#4l60

We return to the Turbo-Hydramatic once more today, and our third installment sees us at a critical point in the timeline of the automatic transmission. Fuel economy pressure from the government and performance demands of the consumer increased considerably in the intervening years since the THM’s debut in 1964. That meant the creation of lighter, more compact, and cheaper versions of the Turbo-Hydramatic compared to its flagship shifter, the THM400. GM branched out into the likes of the THM350, THM250, and the very problematic THM200.

In 1987, GM stepped away from the traditional THM naming scheme and switched to a new combination of letters and numbers. Number of gears, layout, and strength combined to turn the THM400 into the 3L80. But the hefty gearbox was already limited by then to heavier truck applications; passenger cars moved on to four forward gears after the dawn of the Eighties.

TTAC commentator SavageATL writes:

I have a 1991 Cadillac Brougham, the old rear-wheel-drive model. The car was sitting for a long time, and it has a Chevy 305 with bad valve seals. Lesson: beware of low-low-mileage cars.

It smokes badly on startup after sitting and burns a good bit of oil — about one quart every 250 miles. I’ve driven it as-is for a while, but the day is coming when I’ll need to do something about it.

I was told that the heads would need to be replaced to the tune of about $800. I am thinking for that kind of money I can go ahead and swap out the 305 for an LS. I was quoted about $2,750 for a 5.3-liter junkyard LS swap and $3,750 for a 6.0-liter junkyard LS swap, start to finish.

TTAC Commentator anti121hero writes:

Hello Sajeev! Very long time reader, but first time I’ve ever reached out. To start, I happen to be a huge RWD ford fan, (I’m actually helping my best friend put together his 94 mark viii). Now with your interest gained…