CC Mail Bag: GM’s Transverse Automatic Transmissions


Recently a reader noticed some comments I’d made about GM’s 4L60E transmissions – specifically, how they don’t like to hold together later in life, especially when behind V8s and/or when used for towing. An email conversation ensued, with both of us sharing our experiences.


As many of you already know, I’ve had to replace more 4L60E’s than I care to recall. This was the comment that started it all, which followed an article involving Suburbans:

In full-size trucks they’re just downright fragile late in life, and especially when they’ve been towed with. Great for S10s and mild B/F body cars, not so much for C/K trucks and Express/Savana vans, even less so with an even somewhat gutsy V8.

Very common to see them fail before 200K. My father has been particularly unlucky; his ’96 Z71 extended cab 4×4 has 275,000 miles, is still on the (very peppy) original engine, but just suffered the failure of its FOURTH tranny! Despite proper care and relatively gentle use, he has yet to get one that’s lasted more than three years.

Half-ton Suburbans all had them in the ’90s, and up into the early 2000s.

I held out for a 3/4 ton or bigger Suburban, since I tow (6000-8000lbs) frequently and therefore insist on a 4L80E. Those trannies are comparatively bullet-proof.

Of all the tranny swaps I’ve done in my adult life (at least a dozen), better than 2/3 have been 4L60Es. The 4L80Es, on the other hand, are much stouter – only ever had one of those begin to fail, in my former ’94 K2500 Suburban. Probably could have been saved (suspect bad solenoid), but rust was also a major factor… traded it straight-up for a Durango and a ’71 Ventura, to a guy who “had to have it!”.

Too bad PCM software differences prevent plug-and-play swapping of the two models. If I was equipped to re-flash those computers, I’d have upgraded at least two of my vehicles with ’80Es by now.

Turned out we’d both experienced these sorts of troubles, which gave him confirmation in resolving to check them carefully before any future purchase of a truck so equipped.


Then the conversation turned – exactly 90 degrees, in fact. He wanted to talk about GM’s transverse trannies; which were preferable, which were to be avoided.

FWD GM transmissions aren’t really my strong suit. I know they went through various revisions, but couldn’t list them all. Overdrive was added in the late eighties, electronic control in the early 90s, there were new designs to coincide with the Series II motors in the mid-90s, there were beefed-up versions to go with the supercharged motors, etc.

It’s not often that I find them dead or dying. But it seems like those which have been, could be split into two groups:


1) 4T60 hooked to an LN3. I don’t know whether it’s just coincidence, but I’ve seen several of them have issues at low miles, with no apparent reason for it. Noteworthy examples: a really nice ’92 Toronado with 120K and no third or fourth; and even my faux Touring Sedan, which has a mere 94K and has been guilty of hard downshifts and the occasional slippage under hard acceleration (fluid/filter change stopped the slipping, but didn’t completely resolve the hard shifts).


2) 4T65E-HD hooked to an L67. This one’s kind of a no-brainer: people drive their supercharged cars like it’s some combination of a NASCAR race and a stoplight drag contest, and the trannies won’t tolerate it. From low-mile Regal GSes with torque converter issues, to one particularly memorable GTP that had just broken 100K miles with the pump on its last leg, those trannies just weren’t quite HD enough for the lead-footed.


Other than those two examples, I see many others that just seem to go forever. Or rather, until someone pops a head gasket (especially 3.1/3.4), which is usually what seems to do these cars in.

But I’m no expert on the “wrong-way drive” cars, having owned mostly RWD vehicles – so having said my small piece, I now defer to the commentariat.

How about you? What’s been your experiences with the General’s transaxles?