2-3 pre shift
10-10-2005, 02:16 PM
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2-3 pre shift
I'm a newbeee here and hopefully someone can give me some insight/advice.
02-GMC 1500 4x4 5.3 auto 33k miles. 4.10 gears with 315/75/16's
Only after the truck is warmed up....
Only when the trans shift lever is in 3rd (lever not in OD)....
And Only right before (1/2 - 1 second) before the trans shifts from 2nd to 3rd I feel a clunk...thud.
It feels like as if the TC is locking up right before the 2nd to 3rd shift harder than it should and thats what I'm feeling. I'm not even sure if the TC is supossed to lock up at this time / condition.
I took it to the stealership. I told them what I said above AND said I wasnt sure if its sliping and catching or what.
The Trans Tech test drove and logged the data as he drove. The data showed nothing abnormal. He says he didnt feel anything.
The service manager test drove and says he didnt feel anything.
I told them the trans has to be fully warmed up and for them to drive it around.... it was ok to do so.
Between the 2 test drives they only put 9.3 miles on my truck (averaged 4.5 miles per test drive) so I'm not convince they even had the trans fluid fully warmed up yet.
I went a head and had them change the trans fluid and filter.
Any one have any input at all? Any questions?
Any input is appreciated.
Thanks in advance
---dane
02-GMC 1500 4x4 5.3 auto 33k miles. 4.10 gears with 315/75/16's
Only after the truck is warmed up....
Only when the trans shift lever is in 3rd (lever not in OD)....
And Only right before (1/2 - 1 second) before the trans shifts from 2nd to 3rd I feel a clunk...thud.
It feels like as if the TC is locking up right before the 2nd to 3rd shift harder than it should and thats what I'm feeling. I'm not even sure if the TC is supossed to lock up at this time / condition.
I took it to the stealership. I told them what I said above AND said I wasnt sure if its sliping and catching or what.
The Trans Tech test drove and logged the data as he drove. The data showed nothing abnormal. He says he didnt feel anything.
The service manager test drove and says he didnt feel anything.
I told them the trans has to be fully warmed up and for them to drive it around.... it was ok to do so.
Between the 2 test drives they only put 9.3 miles on my truck (averaged 4.5 miles per test drive) so I'm not convince they even had the trans fluid fully warmed up yet.
I went a head and had them change the trans fluid and filter.
Any one have any input at all? Any questions?
Any input is appreciated.
Thanks in advance
---dane
10-10-2005, 02:32 PM
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i have this problem also with 6000 miles on the clock some say it's normal, but i just got used to it. Try to get them to drive around again with 10 miles and let us know what they say.
10-10-2005, 05:22 PM
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Thanks for the reply.
I just had to pick uyp my daughter and it was doing it. Since the Dealer is right there I stopped in and had the service manager take a ride with me.
He felt it this time but didnt latst time. I told him because he only drove 4-5 miles.
Now he is going to talk to the techs and I have to call back to see what he says and schedule another appointment.
I just had to pick uyp my daughter and it was doing it. Since the Dealer is right there I stopped in and had the service manager take a ride with me.
He felt it this time but didnt latst time. I told him because he only drove 4-5 miles.
Now he is going to talk to the techs and I have to call back to see what he says and schedule another appointment.
10-15-2005, 03:38 PM
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A/T - 2-3 Upshift or 3-2 Downshift Clunk Explanation
File In Section: 07 - Transmission/Transaxle
Bulletin No.: 01-07-30-042A
Date: December, 2002
INFORMATION
Subject:
Information on 2-3 Upshift or 3-2 Downshift Clunk Noise
Models:
2003 and Prior Light Duty Trucks
with 4L60E or 4L65E Automatic Transmission (RPOs M30, M32)
This bulletin is being revised to add the 2003 model year as well as information about 3-2 downshift Please discard Corporate Bulletin Number 01-07-30-042 (Section 07 - Transmission/Transaxle).
Some vehicles may exhibit a clunk noise that can be heard on a 2-3 upshift or a 3-2 downshift.
During a 2-3 upshift, the 2-4 band is released and the 3-4 clutch is applied. The timing of this shift can cause a momentary torque reversal of the output shaft that results in a clunk noise. This same torque reversal can also occur on a 3-2 downshift when the 3-4 clutch is released and the 2-4 band applied. This condition may be worse on a 4-wheel drive vehicle due to the additional tolerances in the transfer case.
This is a normal condition. No repairs should be attempted.
According to GM this is normal just anoying there is a nickel plated yolk that will fix it but not worth it.
File In Section: 07 - Transmission/Transaxle
Bulletin No.: 01-07-30-042A
Date: December, 2002
INFORMATION
Subject:
Information on 2-3 Upshift or 3-2 Downshift Clunk Noise
Models:
2003 and Prior Light Duty Trucks
with 4L60E or 4L65E Automatic Transmission (RPOs M30, M32)
This bulletin is being revised to add the 2003 model year as well as information about 3-2 downshift Please discard Corporate Bulletin Number 01-07-30-042 (Section 07 - Transmission/Transaxle).
Some vehicles may exhibit a clunk noise that can be heard on a 2-3 upshift or a 3-2 downshift.
During a 2-3 upshift, the 2-4 band is released and the 3-4 clutch is applied. The timing of this shift can cause a momentary torque reversal of the output shaft that results in a clunk noise. This same torque reversal can also occur on a 3-2 downshift when the 3-4 clutch is released and the 2-4 band applied. This condition may be worse on a 4-wheel drive vehicle due to the additional tolerances in the transfer case.
