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GEAR HEAD
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Discussion Starter · #1 ·
this thread of mine went sticky on gmt400.com and helped alot of people so i figured id post it here at well maybe help you guys out as well


Before guessing at transmission problems, check the fluid level (car warmed up, engine running in Park on level ground) and have the PCM scanned for trouble codes FIRST. This guide is meant for problems that do not show up as PCM codes (like shift A&B solenoid failures, for example).

NOTE: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.

Also note that many problems that show up as transmission issues are actually PCM or electrical, and may be external to the transmission. Try a different PCM, and check for chafing where the cables come out of the PCM.

Secondly, put a line pressure gauge ($55 shipped on Ebay, or visit a local trans shop) 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 0.500" boost valve (easy fix in pan).

Beware of coolant contamination - coolant will cause clutch packs to delaminate and thus cost you a rebuild! Trans fluid eats radiator hoses! If you find any sign of cross contamination, fix the problem and thoroughly flush both systems IMMEDIATELY.

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.

R&R = Remove & Repair (or Rebuild) = Transmission must be removed to fix the problem and may have to be rebuilt or replaced.

Common failures on 4L60E, symptom < cause > any possible repair:
1. Slow, slipping or no reverse: “lo-reverse” clutches are worn out, fluid leak in the reverse apply circuit, or broken sunshell. It is possible to remedy a fluid problem by removing the checkball from its cage in the case in the rear of the trans may help (must remove valvebody), or adding a high-viscosity additive such as Lucas Transmission additive or other seal restorer product. May also have worn boost valve (can replace in the pan).
2. 1-2 shift does not happen at WOT until you let off the gas: Best case: try replacing the TPS. Middle case: leak in the 2nd gear apply circuit (servo assembly or 1-2 accumulator). Doublecheck by using the pressure gauge and watch for a big drop when the PCM commands 2nd gear. Worst case: poor line pressure rise (see below).
3. 1-2 Shift shudder at WOT; delayed or abnormal 1-2 shift; There's a problem ONLY on the 1-2 shift: 1-2 accumulator piston cracked or stuck cocked in the bore. Check the yellow spring inside the accum housing for breakage. Also, if the accumulator housing walls are scored, the housing must be replaced. Easy fix in the pan.
4. 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.
5. 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.
6. No 3rd or 4th gear: “3-4” clutches are worn out. R&R. The car is safe to drive (in 2) until you can get it fixed.
7. Sudden grinding noise with no prior warning primarily in 2nd gear, behavior in reverse may be abnormal; sunshell is fractured. R&R. Try not to run or drive the car or further damage could result.
8. 1st and 3rd only, no 2,4 or R; sunshell is fractured or splines are sheared off. R&R. Try not to run or drive the car or further damage could result.
9. No 2nd or 4th gear. 2-4 band is slipping. Servo seals may be damaged (can be fixed without removing trans. Otherwise, 2-4 band is worn out. R&R.
10. Trans shifts into gear harshly, car feels sluggish off the line, No 1st, 4th or TCC lockup available, Manual 2nd, 3rd and Reverse are only available gears, CEL is on: Transmision is either in limp-home mode or has lost electrical power. If there are lots of error codes in the PCM, check the underhood fuse that powers the transmission, and if it pops again, look for a short in that circuit like an O2 sensor harness touching exhaust. Otherwise, check PCM codes for a particular fault in the transmission causing the PCM to put it in limp-home mode.
11. 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.
12. 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.
13. No TCC lockup: Brake pedal switches improperly adjusted (always on), TCC solenoid failed (easy fix in the pan), TCC clutch worn out (must remove trans and replace TC).
14. TCC always locked: TCC apply solenoid circuit shorted to ground, TCC solenoid blockage (easy fix in pan), or TC broken (must remove trans and replace TC).
15. Horrible noise in 4th and feels like the brakes are on: overrun clutches are applying due to a cracked or leaking forward piston. Overrun clutches will be worn out after 30 seconds of this behavior. Car can be safely driven in D. R&R.
16. 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. Transgo HD2-C kit fixes first two without removing trans. Seal restorer may fix last problem, but probably R&R. Also try a transmission flush with BG brand products (Firestone stocks it).
17. No forward movement in OD or D, but L2, L1 and R work: Forward sprag is broken. R&R. Try not to run or drive the car or further damage could result.
18. Extremely harsh shifts from P or N, normal shifts at WOT: EPC (Electronic Pressure Control) solenoid failed. Easy fix in pan. Fix as soon as possible or hard parts will eventually break.
19. Loud bang, grinding sound, loss of all gears, and a binding driveshaft: snapped output shaft. Try to wiggle driveshaft - if more than 0.020" play, that's the sign. R&R.
20. Trans seems noisy when moving in 1st and Reverse, noise goes away instantly if you shift to N or the trans goes into 3rd gear: Reaction planetary is worn out due to high miles or insufficient lubrication. Not a critical failure, but not a good sign either. R&R sooner rather than later.
21. No movement in any gear: pump failure, or total loss of fluid. R&R, or refill pan and find the leak. If out of fluid, avoid running the engine until the trans is refilled to avoid pump damage. To check for pump failure, check fluid level with the engine off, then start the engine and recheck fluid level. If level does not go down when engine is running, the pump is broken.
22. Transmission does not shift automatically, only manually. Swap in a known-good PCM, check wiring, check other sensors such as VSS and TPS.
23. 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.
24. Fluid leak out of the front of trans where the converter connects; partial or full loss of movement: Front pump bushing walked out. R&R. May have to replace converter also if hub is scored. Note that a leaking front seal usually means the bushing is walking out (i.e. call your local trans shop and schedule an appt.).
25. Torque converter shudder in 4th while lockup is engaged; problem goes away when the brake pedal is pressed slightly to unlock converter. Have a shop verify line pressure, and provided no valves in the TCC hydraulic circuit are worn, replace the torque converter. Also, Lubegard Shudder Fix will at least fix this for awhile. Or try a transmission flush by a shop that uses BG brand products.
26. Shift suddenly become very hard. When going from park to either reverse or drive it slams into gear. 1-2 and 2-3 shifts are also harsh. All gears seems to work. Problem may be intermittent: Check TPS for smooth electrical response. If the response is jumpy or erratic at all, replace TPS.
27. All fluid pumped out through the vent tube: Plugged cooler line. Flush the transmission cooler and cooler lines. Also could be overfiled transmission.
28. Car acts like it's in OD in neutral, car is locked stationary in R, engine feels loaded in P, all four forward positions work fine: R&R: Internal crossleak feeding the forward clutches all the time. Most likely a cracked input housing, or cracked forward piston means forward clutches are fused together. Car can safely be driven gently in forward gears until the repair.
29. Needle bearings in the pan, first gear and/or reverse may be noisy: Either a torrington bearing or a planetary bearing is on its way out. Trans will eventually die a loud, catastrophic death. Cheaper to rebuild now (saves further damage to hard parts), but requires R&R. It is drivable until it breaks.
30. 1-2 or 2-3 shift is slow/soft above part throttle: Trans is on its way out. R&R.


