there is a noticeable "clank" sound from within the transaxle (automatic transaxle) and sometimes its enough that you can feel the car lurch slightly. This is when the shifter is locked in "PARK", but it will also do it with the shifter in "NEUTRAL." Also, it is more prone to do it when the car is parked on a slight uphill incline. Case in point: it is more likely to do it if I start it up while parked in our driveway which has a slight uphill grade, than if I start it in our garage which is pretty level. It only lasts about a second. It feels and sounds exactly like the trans is trying to shift itself momentarily into gear for a second then changes its mind. I would also describe it as more intense when it happens if the car is parked in the driveway, i.e. slight uphill grade-- more likely to feel the car lurch slightly, than if it was one of the occurrences on level parking surface such as in the garage.
The shifter moves and works as normal, there are no looseness or slack issues with it. The trans operates and shifts normally, there is no sticking in any gear and no problem shifting into or out of PARK or NEUTRAL. Best way to describe it is that the trans glitches and tries to shift itself momentarily then aborts the action. Only just after the engine starts, within about a second of engine lighting off.
But it doesn't do it all the time. I hate intermittent issues.
The shifter moves and works as normal, there are no looseness or slack issues with it. The trans operates and shifts normally, there is no sticking in any gear and no problem shifting into or out of PARK or NEUTRAL. Best way to describe it is that the trans glitches and tries to shift itself momentarily then aborts the action. Only just after the engine starts, within about a second of engine lighting off.
But it doesn't do it all the time. I hate intermittent issues.
09-03-2007, 11:18 PM
#2
Senior Member
Join Date: 08-17-2006
Location: Ottawa, Ontario
Posts: 1,851
I get that clank sound, but only when I move it from park to reverse after the car has sat for a bit.
I can also get the cloank sound to happen sometimes (but not all the time) when driving and move it from D to I. I've had it into the dealer once so far and they could not reproduce the clank sound.
When I was rotating my tires, I noted that there is a fair amount of forward and backwards movement with the rotors. I've been thinking maybe the clank sound is the hub moving and making contact with the rotor.
Going to take it in again before it gets cold to get this checked out again.
I can also get the cloank sound to happen sometimes (but not all the time) when driving and move it from D to I. I've had it into the dealer once so far and they could not reproduce the clank sound.
When I was rotating my tires, I noted that there is a fair amount of forward and backwards movement with the rotors. I've been thinking maybe the clank sound is the hub moving and making contact with the rotor.
Going to take it in again before it gets cold to get this checked out again.
09-04-2007, 06:29 AM
#3
Senior Member
Join Date: 08-18-2006
Location: Hatboro, PA
Posts: 1,036
I also have the intermittent lurch problem. I have an '06 auto with 10,000 mi. on it. It hasn't been getting any worse and I haven't taken it in yet because I don't want to waste my time to be told they can't reproduce it.
09-04-2007, 12:27 PM
#4
Senior Member
Thread Starter
Join Date: 05-26-2007
Location: ...
Posts: 1,554
Agreed. Exactly why I want to find out what is causing it first, before taking it in.
Black Rose, it is the same sound as when shifting, its a shifting "clank" noise but it happens right at start-up without ever touching the shifter. When it happens, that is. Very intermittent. Seems like a momentary attempt (about one second long or less) by the trans to engage a gear then it aborts.
If checking the fluid level on these units wasn't such a pain in the butt it would be the first thing my old-school self would do. But to check the fluid in the 4T45E you need to:
1. Lift the car, taking care to keep it level, probably require four certified jackstands. Could also park it over a mechanic's pit, or use a bonafide lift.
2. Taking necessary pre-cautions, start the car and let it idle for 3-5 minutes. Fluid must be at least 104F but not full operating temp either.
3. Leaving the engine running, remove the check bolt on passenger side of transaxle. Car must be running or else you'll dump a lot of fluid.
4. If fluid exits the hole where the bolt was, but just barely dribbles out, your fluid level is correct-- replace the bolt.
5. If more than a dribble comes out, the transaxle was overfull. When it stops or slows to a dribble, replace bolt. Fluid level is now correct.
6. If no fluid comes out, it may be low. Remove fill cap. Add fluid .25 qt increments until it starts to drain from check bolt hole. This should be done quickly, or else the fluid will exceed the temperature range and then you have to let it cool and start the process over.
7. After setting the fluid level, replace check bolt and fill cap.
Black Rose, it is the same sound as when shifting, its a shifting "clank" noise but it happens right at start-up without ever touching the shifter. When it happens, that is. Very intermittent. Seems like a momentary attempt (about one second long or less) by the trans to engage a gear then it aborts.
If checking the fluid level on these units wasn't such a pain in the butt it would be the first thing my old-school self would do. But to check the fluid in the 4T45E you need to:
1. Lift the car, taking care to keep it level, probably require four certified jackstands. Could also park it over a mechanic's pit, or use a bonafide lift.
2. Taking necessary pre-cautions, start the car and let it idle for 3-5 minutes. Fluid must be at least 104F but not full operating temp either.
