LT1 4 speed auto
Thread Starter
Staging Lane
Joined: Feb 2019
Posts: 94
Likes: 4
LT1 4 speed auto Got a 1994 Firebird with an LT1. For some reason it does not want to take off in first gear. I can manually shift it to second and it will take off from there, but it feels like it’s skipping bad in first. Upon further investigation, it seems like it’s not slipping. It’s in third gear. Once moving, by taking off in second then putting it in drive, it up shifts perfect but won’t downshift and won’t go back down to first when stopped.
the transmission was rebuilt one year ago.
Could this be something simple? Like a vacuum hose, plug, or electronics?
the transmission was rebuilt one year ago.
Could this be something simple? Like a vacuum hose, plug, or electronics?
TECH Junkie
Joined: Jun 2008
Posts: 3,202
Likes: 1,390
From: Nitro Alley
It seems that you are uncertain with how the Transmission is operating...
or NOT operating properly.
So, I would recommend first trying to look at the PCM data for the 4L60E Transmission.
1994 however uses the GM specific OBD1 Data System...
and may be more difficult for you to find a Shop/ Business that can read the Data for you.
or NOT operating properly.
So, I would recommend first trying to look at the PCM data for the 4L60E Transmission.
1994 however uses the GM specific OBD1 Data System...
and may be more difficult for you to find a Shop/ Business that can read the Data for you.
Thread Starter
Staging Lane
Joined: Feb 2019
Posts: 94
Likes: 4
It seems that you are uncertain with how the Transmission is operating...
or NOT operating properly.
So, I would recommend first trying to look at the PCM data for the 4L60E Transmission.
1994 however uses the GM specific OBD1 Data System...
and may be more difficult for you to find a Shop/ Business that can read the Data for you.
or NOT operating properly.
So, I would recommend first trying to look at the PCM data for the 4L60E Transmission.
1994 however uses the GM specific OBD1 Data System...
and may be more difficult for you to find a Shop/ Business that can read the Data for you.
per a YouTube video… the guy described my exact symptoms and said it was the solenoids.
What are your thoughts on shift solenoids
TECH Junkie
Joined: Jun 2008
Posts: 3,202
Likes: 1,390
From: Nitro Alley
Do you know how many miles are on the Valve-Body?
I would be concerned that the AFL Valve-Train may be worn...
Low AFL pressure can cause: "what I think you are trying to say is happening".
Do you know if the AFL Valve has ever been replaced?
Has the Valve-Body ever been Vacuum-Tested?
I would be concerned that the AFL Valve-Train may be worn...
Low AFL pressure can cause: "what I think you are trying to say is happening".
Do you know if the AFL Valve has ever been replaced?
Has the Valve-Body ever been Vacuum-Tested?
Thread Starter
Staging Lane
Joined: Feb 2019
Posts: 94
Likes: 4
Do you know how many miles are on the Valve-Body?
I would be concerned that the AFL Valve-Train may be worn...
Low AFL pressure can cause: "what I think you are trying to say is happening".
Do you know if the AFL Valve has ever been replaced?
Has the Valve-Body ever been Vacuum-Tested?
I would be concerned that the AFL Valve-Train may be worn...
Low AFL pressure can cause: "what I think you are trying to say is happening".
Do you know if the AFL Valve has ever been replaced?
Has the Valve-Body ever been Vacuum-Tested?
I don’t know if any of that has been done. The transmission was rebuilt 2 months ago. The previous owner has it done. The shop won’t honor me the warranty. Besides, that shop is over an hour away.
there is a local transmission guy that is reputable near me.
here is where I’m stuck. I can take it to a reputable shop known for specializing in GM cars, particularly this era, or the local reputable transmission guy. I’m worried that trans guy will just say it’s a bad rebuild or just swap out solenoids and not fix the problem. I also worried the regular mechanic will just say it’s a bad ECM or transmission without really digging.
Thread Starter
Staging Lane
Joined: Feb 2019
Posts: 94
Likes: 4
With regards to this thread…..
https://ls1tech.com/forums/automatic...e-problem.html
I’m 100% experiencing symptoms 11 and 12. It’s intermittent. Goes back and forth from what 11 describes and 12. Maybe this helps.
https://ls1tech.com/forums/automatic...e-problem.html
I’m 100% experiencing symptoms 11 and 12. It’s intermittent. Goes back and forth from what 11 describes and 12. Maybe this helps.
Thread Starter
Staging Lane
Joined: Feb 2019
Posts: 94
Likes: 4
Solved! Took the car to a local reputable GM mechanic. Scanned it and got code for a bad B solenoid.
he changed both A and B and all is perfect.
the issue is that this transmission has been rebuild two months ago. I called the transmission shop that did the rebuild and he said that they replace all solenoids and he did not know what caused the bad solenoid. He said it could be a bad ignition switch. That was replaced 2 months ago as well.
hopefully this will not be a reoccurring issue.
Any underlying issues that cause premature solenoid failure? Line pressure issue maybe?
he changed both A and B and all is perfect.
the issue is that this transmission has been rebuild two months ago. I called the transmission shop that did the rebuild and he said that they replace all solenoids and he did not know what caused the bad solenoid. He said it could be a bad ignition switch. That was replaced 2 months ago as well.
hopefully this will not be a reoccurring issue.
