Just wondering. We purchased a 1992 Bonneville SSE N/A new for the wife, November 1991. We put 305,000 miles on the car with the original engine and transmission, never anything but maintenance. We stopped driving it because it would not pass emissions. I purchased a 1 owner 2005 Bonneville SE with 58,000 miles on it in 2013(?). The car seamed to be properly maintained. At 112,000 miles the transmission failed.

I think the 4T60E is a better transmission.

What is your take on the 4T60E vs the 4T65E transmission.

Thanks for the input up front. - BC

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In Memory of Brad - 1/21/1977 .. 10/23/2013 ...... Aaron - 1977 .. 2017 .....
2017 Hyundai Santa Fe Sport ..... 1992 Bonneville SSE 1SB 170 HP L27 4T60E retired/sold to MattStrike ..... 2005 Bonneville SE 1SC 205 HP L36 4T65E - retired/salvage yard ..... PBCF user 2321

My take is that GM made a good transmission bad by bean counting it down. The 4t65e is inherently stronger than a 4t60e; but lack of auxiliary cooler, cheap seals without enough lip, poor PCS design/placement, and non-hardened parts where they are needed all contribute to early failures of these units. All of this is correctable with aftermarket parts (upgrades, shift kits, etc.) and it makes for a reliable trans. And of course there are plenty of aftermarket performance parts for the 4t65e.

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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

The 4T60 seems to have less common issues, and with that handles general neglect or lack of service pretty well and for longer than the 65.

My 2003's trans is still going great at nearly 180k miles. Only gives me the very occasional delayed engagement issue. However, I've been pretty good about taking care of it. It's had its fluid changed a few times, two different shift kits, and I think most importantly the cooler.

Back in the day, I was hardly gentle with it too.

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

The 60e has a stronger chain and gears. People used to swap these into the 65s way back when. The vacuum modulator also meant there was one less solenoid to fail. Less 4th clutch hub failures too?

The 65 has a better pump, revs higher without issue, better diff option, and can generally handle more power in stock form. Not to mention GM racing div basically figured out how to make it bullet proof.

It does seem that a 60 behind a S1 will last longer than a 65 behind a S2 but I'm not so sure that's a fair comparo. I feel like most 96 S2 L67 SSEis had premature 60e failures.

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95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

I've beat my 03 ssei many times in the 5 or 6 years I've had it. Plenty of burnouts for the grandkids and, a few for grandma but, I cant take her screams any more when I do that. Once in a while the trans stutters when I drop it in gear, other than that it shifts nice at 157K. One thing I forgot is that on the passenger side of the trans output shaft housing, there are 4 threaded holes, one of the bottom holes started leaking trans fluid a few years ago so, I found a bolt and siliconed it in. No idea what happened, something sure did.