This is a normal condition. No repairs should be attempted.
According to GM this is normal just anoying there is a nickel plated yolk that will fix it but not worth it.
10-16-2005, 11:22 AM
#6
The TSB explains how the noises are made, but in your case there's more.
The reason you don't have problems in "D" is because the overrun clutches in "D" are not engaged. Any reverse torque can simply overrun the engine.
With the selector in "3" the overrun clutches are engaged and the clunk is heard.
If it really bothers you the 3-4 apply clutch time can be decreased to reduce the overlap. Enlarge the feed orifice in the separator plate for the 3-4 clutch. It is the small hole in those designated #27 in an ATSG manual. This will also reduce the slight lunge forward you are probably feeling right now during this shift.
The reason you don't have problems in "D" is because the overrun clutches in "D" are not engaged. Any reverse torque can simply overrun the engine.
With the selector in "3" the overrun clutches are engaged and the clunk is heard.
If it really bothers you the 3-4 apply clutch time can be decreased to reduce the overlap. Enlarge the feed orifice in the separator plate for the 3-4 clutch. It is the small hole in those designated #27 in an ATSG manual. This will also reduce the slight lunge forward you are probably feeling right now during this shift.
10-20-2005, 01:26 PM
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Originally Posted by James B.
The TSB explains how the noises are made, but in your case there's more.
The reason you don't have problems in "D" is because the overrun clutches in "D" are not engaged. Any reverse torque can simply overrun the engine.
With the selector in "3" the overrun clutches are engaged and the clunk is heard.
If it really bothers you the 3-4 apply clutch time can be decreased to reduce the overlap. Enlarge the feed orifice in the separator plate for the 3-4 clutch. It is the small hole in those designated #27 in an ATSG manual. This will also reduce the slight lunge forward you are probably feeling right now during this shift.
The reason you don't have problems in "D" is because the overrun clutches in "D" are not engaged. Any reverse torque can simply overrun the engine.
With the selector in "3" the overrun clutches are engaged and the clunk is heard.
If it really bothers you the 3-4 apply clutch time can be decreased to reduce the overlap. Enlarge the feed orifice in the separator plate for the 3-4 clutch. It is the small hole in those designated #27 in an ATSG manual. This will also reduce the slight lunge forward you are probably feeling right now during this shift.
I love you James !!!!!
Actually, I didnt put in the "slight lunge forward" info that you did as sometimes I feel it and sometimes I dont. I tried to explain it as a "slight burst of speed" on another forum but your description is perfect.
Also, just to clarify, I'm feeling this (not really hearing it) right BEFORE I feel the trans start its shifting from 2 to 3. Probably a 1/2 to 3/4 of a second before I feel the shift starting. I realize that the trans probably starts its shifting process before I can ever feel it.
Does this still sound like the same thing? I think so.. for example. The trans computer starts its Torque Management process before the mechanical shift actualy starts. During this, the reverse torque (using your words that seem to make sense) built up in the drive train kinda "bumps" back into the trans thus causing the feeling. Does that sound right knowing that I dont know transmission very well?
James, what really bothers me most is the fact I dont know what it is and I dont know if it is hurting the trans or if it is just a non-detrimental characteristic.
Do you have any input as to the affects this has on the trans?
Thank you very much for your input.... are yours too 5.3AlmnBlk and everyone.
PS James, this is James B from Fullsizechevy too right? I havent seen you there in a long time. You are very knowledgable. I posted there 1st hoping you would see it !!!
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10-20-2005, 08:51 PM
#8
I'm the same James as on FullSizeChevy. I still read posts in that forum, but less often than here.
What's going on with your transmission is not hurting it if it's as subtle as you describe. All transmissions based on the old 700R4 (4L60-E, 4L65-E, 4L70-E, etc.) will have some overlap or flare to a degree on the 2-3 shift. During the shift the band has to let go as the 3-4 clutch engages. If the band lets go too soon the engine will rev up slightly during the shift because you will experience a moment of first gear. If this happens the engine will not be spinning fast enough for torque to move rearward. If the overrun clutches are applied (as they would be in "3") then during this instant of first gear torque will transfer from the wheels to the engine instead of the other way. That is the "torque reversal" the TSB refers to. It can be loud because all the slop in the drivetrain will move the opposite rotational direction.
If the 3-4 clutches were engaging too soon it would feel like a moment of fourth gear. When this happens the engine will feel like it's bogging during the shift.
The easiest thing to do would be to install a shift kit. Making the shifts quicker and more precise reduces what you are feeling.
-James B.
What's going on with your transmission is not hurting it if it's as subtle as you describe. All transmissions based on the old 700R4 (4L60-E, 4L65-E, 4L70-E, etc.) will have some overlap or flare to a degree on the 2-3 shift. During the shift the band has to let go as the 3-4 clutch engages. If the band lets go too soon the engine will rev up slightly during the shift because you will experience a moment of first gear. If this happens the engine will not be spinning fast enough for torque to move rearward. If the overrun clutches are applied (as they would be in "3") then during this instant of first gear torque will transfer from the wheels to the engine instead of the other way. That is the "torque reversal" the TSB refers to. It can be loud because all the slop in the drivetrain will move the opposite rotational direction.
If the 3-4 clutches were engaging too soon it would feel like a moment of fourth gear. When this happens the engine will feel like it's bogging during the shift.
The easiest thing to do would be to install a shift kit. Making the shifts quicker and more precise reduces what you are feeling.
-James B.
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