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Slow shifts 03 Chevy S10 ZR2 4x4 4.3L 4l60e 139k mi

12K views 19 replies 5 participants last post by  tnsmith10 
#1 · (Edited)
I just bought this truck a couple of weeks ago and have changed all fluids (motor oil, tranfer case, front diff, rear diff, ect) except for the transmission. I wanted to get some advice from you experts on this issue before I pull the pan.
At light throttle it shifts fine through all gears (but a little too smooth and long for me since I don't like the clutch disc sacrifice involved with slow/smooth shifts).
But at about 1/2 throttle the 1-2 shift is really slow. It seems like the normal slow/smooth shift you would expect from the factory but then it still has no definite feel of engagement for another ~1/4 second. It's like the first delay of time is being used to fill the accumulator, then more time for the apply piston to close the clearance in clutch pack.
3-4 shift is also really slow at 1/2 throttle.
Converter lock speed seems about normal (too slow for me of course).
I get the same issues at WOT but I've only tried that once because I don't wont to do any major clutch disc damage until I get this issue resolved.
My question is what is the best way to limit this shift delay time - short of a rebuild (I'd hate to go into a fully funtioning tranny when I can get another several thousand miles out of it if I treat it right)? I really can't afford a rebuild but...

BTW, the 4l60e I built for my Trans Am in 2005 with directions on here from Crosley in this thread is still alive and barking tires after several 1/4 mile passes and several thousand road miles. Thanks Crosley!!!
 
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#2 ·
How much have you drive this vehicle? I believe the ecm learns your driving habits and adjusts shift points for maximum performance. You may need to drive out for a little while to let the ecm learn your driving habits. Has the fluid and filter ever been changed? I would change out anyways and throw a can of sea foam in there after you change it.
 
#3 ·
I belive this issue is more extreme than what the block learn in the PCM would adjust for. I'm currently checking to see if I can obtain the same type of PCM editing software for this truck that I use on my 96 4l60e. If so I can probably minimize the clutch disc damage, but I believe that would only be masking the symptoms of a problem that exist in the hard parts/hydraulic circuit.
So, I still plan to purchase software to edit the PCM controls, but not as a preliminary fix for this issue.
The truck has indications of frequent maintenance (with the last service tag <3k miles), although I don't know about tranny service. The fluid has minimal discoloration and has no burnt smell.
Sea Foam is good stuff and has it's place, but I'd like to get to the heart of my issues rather than treating the symptoms on this one. :)
Thanks for your reply crussell85. :)
 
#6 ·
joshp83 said:
a corvette servo would help but that requires to remove the x member and y pipe on a s10 you could also remove the pan take off the epc soleniod turn the allen screw a half a turn clock wise that will firm up your shifts
I failed to see any difference in the servo in my 96 Trans Am WS6 vs Corvette servo. Does it really make much diffence in shift time or is it just intended for better apply force?
I may adjust the pressure control if I need to but I guess I need to get a pressure reading prior to doing so.
Gee, I'm working strictly on industrial machinery these days (nothing automotive) and will need to come up with the test equipment for this transmission that I lost in a fire a couple of years ago. I'll see what I can find tommorrow to check pressures with.
Thanks joshp83! I'll post back when I find the testing equipment.
 
#7 ·
thats because all lt1s already had a corvette servo actually all 93 up f bodys had them the 700r4s are more agressive than the 4l60e with them but idt offers more clamping force and quicker shifts the servo alone will make it firmer but not harsh a 4.3 s10 with a 700r willl bark 2nd hard with a vette servo 4.3 4l60 will not
 
#10 ·
crussell85 said:
Maybe check your local trans shop for parts, you may be able to get them cheaper than the auto parts. Would a shift kit help? Or can you do everything through the ecm that a shift kit would do?
Yes I'd prefer a shift kit to start with, then I can make minor adjustments to the PCM.
Any suggestions for the best kit to purchase for my 4x4 application (I'm running 32x11.50x15 BF Goodrich mud tires so I'm certainly not looking to bark the tires on pavement), I just want firmer shifts than stock in order to save the clutch disc.
 