I monitor this thread alot and if you have any questions feel free to ask and ill do my best to answer
 

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I got one for you, but it's a 4L80E. Truck is an 04 2500hd. Trans was rebuilt in September. Since then the trans temperature goes up to 200* under normal unloaded highway driving, even when outside temps were 30*. It will climb over 200 in stop and go. I replaced the factory auxiliary cooler with a long tru cool max 40k cooler and no change, other than it takes a little longer to heat up. Cooler circuit is flowing good. Trans shifts well through all gears and tcc locks up. Only other issue is sometimes when it's warm, it will clunk into gear and stall the engine when going from drive to reverse. But only drive to reverse. Reverse to drive is fine, park to reverse is fine. I've verified the sending unit and gauge are correct. Thoughts?
 

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GEAR HEAD
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Discussion Starter · #3 ·
I got one for you, but it's a 4L80E. Truck is an 04 2500hd. Trans was rebuilt in September. Since then the trans temperature goes up to 200* under normal unloaded highway driving, even when outside temps were 30*. It will climb over 200 in stop and go. I replaced the factory auxiliary cooler with a long tru cool max 40k cooler and no change, other than it takes a little longer to heat up. Cooler circuit is flowing good. Trans shifts well through all gears and tcc locks up. Only other issue is sometimes when it's warm, it will clunk into gear and stall the engine when going from drive to reverse. But only drive to reverse. Reverse to drive is fine, park to reverse is fine. I've verified the sending unit and gauge are correct. Thoughts?
hmmm thats a good one, do you have a warranty with the transmission? it almost sounds as if there is fitting issues, in a transmission the #1 creator of heat is friction, now from september till now i would suspect that you would have slipping issues if that were to be the case...... now as far as the clunking goes, i have a test for you, when it gets hot like normal and starts clunking, stop and unplug the battery for 5 minutes and then plug it back in and see if it still does it, if it stops then that tells you that its a electrical issue, also do you know if your torque converter was replaced in the rebuild?
let me know what happens
 
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Yea I have a warranty so I'm not worried about it. I'm just troubleshooting along with the transmission shop to find the actual cause before we just throw another transmission in.

Torque converter was replaced with the rebuild. We put another one in just last week and same issue. The stalling in reverse actually got worse since then, as in it does it more frequently. It had never done that prior to the transmission being replaced. It only happens from drive right to reverse. If I go drive, neutral for a second, reverse, it still shifts a little hard but no stall.

It's puzzling to everyone I've spoken to. The clutches and drums look brand new and show no signs of wear or overheating. Everything points to something wrong in the transmission, but we don't know what. I feel it's going to be something stupid like a bad pump that's going on bypass or a bad o ring or something somewhere causing a small internal fluid leak. But who knows.
 

