Anything I've had break on a 4t65 has mostly been of my own doing. The only time I've had an issue with one was the last time I got one from the U-pull ($80) and slapped it in without checking any of the electronics or really going through it. Most of it's issues are fixed with a shift kit and trans cooler, and if it's older than 2003 the 4th hub.

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Boost addict


The Fleet:
'93 SSEi - Twincharged + manual Build thread
'97 Camaro - Top swap
'05 STS - V8, AWD, her DD
'92 Trofeo - Fair weather DD
'99 Montana - top swap 3800
'04 Sierra 2500HD - LLY Duramax

Current project:
Something cool, trust me.

Upcoming projects:
'92 Bonneville SSE
'87 LeSabre T-type
'67 LeSabre

Gone to greener pastures:
'84 Sierra Classic - Twin turbo 3800
'97 LeSabre - Top swap

RIP:
'86 LeSabre - pictures
'93 SE - L67

Rebuilds are often questionable because some shops just do not spend the time nor money to rebuild them properly. They cut corners. Often times parts that should be replaced are "reconditioned", meaning cleaned up, checked for specs, and thrown back in.



There is perhaps not much comparison with Toyota because they are one of the top dependable brands.

Gm transmissions are typically way better than Ford or Chrysler. Well, ANYthing is better than Ford transmissions.

My room mate and I, between us, have owned a few GM cars (90 cavalier, 99 lesabre, 94 Grand prix, 97 grand am, 99 grand am, 00 Bonneville) and the only problem I have seen was my 90 Cavalier had a torque converter clutch solenoid failing. I think at some point before my room mate bought the Bonneville, the trans had been rebuilt because the fluid is cherry red. None of the other fluids looked good so I doubt they made a special effort to change the trans fluid.

But anyways, my experience is GM transmissions are not overly troublesome. HOPEfully the rebuild in my room mate's car holds up, I know what I said about rebuilds earlier.
Ford ones though, do not get me started.

Wow, so many responses!

Update coming soon everyone. Car should be finished by the weekend and I'll post info and pictures once I get it back home.

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2003 Pontiac Bonneville SSEi (L67) - Galaxy Silver Metallic
1996 Chevrolet Camaro (L36) - Sebring Silver

I installed an HD cooling radiator on my 03 several years back, along with a shift kit, and Dexron 6 fluid changes since I bought it.. 160k on the clock.. Not as may miles as you, but shes still kicking..lol

Heat is a huge enemy of these transmissions.. I don't care what GM says, 160F trans temps are optimum in my eyes.. If the fluid becomes brown the trans has already been overheated and the damage has begun.. All 00-05 3800 Bonneville did not have a good cooling system, The radiator was just too skinny and allowed the trans to get too hot.

I think the stock cooling system was fine for the motor, but the addition of an extra transmission cooler and a 180* thermo and tune are a big help all around!

I did the same thing you did. Added shift kit, cooler, and I have a tune for the 180 thermo. I rarely see over 160 degrees for the trans unless it's real hot. I actually end up blocking the thing for half of the year. The car climbed and descended Pikes Peak without any issues or big heat.

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-Car Guy Carl
"Penelope" - 2003 SLE - 247k Miles
"Sydney" - 2000 Honda S2000 - 98k miles

Hey so I was going to post an update with pics, but I'm just going to type it out instead since I never seem to find the time to put everything together.

I ended up having the car towed down to back where I grew up (5+hrs away). My Dad, who is recently retired, decided to make an adventure of it and rented a U-Haul and a car trailer, leaving me his wheels for two weeks to get around.

The transmission has been completely rebuilt to well above the standard by one of the best GM Transmission repair shops anywhere.

Despite the fact that I am a grown ass adult, my parents were nice enough to foot the bill so long as I forgo my next several years of birthday and Christmas gifts.

I've been taking it easy on the car since I've had it back and yesterday I finally decided to push it a little to make sure everything was, in fact, in order.

It wasn't.

But it wasn't the transmission! Generic OBDII code for Cylinder #4 misfire. (which is of course one of the ones on the back of the engine).

I left work early yesterday as I wasn't feeling well (this has now turned into a full blown illness, but at least I got the work on the car out of the way as I descended into my sickly state) and started troubleshooting.

It wasn't the spark plug, although they're exhibiting signs the engine is running hot. I replaced the thermostat with a 180 degree T-stat, but I should also install new plugs that are a heat range colder I think.

Anyway, I switched #4 and #2 and got the same code when I took it onto the highway and laid into the throttle.

The new ZZP wires looked good, no burns or anything, so the next thing I tried was the ZZP coil pack. I swapped an old OEM one in and sure enough, no more misfire.

Disappointing as hell considering I just installed them at the end of last summer, but at least I fixed my problem. I'll order fresh OEM coil packs next time I have some cash to put an order through with RockAuto.

The car really scoots, and the transmission feels solid again. Here's hoping I can get several more years out of this beast.

Thanks everyone for commenting and offering advice!

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2003 Pontiac Bonneville SSEi (L67) - Galaxy Silver Metallic
1996 Chevrolet Camaro (L36) - Sebring Silver

The ZZP coils and wires have been known to be of somewhat spotty quality over the years. I wouldn't worry too much about it!

Glad to hear you got it repaired and are enjoying it again.

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-Car Guy Carl
"Penelope" - 2003 SLE - 247k Miles
"Sydney" - 2000 Honda S2000 - 98k miles

so after two pages, the first response was correct? lol...good you got it sorted.

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poverty forces one to do unorthodox things

2000 SSEi
past rides:
1996 SSEi
1992 GTP
1987 Grand Am

Nah, I think his issue still required a rebuild trans but after it all the ZZP ignition stuff decided to *shoot* to bed. Just bad luck and timing.

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-Car Guy Carl
"Penelope" - 2003 SLE - 247k Miles
"Sydney" - 2000 Honda S2000 - 98k miles

^ Yes, that.

The misfire may have been there all this time to a lesser extent or it may have just started recently.

It may have caused further damage to the transmission, but may not have been the only problem with it. The guy who rebuilt it said he saw things buggered up with the third clutch (going off memory, I know nothing of trans internals) he had never seen before and he has rebuilt dozens of these.

Anyway, Transmission fixed. Misfire also fixed. Here's hoping only little things from now on. That being said I need to go buy a new headlight. The fun never stops.

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2003 Pontiac Bonneville SSEi (L67) - Galaxy Silver Metallic
1996 Chevrolet Camaro (L36) - Sebring Silver