Any underlying issues that cause premature solenoid failure? Line pressure issue maybe?
Trending Topics
TECH Junkie
Joined: Jun 2008
Posts: 3,202
Likes: 1,390
From: Nitro Alley
That is good news!
Parts like Shift Solenoids can unfortunately stop working at anytime.
This is a big part of why people were reluctant to have electronically operated Engines and Transmissions, when they started being available as options for automobiles.
I have had parts like Shift Solenoids and other electric/ electronic parts be bad in the box just after purchase...
as well as dying a few days later without warning.
Most of the Name Brand parts will have a 12 Month Warranty.
Parts like Shift Solenoids can unfortunately stop working at anytime.
This is a big part of why people were reluctant to have electronically operated Engines and Transmissions, when they started being available as options for automobiles.
I have had parts like Shift Solenoids and other electric/ electronic parts be bad in the box just after purchase...
as well as dying a few days later without warning.
Most of the Name Brand parts will have a 12 Month Warranty.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Joined: Nov 2003
Posts: 6,216
Likes: 236
From: Wichita KS / Rancho San Diego
Parts like Shift Solenoids can unfortunately stop working at anytime.
This is a big part of why people were reluctant to have electronically operated Engines and Transmissions, when they started being available as options for automobiles.I have had parts like Shift Solenoids and other electric/ electronic parts be bad in the box just after purchase...as well as dying a few days later without warning.
This is a big part of why people were reluctant to have electronically operated Engines and Transmissions, when they started being available as options for automobiles.I have had parts like Shift Solenoids and other electric/ electronic parts be bad in the box just after purchase...as well as dying a few days later without warning.
Dana tried to convince me to go vacuum when we did my first converter and shift kit, but I decided against it - for reasons I don't really remember. But comparing my old school TH400, it feels like there is a more variable and graduated shift timing per throttle input as opposed to the calculated electronic shift timing - if that even makes sense.
TECH Junkie
Joined: Jun 2008
Posts: 3,202
Likes: 1,390
From: Nitro Alley
This is why some of the pro's were advocating vacuum modulation for these trannies back in the day. You don't hear that being advocated much anymore.
Dana tried to convince me to go vacuum when we did my first converter and shift kit, but I decided against it - for reasons I don't really remember. But comparing my old school TH400, it feels like there is a more variable and graduated shift timing per throttle input as opposed to the calculated electronic shift timing - if that even makes sense.
Dana tried to convince me to go vacuum when we did my first converter and shift kit, but I decided against it - for reasons I don't really remember. But comparing my old school TH400, it feels like there is a more variable and graduated shift timing per throttle input as opposed to the calculated electronic shift timing - if that even makes sense.
At this time, the PCM/ Processor was unable to process the monitored input-data quickly enough... (such as the TPS and RPM data)...
and unable to control the EPC Solenoid quickly enough to properly control the Line-Pressure when abrupt pressure changes were needed.
What it ultimately came down to, was that the technology of that era could not do its job quickly enough...
While GM Executives demanded that the Hydra-Matic Engineers produce a result, that current technology could not provide.
This was a bad time for the guys on the 4L60E Team... Many excellent Engineers became fed-up with GM (and quit) over the Early 4L60E.
When Computer processing Technology finally advanced; the PCM was able to process the monitored input data, and control the EPC Solenoid quickly enough to properly control Line-Pressure.
The Vacuum Modulator solution was now no longer needed.
I remember talking to Dana about this... we even discussed it again as recently as 12 to 18 Months ago.
He likes to reminisce a lot.
TECH Regular
Joined: Jan 2013
Posts: 463
Likes: 179
At this time, the PCM/ Processor was unable to process the monitored input-data quickly enough... (such as the TPS and RPM data)...
and unable to control the EPC Solenoid quickly enough to properly control the Line-Pressure when abrupt pressure changes were needed.
What it ultimately came down to, was that the technology of that era could not do its job quickly enough...
and unable to control the EPC Solenoid quickly enough to properly control the Line-Pressure when abrupt pressure changes were needed.
What it ultimately came down to, was that the technology of that era could not do its job quickly enough...
Thread Starter
Staging Lane
Joined: Feb 2019
Posts: 94
Likes: 4
What control es the line pressure in my 1994 LT1 unit? Could that be defective and could the line pressure cause premature solenoid failure. Initially, the first symptom was hard shifting like a shift kit.
TECH Junkie
Joined: Jun 2008
Posts: 3,202
Likes: 1,390
From: Nitro Alley
As long as the Line-Pressure is rising quickly enough when the Throttle is pegged...
and there is minimal to no Clutch slipping...
Then all is good.
There should be no need to be concerned of Solenoid failure.
Any time the Line-Pressure is elevated, shift firmness should increase.
You should get a Line-pressure Gauge with a long hose...
tape the Gauge to the Wind-Shield and Drive the vehicle while monitoring the Line-Pressure.
Joined: Nov 2003
Posts: 6,216
Likes: 236
From: Wichita KS / Rancho San Diego
Plus as vorteciroc knows much better than I, the 94's had a funk factor as the transition to electronic control from the old 700R4 platform was in its infancy and the torque of the LT1 played havoc with an as yet underdeveloped transmission. Ask me how I know? I've owned two of them.