3. Leaving the engine running, remove the check bolt on passenger side of transaxle. Car must be running or else you'll dump a lot of fluid.
4. If fluid exits the hole where the bolt was, but just barely dribbles out, your fluid level is correct-- replace the bolt.
5. If more than a dribble comes out, the transaxle was overfull. When it stops or slows to a dribble, replace bolt. Fluid level is now correct.
6. If no fluid comes out, it may be low. Remove fill cap. Add fluid .25 qt increments until it starts to drain from check bolt hole. This should be done quickly, or else the fluid will exceed the temperature range and then you have to let it cool and start the process over.
7. After setting the fluid level, replace check bolt and fill cap.
09-04-2007, 12:35 PM
#5
Senior Member
Thread Starter
Join Date: 05-26-2007
Location: ...
Posts: 1,554
I would add that due to the 4T45E being a sealed unit, there should be no reason to suspect fluid level being off unless there is a leak.
P.S. Can anyone with access to alldata.com see if there might be a TSB out for this?
P.S. Can anyone with access to alldata.com see if there might be a TSB out for this?
09-04-2007, 02:28 PM
#6
Senior Member
Join Date: 11-10-2006
Location: Montana
Posts: 163
Lone Ranger I found this:
Subject: Slight Vehicle Movement In Park At Start Up After Cold Soak - keywords 3T40 4L60 4L60E 4L65E 4L80E 4L85E 4T40E 4T45E 4T60 4T60E 4T65E 4T80E 5L40E 5L50E 6L50 6L80 6L90 6T70 6T75 AF225 AF235 aisan #PIP3763A - (01/05/2007)
Models: 2007 and Prior Passenger Cars and Light Duty Trucks
Equipped with Automatic Transmission
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some vehicles may rock or move slightly forward or rearward while in park at start up after cold soak. This condition may be accompanied by a clunk noise. This is a slight movement that is more often seen visually, rather than felt, when viewed from the outside and using the auto-start feature, if equipped.
Recommendation/Instructions:
This slight movement is due to the residual transmission fluid in the clutch packs that creates a partial apply on start up. This movement is stopped by the parking pawl and/or transmission fluid exhausting completely from the clutch packs.
This slight movement has no adverse affects on the transmission and no repair should be attempted. This condition is normal. This can be verified by comparing with another identically built vehicle under the same cold conditions.
To prevent this condition from occurring, the parking brake should be utilized as per Owner's Manual recommendations anytime the vehicle is parked.
Subject: Slight Vehicle Movement In Park At Start Up After Cold Soak - keywords 3T40 4L60 4L60E 4L65E 4L80E 4L85E 4T40E 4T45E 4T60 4T60E 4T65E 4T80E 5L40E 5L50E 6L50 6L80 6L90 6T70 6T75 AF225 AF235 aisan #PIP3763A - (01/05/2007)
Models: 2007 and Prior Passenger Cars and Light Duty Trucks
Equipped with Automatic Transmission
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some vehicles may rock or move slightly forward or rearward while in park at start up after cold soak. This condition may be accompanied by a clunk noise. This is a slight movement that is more often seen visually, rather than felt, when viewed from the outside and using the auto-start feature, if equipped.
Recommendation/Instructions:
This slight movement is due to the residual transmission fluid in the clutch packs that creates a partial apply on start up. This movement is stopped by the parking pawl and/or transmission fluid exhausting completely from the clutch packs.
This slight movement has no adverse affects on the transmission and no repair should be attempted. This condition is normal. This can be verified by comparing with another identically built vehicle under the same cold conditions.
To prevent this condition from occurring, the parking brake should be utilized as per Owner's Manual recommendations anytime the vehicle is parked.
09-04-2007, 03:11 PM
#7
Senior Member
Join Date: 08-17-2006
Location: Ottawa, Ontario
Posts: 1,851
I use the parking brake all the time and get the clunk when I take the parking brake off (with my foot on the brake pedal) and move the transmission from P to D.
If I have my foot off the brake pedal when I release the parking brake and then engage the transmission, I usually don't get the clank.
09-04-2007, 04:03 PM
#8
Senior Member
Thread Starter
Join Date: 05-26-2007
Location: ...
Posts: 1,554
GuitHHR, that TSB seems to sum up my issue. Guess its nothing to be concerned with as they state it should be considered a normal condition. Although mine does it sometimes on warm start-up, say starting after sitting parked an hour or so. Thank you for posting it.
09-04-2007, 05:50 PM
#9
Senior Member
Join Date: 11-10-2006
Location: Montana
Posts: 163
No problem, you might just want to keep an eye on it for any more changes or whatnot. Also you might want to document it with your service department. That way if there is something wrong with it and the tranny dies after its out of warranty you can say that you were having problems with it. But don't tell them you are just there to document. If they give you the same bulitin I did tell them its doing it when its hot too. Just my thoughts on it. I know that there have been plenty of times a customer had a problem that we were not able to duplicate and when it problem got to where it was diagnosable after warranty had expired they at least got some help from GM if not repaired free. Then again you have plenty of time on that powertrain warranty.