#12 ·
mike 96 ws6 said:
I just bought this truck a couple of weeks ago and have changed all fluids (motor oil, tranfer case, front diff, rear diff, ect) except for the transmission. I wanted to get some advice from you experts on this issue before I pull the pan.
At light throttle it shifts fine through all gears (but a little too smooth and long for me since I don't like the clutch disc sacrifice involved with slow/smooth shifts).
But at about 1/2 throttle the 1-2 shift is really slow. It seems like the normal slow/smooth shift you would expect from the factory but then it still has no definite feel of engagement for another ~1/4 second. It's like the first delay of time is being used to fill the accumulator, then more time for the apply piston to close the clearance in clutch pack.
3-4 shift is also really slow at 1/2 throttle.
Converter lock speed seems about normal (too slow for me of course).
I get the same issues at WOT but I've only tried that once because I don't wont to do any major clutch disc damage until I get this issue resolved.
My question is what is the best way to limit this shift delay time - short of a rebuild (I'd hate to go into a fully funtioning tranny when I can get another several thousand miles out of it if I treat it right)? I really can't afford a rebuild but...

BTW, the 4l60e I built for my Trans Am in 2005 with directions on here from Crosley in this thread is still alive and barking tires after several 1/4 mile passes and several thousand road miles. Thanks Crosley!!!
with what youre explaining here, the first thing id do is hook up a pressure gauge to see if the trans is getting line rise (pressure should go up when stepping on the gas).
also, id check it for codes with a scan tool and not just a code reader. something that will also pull stored codes.
depending on the answers to these questions will tell whether its worth it or not to go on with any service and/or repairs to the trans.
as far as if the epc solenoid is bad or not and the trans is not getting main line pressure rise, id check to see if the tps is good or not because its possible that the tps is not sending the proper signal for the pcm to control line pressure in the trans.
as far as the suggestion on turning the epc solenoid screw in, i would never turn it in more than 1/8th turn as more than that and main line pressure being too high can be hard on tcc apply and can pull the lining off of inside of the converter. there are other proper ways to fix sloppy shifts.
 
#13 ·
tnsmith10 said:
with what youre explaining here, the first thing id do is hook up a pressure gauge to see if the trans is getting line rise (pressure should go up when stepping on the gas).
Okay, first I need a gauge set-up so let me try to find where to order that from. (got a suggestion / link?).


also, id check it for codes with a scan tool and not just a code reader. something that will also pull stored codes.
depending on the answers to these questions will tell whether its worth it or not to go on with any service and/or repairs to the trans.
I'm trying to work out some issues now with the programming/scanner software supplier to work with my specific vehicle before I spend $450. If I can't resolve this issue quick then I'll take it to a shop with a scanner and post the results.

as far as if the epc solenoid is bad or not and the trans is not getting main line pressure rise, id check to see if the tps is good or not because its possible that the tps is not sending the proper signal for the pcm to control line pressure in the trans.
as far as the suggestion on turning the epc solenoid screw in, i would never turn it in more than 1/8th turn as more than that and main line pressure being too high can be hard on tcc apply and can pull the lining off of inside of the converter. there are other proper ways to fix sloppy shifts.
Thanks! I agree with knowing what pressures exist before I go adjusting anything. I'll get the information for TPS voltage from the scanner data stream readings and post the results. We'll go from there.

Thanks tnsmith10! I've found your directions to be very helpful in the past so I'll do my part to follow what you suggest.
 
#15 ·
First thing I would do is hook up a scanner. Check two specific things: 1) trans temp, and 2) MLP... the shifter position switch.

In the internal wiring harness is a temp sensor. Sometimes you'll pull up the data on a scanner and it says -40 degrees. If its reading something that is nonsense, it needs to be replaced.

The MLP is a relatively common failure. If the ECM doesn't know what gear you've selected, its flying blind.

If both of those check out fine, pull the pan and tell us what kind of debris is in there.

... and I will assume that the speedo is working? Same thing happens with the speedo sensor as the MLP - the ECM doesn't have the proper information to make shift commands.
 
#16 ·
curtis73 said:
First thing I would do is hook up a scanner. Check two specific things: 1) trans temp, and 2) MLP... the shifter position switch.

