Question about 1991 Chevrolet C2500

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1991 3500 gmc wont shift stays in seconed gear

Old trans did same thing put good used trans new does same thing replaced speed sensors, cleaned plug, differnt comp.gage clustter replaced looked at harness trans will only drive in second gear if u reset comp. and then it will start out in 1st and slam second and then goes in to limp moded and wont shift have had computer hooked up to it and it doesnt show any thing wrong with it. i am at total loss what do u think

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Many transmission shops have a "flight recorder" that they can attach to the system and drive the vehicle. If that has not been done perhaps it will help. Odds of getting another transmission with the exact problem as the original are pretty slim, so I'd tend to think its on the control side. Have you checked the MAP sensor? often the shift module gets its info from there too.

Posted on Jul 22, 2009

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My 1994 GMC Suburban wont shift out of first.....but will shift to second manually but wont go any higher........?


Sounds like a vehicle speed sensor, it governs shifting based on engine RPM vs Transmission RPM among other things. Located usually on the rear tailshaft or rear transfer case on the majority of 4L60E automatics.

Mar 25, 2015 | 1994 GMC Suburban

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On our 1996 gmc jimmy I replaced the transmission now it will not shift at all. did I miss something?


Did the old transmission do the same thing? Could be the control module or bad wiring. Could be you got another bad transmission.

Jan 24, 2015 | 1996 GMC Jimmy

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I have a 2008 GMC Yukon XL Denali. I hit a small snow drift yesterday and now my speedometer stopped working, my RPMS are bouncing, oil pressure is bouncing, temp is bouncing and vehicle wont shift out of...


Vehicle speed sensor, wheel speed sensor, your VSS operates you MPH and tells the trans how fast you are going and when to shift, it is telling the trans that your not moving so why would it shift? Next your ABS wheel speed sensor tell the car what wheel is moving at what speed to activate traction control and abs systems both are very sensitive and easy to break

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Transmission


yes the computer uses the speed sensor to tell the trans when to shift. you need to find and plug back in.

Mar 25, 2013 | Cars & Trucks

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I have a 2000 GMC sierra 2500 truck. The guy I bought it from had a new transmition put in it. After driving a while I noticed that the tranny wouldn't shift into low gears 1st & 2nd on comand. and...


-----check possible tps [throttle position sensor ]circuit for damage or faulty sensor----if good check the fuses and trans harness for shorts damage or disconnection,check o2 sensors wiring possible ground to exhaust ,or internal leak 2nd gear apply circuit[servo assembly or 1-2 accumulator] or poor pump pressure

Feb 13, 2010 | 2000 GMC Sierra

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What is the speed sensor problem with these trucks? My 1996 GMC Sierra, sort of bucks when using cruise control and there is a need for the trans to shift, could that be speed censor? Same thing happens...


Check or replace the TPS (Throttle Position Sensor). If you have a speed sensor problem, you would not have speedometer and cruise control.

1-2 shift is delayed and harsh, may not shift into OD: Check TPS for smooth and linear electrical response over the entire range of motion. If not, replace.

Soft shifting, gradual performance degradation: Poor line pressure rise due to leaking boost valve, clogged EPC filter screen, failing EPC solenoid, or worst case: leaky seals throughout the transmission.

When you can dig up some money, have a transmission shop put a line pressure gauge on the pressure test port and go for a drive to verify proper line pressure. Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out. If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.490" or 0.500" boost valve (easy fix in pan).

Good luck and keep me posted, be glad to help you get your transmission running 100% again soon and check the level and condition of your transmission fluid.

Jan 24, 2010 | 1996 GMC Sierra

1 Answer

My GMC has 311632 miles on it. I just changed the 4L60E transmission a few months ago and now it wont shift out of first unless I manually put it in second gear. all the gears from park rev. nuetral works...


The transmission may be in Limp mode. The transmission is on the same fuse as the MAF, O2 sensors and at least one other sensor - if an O2 shorts out, it will blow the fuse and the trans will go into limp-home mode. Be sure the trans has power and the fuse is not blown before doing anything else.

What is "limp-home mode" ? This is a fault mode in which the transmission either loses electrical power or the PCM deactivates all of the electronics. The transmission will default to max line pressure. The driver will have Reverse and 3rd, with manual 2nd available by putting the gearshift in 2 or 1 (doesn't matter). 1st, 4th, and TCC lockup will not be available. It will not hurt the car to drive it like this for short periods, but use manual 2nd to get the car moving, and be aware that the trans will generate more heat than normal while operating in limp-home mode due to increased torque converter slippage during 2nd gear starts and no lockup in 3rd gear.

Trans does not upshift out of first, speedometer reads zero at all times: VSS failure. Easy fix on rear of transmission, but xmember must come out to access VSS.

Car goes into gear but feels very sluggish like the brakes are dragging, but it will roll easily (starts out in 4th gear), you manually shift to 2 to get it moving, once it's moving you put it back in OD and the car shifts 3rd to 4th on its own and locks the converter at the appropriate time: ShiftB solenoid failed: Easy fix in the pan. Or a wiring problem from PCM to trans.. or PCM.

No 1st or 4th available; trans shifts 2nd to 3rd by itself in D or OD and locks the converter : ShiftA solenoid failed. Easy fix in the pan. Or a wiring problem from PCM to trans.. or PCM.

Transmission does not shift automatically, only manually. Swap in a known-good PCM, check wiring, check other sensors such as VSS and TPS.

3rd gear starts, can manually shift through all gears. When car has been turned off for a bit, then back on it will run normally.: VSS dropoff w/ Hi-stall converter. The rpms are too high, but VSS is showing no movement. Happens after a tire burning take-off. Doesn't store a code, will not throw a CEL (I've heard that it will store a code if it happens 3 or more times). Cure: Reprogram PCM for VSS dropoff -- PCMforLess knows about it.

Here are just some of the common things you have described with the issues your transmission has. Good luck and keep me posted.

Dec 22, 2009 | 1994 GMC Sierra

1 Answer

2002 - Starts off in third gear and stays there.


Transmission speed sensor located on trans. is malfunctioning, replace.

Jul 03, 2009 | 2001 Volkswagen Beetle

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1993 GMC 1500 4x4 poor shifting


this may be due to a poor connection at the vehicle speed sensor on the transmission, pull the connector off the sensor and clean it with contact cleaner, if the problem persists replace the speed sensor. there are 2 diff ones here is a picture of the most common one for an auto trans.3deea43.jpg

Mar 26, 2009 | 1993 GMC Sierra K1500

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