Transmission 4T60E Rough Shifts??

[The_Cams]

I recently developed a problem up shifting at the 40ish mph and 50ish mph marks while traveling up inclines (hills). My 1996 Buick Regal, 3.8L shutters and won't upshift at these speeds in overdrive. In 3rd, I can coax it, but it can be rough. Feels like the timing is off. No codes have appeared.

Car history. This is a GM SRTA transmission replaced in 2002, at 93500 miles (86,410 miles ago). Currently have 179910 miles. The fluid looks great (clean, smells fine), replaced 13500 miles ago, Quaker State multi vehicle/Wix filter. I normally drop the pan every 24, 000 miles.

I originally felt the trans rough shifting after replacing a broken coolant elbow (the plastic one that runs from the LIM to the tensioner). I had tried to get up a steep driveway in the rain, spun the wheels upon accelerating (in 2nd gear), backed down the driveway, and the coolant elbow had split (thanx Dexcool). After the fix, the trans started shifting rough at 40 and 50 mph up inclines.

I replaced plugs and wires (scheduled maintenance), and the vacuum looks good and steady at 22Hg. Car seems to idle fine.

Could a worn tensioner cause belt slip and be the cause of this under load? Bad fuel injector or fuel pump maybe? Or should I just have the transmission checked out?

Any input would be greatly appreciated.

[00Beast]

I would check the ignition first. A lot of similar issues like this have been ignition related, not transmission related. I'd check your coils with the guide in Techinfo: viewtopic.php?f=48&t=1683 . What brand plugs, what brand wires did you use? Take a look at your records and see if anything on the list below hasn't been done in a while. Making sure all of those items are good can ensure that your issues aren't due to lack of maintenance.

Brand Suggestions are in the parentheses.

• 1987-2005 Bonneville / Buick 3800 Maintenance List
  
  Run Seafoam through gasoline and intake every 5,000 miles. One pint of Seafoam in a half tank of fuel is a good mix. The intake is optional, but recommended.
  
  Grease: Ball Joints, Tie Rods Every 8-10k ( Green Grease recommended)
  Air Filter Every 15k (Amsoil EaA, Purolator PureONE)
  PCV Valve Every 30k
  MAF Sensor Element Cleaning/TB Cleaning Every 50k viewtopic.php?f=48&t=1661
  Fuel Filter Every 15-25k (Purolator, AC Delco, WIX)
  Spark Plugs Every 30-50k (NGK TR55 or Autolite 605) (Never Bosch)
  Ignition Wires Every 30-50k (Napa Belden, AC Delco, Autolite Pro, NGK) (Never Taylor or Bosch)
  Oil & Filter Every 5-6k or Every 6 months (Mobil1 or Amsoil)(Mobil1, Purolator PureONE, Amsoil EaO or WIX) (Never Fram) viewtopic.php?f=45&t=214
  *Conventional Oil Every 3k/3 months(Pennzoil with a WIX (Napa), Delco or Purolator filter)
  Transmission Flush Every 15-20k (Always make sure filter is changed when flushed)
  Cooling System Flush Every 25-50k or 3-5 Years (Peak or Prestone Green Coolant Only) (Never Dexcool)
  Oxygen Sensor Every 80-100k (30k for non-heated) (AC Delco or Denso) (Absolutely never Bosch) viewtopic.php?f=48&t=794
  Accessory Belt Inspect every 15k, replace every 100k, or as needed
  Cabin Air Filter Inspect and Replace every 15k, or as needed in dusty conditions. (Note: 00+ Only)
  Evap Core Cleaning Whenever Needed (Note: 99 and older only) viewtopic.php?f=45&t=2432
  
  *Special Considerations*
  All 3800s, LG3, LN3, L27, L36, L26, L67 & L32, especially important on vehicles factory installed with orange Havoline Dexcool Antifreeze/Coolant: http://www.dex-cool.net/
  Lower Intake Manifold Gasket Replacement, every 80-100k (ignorance of this can allow coolant to enter your engine oil, this happening can cause irreversible lower engine damage, requiring replacement of subject engine)
  
  Series II, Naturally Aspirated, RPO:L36:
  Upper Intake Manifold Plenum Replacement, Every 80-100k (ignorance of this can allow coolant to enter your intake manifold, possible damage to occur can be hydrolock, irreversible damage to emissions devices, misfires, etc. Most times, engine replacement is required if ignored long enough.) viewtopic.php?f=53&t=1061
  
  Series I, II, III RPO Code L67 & L32:
  Change Supercharger Oil; Every 30-50k. (Intense Racing or GM Dealer) viewtopic.php?f=56&t=1690
  Supercharger Belt; Inspect Every 15k, Replace Every 100k or as needed.

[The_Cams]

Yeah, I've pretty much covered the maintenance checklist. Didn't grease the tie rods, but had them looked at along with the ball joints recently, and the mechanic said they were fine. Need an alignment

Plugs were autolite app606 (double plat's). Wires are Standard Motor Products.

