GM response to 4l60e shifts
03-27-2009, 08:02 PM
#1
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GM response to 4l60e shifts does this sound fishy to anyone besides me? I have this same exact problem but now I'm frustrated that there's no way to fix it.
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.
this is a bulletin from GM that i found. it is considered a normal condition. i'd still do the preliminary checks to make sure all driveline components are in good condition
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.
this is a bulletin from GM that i found. it is considered a normal condition. i'd still do the preliminary checks to make sure all driveline components are in good condition
03-27-2009, 08:27 PM
#2
Yep I have read that one to and I understand the mechanics of it and yes its in the design of the trans. Your releasing one element while simultainiously engaging another and snothing in between(neutral like) Goal is to get them as close together as possible to avoid the reversal however you cant let them overlap much either or you will prematurley burn or wear the clutch/band elements. So you get the occasional "CLUNK" its harmless other than maybe being a little anoying however.
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03-27-2009, 08:34 PM
#4
The problem is mass production.
If you take the time to set the clutches up right, maybe adjust the feed hole sizes and accumulators you can get rid of the noise.
After doing all this you need to be sure it shifts properly, the 2-3 and 3-2 timing. Band release vs clutch apply.
If you take the time to set the clutches up right, maybe adjust the feed hole sizes and accumulators you can get rid of the noise.
After doing all this you need to be sure it shifts properly, the 2-3 and 3-2 timing. Band release vs clutch apply.
03-27-2009, 08:36 PM
#6
Actually theres no guarantee that would eliminate it. I mean tighter clearances do help some but its not that theres something wrong really its the very design itself that allows it.
Its kinda like pushing something except you can only push on it two foot at a time. Each time you let go it slows breifly "reverses" so theres a jolt when you apply again.
The only real way to eliminate it is to Eliminate all drive train slack but then things would wear on each other to extreme levels and bind up.
Its kinda like pushing something except you can only push on it two foot at a time. Each time you let go it slows breifly "reverses" so theres a jolt when you apply again.
The only real way to eliminate it is to Eliminate all drive train slack but then things would wear on each other to extreme levels and bind up.
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03-27-2009, 08:41 PM
#7
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Actually theres no guarantee that would eliminate it. I mean tighter clearances do help some but its not that theres something wrong really its the very design itself that allows it.
Its kinda like pushing something except you can only push on it two foot at a time. Each time you let go it slows breifly "reverses" so theres a jolt when you apply again.
The only real way to eliminate it is to Eliminate all drive train slack but then things would wear on each other to extreme levels and bind up.
Its kinda like pushing something except you can only push on it two foot at a time. Each time you let go it slows breifly "reverses" so theres a jolt when you apply again.
The only real way to eliminate it is to Eliminate all drive train slack but then things would wear on each other to extreme levels and bind up.
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03-27-2009, 08:57 PM
#8
Like I said you can reduce it by tightening clearances and as mentioned working with hydraulics but to some degree its is there, It cannot be worked out of the trans because its part of its design. The only way to totally for sure eliminate it would be to redesign the trans from scratch and of course eliminate drive train slack completey which would wear it out much faster.
And actually other cars do have it the AOD, AODE, 4R70W FORD units suffer from the downshift drivtrain clunk on the 3-4 and 4-3 shifts the AODE and 4R70W are not as bad due to a design change in lockup style.
But virtually any trans that uses sprags and multi clutch sets will have varying degrees of this feeling.
I will say that NON PERFORMANCE oreinted transmissions tend to do it less because they are allowed to slip and overlap more.
Power handling sacraficed for comfort.
Lincolns , the big caddys, luxury cars .
Now there is a trans called the CVT but thats a whole nother ballgame and from what I hear are not so good performance wise. I think nissan was playing with it for a while I remember there "no shift shock" comercials but I dont see them anymore so not so sure how that worked out for them.
And actually other cars do have it the AOD, AODE, 4R70W FORD units suffer from the downshift drivtrain clunk on the 3-4 and 4-3 shifts the AODE and 4R70W are not as bad due to a design change in lockup style.
But virtually any trans that uses sprags and multi clutch sets will have varying degrees of this feeling.
I will say that NON PERFORMANCE oreinted transmissions tend to do it less because they are allowed to slip and overlap more.
Power handling sacraficed for comfort.
Lincolns , the big caddys, luxury cars .
Now there is a trans called the CVT but thats a whole nother ballgame and from what I hear are not so good performance wise. I think nissan was playing with it for a while I remember there "no shift shock" comercials but I dont see them anymore so not so sure how that worked out for them.
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03-27-2009, 09:09 PM
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my 97 silverado does this. The original owner told me its done it since he drove it off the lot. He had it checked out a couple times and they also told him it was normal. I always thought it was the limited slip though.
03-28-2009, 07:05 AM
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There is a solution.You must make the 3/2 control valve inactive and only use a .118" to .125" orifice to split 3rd clutch oil from its path to the clutch pack to the release side of the servo.I did this with a mod to the valve and a new seperator plate.
