4l60e strange behavior

[Sharkbaithuhaha]

Hi I recently picked up a 2002 single cab shortbed silverado with a 4.8. Its a fun little truck and i wanna get some more power put of it but one of the first things i noticed was that when coming to a complete stop while breaking it feels like the transmission shifts into neutral with a clunk and then clunks back into gear when I accelerate away from the stop. Truck had 147000 miles and is in really good condition. Transmission fluid is red and does not smell burnt to my nose. It also feels weird when shifting at more than 50% throttle almost like it slips towards the top of the rpm range and then as its shifting catches again and pulls hard DURING the shift and after. Pic for attention
I know the crappy hood “scoops” need to go but i wanna get this problem fixed before i put a cowl hood on it

[SMWS6TA]

Has it ever been rebuilt?

Could be time up for the stall converter?

Mine started like that with my Grand Prix

[Sharkbaithuhaha]

Would there be debris in the transmission fluid if that was the case? I might throw a cheap converter in it just to see if it helps. If its not the converter though i might just say screw modding the 4.8 and save up for a 6.0/4l80e swap


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[SMWS6TA]

A piston and crank change and you can go from a 4.8 to a 5.3 and have really good gains in power and torque. Be a little cheaper than a 6.0L build. But with that truck I'd make it into a street truck and go for the 6.0L with a stroker. Or keep the crank, get the 5.3 pistons and get a turbo setup. Using the shorter stroke (it's called de-stroking) you can spin it higher (7000+ rpm) with a custom cam and build more boost.

Depending on what I was doing with the truck like track use maybe do a 700R4 instead of the 4lshitty. 4L80's take a bit more to swap into. New harness, tuning, and maybe a new driveshaft and cross-member just off the top of my head.


Only on a massive failure would you see it in the fluid. It can't hurt to drop the pan and change out the filter while there to take a look.


Also a shady trick when selling a used vehicle that you know has tranny issues is to change the fluid. Another a-hole trick is to use packing grease on the valve body. It runs good for a few hundred miles then the tranny just shits itself after you've had it. Seen it done.

[Sharkbaithuhaha]

With a 5.3 crank wouldnt i need to rebalance and tune it anyways? I was thinking if i bought a 4l80 and 6.0 together the 6.0 would bolt right up and the 4l80 would need cross member a little bit of wiring and some massaging of the trans tunnel. I wouldn’t put it past them to have pulled some tricks on the truck to get it to sell, but i also wouldnt be surprised if it was just a little tired. My friend has an 01 ecsb gmc and his 4l60 let go under pretty normal driving conditions with maybe 20-30k more miles on it. Im trying to turn this into a street bruiser muscle truck that’ll give any factory muscle car a run for their money (obviously not counting hellcats/zl1s/gt500s etc) and my goal is 500ish to the tire. I was gonna order a trutrac dif and either 3.73 or 4.10 gears for it. I may order a converter as well but id rather not throw money at a transmission thats getting ready to let go soon anyways. Id also obviously rather not put a 4l60 back in it. I have a th350 sitting in my garage but I’d like the overdrive and not have to fab something up just to put another ticking time bomb in it. Will 700r4s hold that kind of power? If im gonna have to buy a transmission that’s already got better guts i figured i may as well start with something solid ya know?


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[SMWS6TA]

I see your point in all you said. Yes the 4L80 is far far better over the 60 but there are still some issues with it IIRC.

I've seen a lot of f body's here running Turbo 350's and 700R4's that have been built up on 500-700hp cars at the tracks here.

[pajeff02]

How about a badly worn u-joint in the driveshaft?

[sjgreen6]

See if any of these sound familiar to you.

Common failures on the 4L60E transmission:

Symptoms with possible repairs:

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 valve body), 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). Double check 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 vacuum 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: Transmission is either in limp-home mode or has lost electrical power. If there are lots of error codes in the PCM, check the under-hood 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 : Shift A 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: Shift B 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 drive shaft: snapped output shaft. Try to wiggle drive shaft - 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 drop-off 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 drop-off -- 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 an over-filed 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 cross-leak 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.