In the internal wiring harness is a temp sensor. Sometimes you'll pull up the data on a scanner and it says -40 degrees. If its reading something that is nonsense, it needs to be replaced.

The MLP is a relatively common failure. If the ECM doesn't know what gear you've selected, its flying blind.

If both of those check out fine, pull the pan and tell us what kind of debris is in there.

... and I will assume that the speedo is working? Same thing happens with the speedo sensor as the MLP - the ECM doesn't have the proper information to make shift commands.
Okay, I got the issue resolved with the software provider and will finalize the purchase tommorrow, but I'll have to wait a couple of days for shipping (I can receive the software electronically, but I'm going to need a different interface cable than the one I have for my TA, and that will come Fed Ex).
The software includes a fully funtional scanner so I'll be able to provide any information we need.

Yes the speedometer is working.

Thanks curtis73! :)
 
#17 ·
tnsmith10 said:
with what youre explaining here, the first thing id do is hook up a pressure gauge to see if the trans is getting line rise (pressure should go up when stepping on the gas).
also, id check it for codes with a scan tool and not just a code reader. something that will also pull stored codes.
depending on the answers to these questions will tell whether its worth it or not to go on with any service and/or repairs to the trans.
Sorry for the delay posting back. I had some higher priority issues to deal with like thrown rod ect.
The pressure is ~60 psi at idle in park and jumps to ~90 psi at idle in reverse. It drops back to ~60psi at idle in drive and increases as the throttle is increased. When driving at speed the pressure increases with throttle increase and is highest at lower RPM's during acceleration. The highest pressure I observed was ~120 psi.
With my scanner set to transmission mode, current MIL's are: P0420 and P0128.
History MIL's in transmission mode are: P0420, P0128, C0222, B0036, U1016, U1041, U1096, and U1064. (Other than P0420 and P0128, those codes are Supplemental Inflatable Restraint.
 
#18 ·
curtis73 said:
First thing I would do is hook up a scanner. Check two specific things: 1) trans temp, and 2) MLP... the shifter position switch.

In the internal wiring harness is a temp sensor. Sometimes you'll pull up the data on a scanner and it says -40 degrees. If its reading something that is nonsense, it needs to be replaced.

The MLP is a relatively common failure. If the ECM doesn't know what gear you've selected, its flying blind.

If both of those check out fine, pull the pan and tell us what kind of debris is in there.

... and I will assume that the speedo is working? Same thing happens with the speedo sensor as the MLP - the ECM doesn't have the proper information to make shift commands.
According to my scanner the transmission temp sensor is working. On one occasion after a 5 mile 55 MPH drive, the temp was ~180 degrees farenheit.
The scanner displays the correct gear when shifting 1-4. When stopped it displays 1 no matter what position the shifter is in (meaning that the scanner is diplaying the actual gear the transmission is in rather than what position the gear selector lever is in.)
I pulled the pan to change the filter and found absolutely no debris such as metal or friction material in it, although a filter change may have been done recently. If so it wasn't real recent because there was some build-up of dirt, road grime ect on the pan bolt heads.
Yes the speedometer is working fine.
 
#20 ·
mike 96 ws6 said:
Sorry for the delay posting back. I had some higher priority issues to deal with like thrown rod ect.
The pressure is ~60 psi at idle in park and jumps to ~90 psi at idle in reverse. It drops back to ~60psi at idle in drive and increases as the throttle is increased. When driving at speed the pressure increases with throttle increase and is highest at lower RPM's during acceleration. The highest pressure I observed was ~120 psi.
With my scanner set to transmission mode, current MIL's are: P0420 and P0128.
History MIL's in transmission mode are: P0420, P0128, C0222, B0036, U1016, U1041, U1096, and U1064. (Other than P0420 and P0128, those codes are Supplemental Inflatable Restraint.

line pressure is a bit low from what i see. this could explain your shift issue.
from here, i would turn up the epc maybe the 1/8th turn max i mentioned before, or get a new epc.
you should see about 75 lbs in drive at idle.
if you decide to replace it, i recommend a borg warner replacement
 
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