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GEAR HEAD
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Discussion Starter · #5 ·
completely possible, but hey thats what warrantys are for, you paid good money for the tranmsission, its their job to make sure its running well
 

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You're correct, 4 speeds with torque converter lockup which is overdrive. However if it goes into overdrive it has to have been in 4th gear already to do so. You can verify what gear your truck is in with a scanner.

I noticed when driving around easy, I sometimes wouldn't even notice the 3-4 shift until I looked at the scanner while driving and noticed it
 

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GEAR HEAD
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Discussion Starter · #12 ·
You're correct, 4 speeds with torque converter lockup which is overdrive. However if it goes into overdrive it has to have been in 4th gear already to do so. You can verify what gear your truck is in with a scanner.

I noticed when driving around easy, I sometimes wouldn't even notice the 3-4 shift until I looked at the scanner while driving and noticed it
very good sir, alot of people dont know that there is a difference between, 4th gear and lockup, but as far as mechanically its all the same clutches
 

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GEAR HEAD
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Discussion Starter · #13 ·
I got a weird one. my truck only seems to shift into 4th when under "load" otherwise it seems to skips 4th almost and goes into overdrive...
when you let off and there isnt anymore load, does it release from OD?
 

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GEAR HEAD
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Discussion Starter · #15 ·
No GM transmissions freewheel like that. It'll downshift to 3rd if you accelerate or continue to lose speed. The PWM lockup strategy can make a little difficult to discern whether the converter is locked unless you eyeball the tach.
my 97 has a 2000 stall converter and under load it will lock into OD but as soon as you let off it unlocks and sets at about 2000 rpm, i was wondering if your was doing the same
 

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Got a question for ya. My 07 nnbs is poping out of reverse when there is a decent amount of gas or backing up a hill. Everything else works fine but when pressure is added backing up it pops out and grinds like if it was put in park when moving. It's got me what is causing this cause all other gears work fine. The truck is a 2007 Silverado crew cab 1500 4wd with almost 150000 miles. Help please
 

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I just got a 05 Silverado z71 1500 5.3, the guy said he has a bigger alternator so he ran a wire to the pcm fuse.. and my 4l60e only has 3rd and reverse. I change the internal wiring harness and all the solenoids, still only 3rd and reverse, and is saying a couple of my solenoids are shut off..I had a buddy try to turn them on manually, would not work and is saying service charging system, and if I hit a bump it will throw it into reduced engine power mode... PLEASE PLEASE PLEASE HELP
 

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My 01 Sierra C3 - 6.0l;
Mine started not wanting to come out of 2nd going into 3rd leading up to this issue of P0300 and not wanting to shift and just revving higher in the RPM's, until I relaxed my foot and eased off the Gas pedal then it would shift. I have never had any major problems with this beast. This problem here ìs getting me and my wife's Blood Pressure up quite a bit. Mileage was right àround 96,666 when this whole thing began. Ì have replaced Spark Plugs, Wires and I am working through the Coils, checking spark at every move just keeping an eye on them for any type of short, or anything. Replaced all Spark Plug Wires along with, Fuel Regulator, TPS, also cleaned Throttle Body(Off of Vehicle servicing)also cleaned out the K& N Air Filter(Cold Air Intake System). I have been showing that my Fuel Banks are at very uneven pressure volume % when I take a "Blue Diagnostic" scan and run a Code Check. I take a Snapshot of 2 Data points during my Test Time. The "Blùe Diagnostic Analyzer" plugs into my OBD11 Port. It is supposed to be at the top of the list when it comes to Scanners best Diagnostic systems. I purchased this for my this headache. Like I said, " I've never had any type of Fuel Delivery problem before or any other Driveability or Performance problems ever, for that matter.
(I'm the Original owner)
"I apologize for the long winded summary - I did "Not" want to leave any important symptoms out." I am losing more hair by the hour guys and gals! HELP...PLEASE?

Signed,
. "Frustrated!"
 

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I have a 00 silverado n the planetary snapped tore trans to hell well I took 3 to make one since w everything I used was all good pump n all jus has to use a nother trans housing n replace the planetary used same pump n all other insides well w that said I installed everything n all got everything to fit n line up filled w fluid n fired er up well it don't seem like it's goin in gear reverse nuterel drive first second third NUTHING u can usually feel truck engage in a gear or hear it well it's NUTHING it's pumping fluid what would be my problem here other than not being a mechanic would this may be a silonoid or nutreal switch n shifter inside not functioning properly I'm stump
 

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I have an 04 suburban 1500 Z71 with 108,000 on it (yes 108k). I have several issues and think all are related. Runs great but after about 20 minutes of driving it up shifts hard 1-2-3. Had the trans serviced no change. Also when this happens I get static in my speakers even when the radio fuse and amp fuse are pulled. My mirrors don't hold their preset nor does the seats. Any help would be great
 
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