DTC 24 ('95 LT1/4L60e)
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Junior Member
Joined: Apr 2005
Posts: 32
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From: Ft Laud, FL
Car: '76 Vette
Engine: '95 LT1
Transmission: '95 4L60e
DTC 24 ('95 LT1/4L60e)
I also have this posted in the "transmission" section, but if the DTC 24 is my problem, thought I'd get responses here...Sorry if this is a "double-post" 
Have a '95 LT1/4L60e (in a '76 Vette) that's not shifting properly. When shifting manually from 1st thru 4th, it will only go down to 2nd, then will only shift up to 3rd (no 1st or 4th). When put in OD/(4th) and allowing the tranny to shift, it goes into 1st briefly, then there's a harsh shift to 3rd, where it remains (no 2nd and no 4th).
My SES light does NOT come on, but when logging w/ DataMaster, I get a DTC 24 (DM's definition: "Low tranny speed"). I've replaced the VSS w/ a Delco unit and wiring seems fine (I had recently spliced into the VSS circuit [ckt 400] to send the signal to an AutoMeter Speedo, but have since bypassed the speedo and soldered the wire back (just to rule out the speedo))
Shouldn't such a problem illuminate the SES? What else can I do to ensure a good VSS signal to the PCM? The SM has some procedures (for DTC 24), but all involve having the half-shafts supported...I have nothing like this in my garage!
If anyone wants to see my DataMaster file...please reply / e-mail me.
* I'm using an F-body PCM / Painless wiring harness.
Thanks...I'm out of ideas!
Have a '95 LT1/4L60e (in a '76 Vette) that's not shifting properly. When shifting manually from 1st thru 4th, it will only go down to 2nd, then will only shift up to 3rd (no 1st or 4th). When put in OD/(4th) and allowing the tranny to shift, it goes into 1st briefly, then there's a harsh shift to 3rd, where it remains (no 2nd and no 4th).
My SES light does NOT come on, but when logging w/ DataMaster, I get a DTC 24 (DM's definition: "Low tranny speed"). I've replaced the VSS w/ a Delco unit and wiring seems fine (I had recently spliced into the VSS circuit [ckt 400] to send the signal to an AutoMeter Speedo, but have since bypassed the speedo and soldered the wire back (just to rule out the speedo))
Shouldn't such a problem illuminate the SES? What else can I do to ensure a good VSS signal to the PCM? The SM has some procedures (for DTC 24), but all involve having the half-shafts supported...I have nothing like this in my garage!
If anyone wants to see my DataMaster file...please reply / e-mail me.
* I'm using an F-body PCM / Painless wiring harness.
Thanks...I'm out of ideas!
Thread Starter
Junior Member
Joined: Apr 2005
Posts: 32
Likes: 0
From: Ft Laud, FL
Car: '76 Vette
Engine: '95 LT1
Transmission: '95 4L60e
Just wanted to throw some more info out there...
Was just looking over my DataMaster file record-by-record, and noticed at the EXACT moment it shifts from 1st to 3rd (in 4th/OD) the following events occur:
Speed MPH goes from 2 MPH to 10 MPH
Force Motor (FM) Ref Amps goes from 0.92 to 0.16
Force Motor (FM) Act Amps goes from 0.94 to 0.18
TCC Duty Cycle (DC) goes from 0.00 to 90.19
I thought it was strange that ALL these occur w/in a 10th of a second. And why would the tranny shift to 3rd if it "thought" I was only going 2 MPH?
I'm still hoping it's something electrical ("Not too expensive"), rather than mechanical ("Expensive") My responses from the "transmission" section are saying it's probably my 2-4 band in the tranny, and I don't understand the DataMaster info above enough to rule that scanario out, but why can it engage 2nd when manually shifting (and not 1st or 4th) , but when in Auto/4th/OD, it engages 1st (and not 2nd or 4th)???
Was just looking over my DataMaster file record-by-record, and noticed at the EXACT moment it shifts from 1st to 3rd (in 4th/OD) the following events occur:
Speed MPH goes from 2 MPH to 10 MPH
Force Motor (FM) Ref Amps goes from 0.92 to 0.16
Force Motor (FM) Act Amps goes from 0.94 to 0.18
TCC Duty Cycle (DC) goes from 0.00 to 90.19
I thought it was strange that ALL these occur w/in a 10th of a second. And why would the tranny shift to 3rd if it "thought" I was only going 2 MPH?
I'm still hoping it's something electrical ("Not too expensive"), rather than mechanical ("Expensive") My responses from the "transmission" section are saying it's probably my 2-4 band in the tranny, and I don't understand the DataMaster info above enough to rule that scanario out, but why can it engage 2nd when manually shifting (and not 1st or 4th) , but when in Auto/4th/OD, it engages 1st (and not 2nd or 4th)???
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