Quote:
Originally Posted by custom10nut
I’m beginning to consider changing out my TH350 trans for one of the Following.
1.700R4
2. 4L60
3.4L80
What are the Pros/Cons of each, in regards to Electronic Wiring and reworking, Trans Tunnel clearance or modifications required, Crossmember mods, and Driveshaft requirements.
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- 700R4
This transmission is one of the easiest to convert. Requires moving the cross-member slightly to the rear and a shorter driveline. Use a 1987 to 1992 transmission for the best service. The 350's cooler lines can be reused with just a slight tweaking. Most of these transmissions have an analog speedometer output that can be used to run the factory speedometer in the C10's. All that is required is the plastic gearing with the correct ratio.
- 4L60
This is the 4L60E I am assuming. Requires a computer to shift. If you are transplanting an electronic injected motor this is the way to go. You can run into issues getting the flex plate to torque converter spacing correct. Computer will run the lock up so no issues there. Since this is the same physical dimensions as a 700R4 (up to 2000) it requires moving the cross-member slightly to the rear and a shorter driveline. The 350's cooler lines can be reused with just a slight tweaking and adapting the snap in fittings if it has them. Adapting an analog speedometer can be interesting. Many only have provisions for electronic sensors. Especially true of the 2001 up 4L60E and 4L65E with the 6 bolt tail housings.
- 4L80
Installing a 4l80 requires moving the cross-member to the rear. Also required are different transmission lines, a modified or swap harness with computer and associated inputs, and a modified driveshaft with a larger yoke and crossover U-joint. Otherwise, the stock shifter will still work and the factory ECM can control all of the 4L80E's functions.
The torque capacity of the 700R4/4l60E's are relatively close to the 350's and the 4L80E similar to the 400's. You didn't ask about the 2004R. It is a direct bolt in for the THM350. Same length, same cooler lines and output shaft spline count. Getting difficult to find and does not have the strength of the other transmissions. Upgrading a 2004R costs more than just using a 700R4.