4L60 to Replace TH350?
Thread Starter
Racer
Joined: Apr 2011
Posts: 254
Likes: 0
From: Great Falls MT
4L60 to Replace TH350?
I have two questions. On my 79', is it possible to replace my Th350 with a 4L60? My engine is NOT original (serial numbers don't match), so would this hurt my cars value?
I happen to have the 4l60 Tranny and am looking for ways to improve gas mileage on an otherwise great car. One thing I have to admit: it has a 4:10 rear end and I know I have to replace that, so I'm also looking for someone who likes to get off the line fairly fast who might want to trade.
I happen to have the 4l60 Tranny and am looking for ways to improve gas mileage on an otherwise great car. One thing I have to admit: it has a 4:10 rear end and I know I have to replace that, so I'm also looking for someone who likes to get off the line fairly fast who might want to trade.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
For those who want an original car, everything they have to return to normal is going to hurt the value.
For those who want a nice driving car, it may help... really depends on the buyer.
I'd do the 4L60 first if you're really keen on that transmission, and see how the 4.10s feel after that. Have you tried driving a car with the 4L60 transmission to see how you like the shift points?
For those who want a nice driving car, it may help... really depends on the buyer.
I'd do the 4L60 first if you're really keen on that transmission, and see how the 4.10s feel after that. Have you tried driving a car with the 4L60 transmission to see how you like the shift points?
Pro
Joined: Apr 2007
Posts: 528
Likes: 9
From: Grand Rapids Michigan
I don't know what the gear ratios of the 4L60 are, but I think it is an electronically controlled tranny... and that will be a difficult swap in your not computer controlled car.
The 700R4 and 2004R are the two used most often.
Maybe you can trade your core 4L60 for one of those.
The 700R4 and 2004R are the two used most often.
Maybe you can trade your core 4L60 for one of those.
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
I'd do the 4L60 in a heart beat, but going to be one heck of a first gear with a 4.11 axle. 700R4/4L60's have a 3.05 1st vs TH350 2.50 1st, so figure a 12.5 1st ratio at the wheels. Even with 4.11 axle, the 4L60's 4th 0.70 o.d. will yield an equivalent 2.88 cruising ratio + lock up converter, and probably be fine. The non "E" 4L60's really just an upgraded 700R4, and is a fairly simple install. If doing it again, probably go with the "E" model and computer, as much easier to dial in shift points.
Thread Starter
Racer
Joined: Apr 2011
Posts: 254
Likes: 0
From: Great Falls MT
The only 4L60 I've driven was an E model in a Tahoe. Not a good comparison. I've just been thinking of replacing the 4.10 (4.11?) rear end with something like a 3.08 when I remembered the 4L60 in storage. I love to drive this car, but at 10mpg I don't drive it far. On the highway at 70mph I'm turning 3500rpms. In the late 60s I had a 55 Chevy with a 4.55 positraction that was the same. But then gas was 30-35 cents a gallon! I guess I'd probably be better off swapping the rear end and keeping the car as stock as possible. There is nothing wrong with the rear end I have, so if anyone knows of a trade I'd be interested.
Le Mans Master
Joined: Feb 2011
Posts: 5,943
Likes: 61
From: Southern NH
A 4L60 is a 700R4, Gm went to a universal system of naming transmissions is the 90s, so the name was changed. If its a 4L60E then its electronically controlled, but there are modules you can buy to make them work.
I have a 4L65E in my Silverado (same as a 4L60E but with stronger planetary gears and a hardened output shaft) with a shift kit. I'm running 4.11s and 31" tires and I love it.
I have a 4L65E in my Silverado (same as a 4L60E but with stronger planetary gears and a hardened output shaft) with a shift kit. I'm running 4.11s and 31" tires and I love it.
Instructor
Joined: Apr 2011
Posts: 151
Likes: 1
From: Cedar Springs MI
A 4L60 is a 700R4, Gm went to a universal system of naming transmissions is the 90s, so the name was changed. If its a 4L60E then its electronically controlled, but there are modules you can buy to make them work.
I have a 4L65E in my Silverado (same as a 4L60E but with stronger planetary gears and a hardened output shaft) with a shift kit. I'm running 4.11s and 31" tires and I love it.
I have a 4L65E in my Silverado (same as a 4L60E but with stronger planetary gears and a hardened output shaft) with a shift kit. I'm running 4.11s and 31" tires and I love it.