[00Beast]

Hmm. I'm not sure whether the 3800 N/A cars like platinums. I know some members have notices GAINS going back to copper core plugs on the L36. Someone else may chime in on the consensus of the gearheads on platinums.

[The_Cams]

I've run the Delco 41921's for the life of the car with good results. Being that the trans shifting began before I replaced the plugs, they are probably acceptable. Something to monitor though - thanx.

[The_Cams]

The latest update is that I swung into AAMCO this morning to take advantage of their free trans check. They determined that the tranny is fine, and this is an engine issue, possibly fuel related. They think Fuel Pump or Injectors. I'm skeptical, but they were adamant.

I have an appt to bring it into the dealer tomorrow (Thursday). See what they recommend.

[sandrock]

The problem with transmission inspections...FREE inspections I should say...is that all they will do is plug into the OBD2 port to see if any tranny codes come up. If not, they deem it good. But all that proves is that it is *electrically* fine.

Platinums...no matter what or who makes the plugs...do not like having reverse current flowing through them (i.e. waste spark systems, just like what we have). I tell people either go copper or irridium, never platinum. Auto parts stores also don't care about that little tidbit of info. They will sell whatever the paying customer wants or is suggested to them.

Replace your plugs, make sure your O2 sensor and any of your rear plug wires do not cross or come near each other, and make sure the coil plate is clean and the terminals aren't corroded. Also, it won't hurt to apply heatsink grease in between the ICM and the mounting plate...the plate not only acts as a grounding point, it also acts as a heatsink.

[The_Cams]

The Aamco guy didn't even plug his 'transcan' in to check the OBII codes. I had told him I scanned it, and there's nothing stored. He did take it for a ride and claimed it to be an engine issue, and proceeded to try to sell me on a $185 diagnostic. Hey, he's in business after all

I wish I had a fuel pressure gauge handy, but don't have a lot of time to play.

I went through the coils last night. They're clean and ohm out properly. Engine runs smooth, no codes. Wires are routed by the book, and clear of the O2 sensor. This all started a week prior to replacing the plugs from plat to plat, but I may try the Iridium as suggested. Time is my enemy now.

Thanks for the recommendations.

[The_Cams]

Update. I went to the Buick dealer, and they confirmed a misfire (I was babying the shifts). He was a tad more assertive with the accelerator and had the misfire P0304. The tech narrowed it down to either the #4 plug, wire or fuel injector.

Freeze Frame:

P0304 - Misfire
Fuel System 1: OL
Fuel System 2: CL Fault
Calc load %: 41.57
ECT (degree F): 195
STFT B1% -0.78

The tech also said he replaced the #4 plug and wire, and it didn't misfire until he wet the wire. He said the coils, fuel pump are fine.

He suggested replacing all plugs and wires to AC Delco iridium and AC Delco wires (Same as a few posters suggest I do; thanx 00Beast, Sandrock). Then swap fuel injectors to see if the misfire moves. The cost was $96 at the dealer (not bad).

I think I'm just going to buy a new fuel injector and replace the # 4 injector and see if that fixes the problem. I could toss in an iridium with a new wire and see if that helps, but the same problem has repeated with an AC Delco 41-921 and APP606, plus 2 different wires (AC Delco/SMP). Any thoughts?

[The_Cams]

Replaced spark plugs and wires with AC Delco wires and AC Delco Iridium plugs. Much, much better performance, but still occasional misfire and stumbling when shifting at about 45 mph and 55 mph.

Pulled fuel injectors, and found the injector to cylinder 3 to be bad. missing lower plastic pieces (orings, etc). Just metal. Obviously not sealing properly.

Replaced with new number 3 injector ($75 at AZ). Problem solved! Runs great!

[tan96ssei]

now some one correct me if i am wrong but i have noticed that regaurdless of aspirations that the 4T60E in my old 92 SE and the comparable HD version trans in my 96 all stutter in a sense at that range. reason i figured out through techII scanners and my DHP scanner on my 96 is that our TC kicks in around 45-48 MPH obviously the TC lock is different according to how hard you accelerate. so could your "up-shift" problem be a result of your driving habits (light on throttle) along with TC lockup? i noticed too that to overcome climbing a hill around the 40-50MPH marks with TC locked you need moderate throttle angle (more than half pedal travel) to have the trans downshift and give you more RPMs and equally more torque.

so long story short can it be something as simple as the TC locking up and your lighter foot driving habits that are the cause?

[The_Cams]

What you describe is correct for the 4t60e. I can feel most shifts. This was greatly out of the ordinary as it would throw a code occasionally for a misfire going up a hill. Dropping down to third would help a bit, but not give much power.

Now that the injector has been replaced, it runs fine up hills. Can still feel the shifts, but not stumbling and throwing codes.