72 Chevy K20 Transmission Swap?
 

I have a '72 K20 with the turbo 350 automatic transmission. I am just curious right now more than anything, but is there another transmission with possibly more gears that would fit in between the engine and the transfer case, without any major modification. I'm not willing at this point to move the engine or the transfer case. My goal is to improve fuel economy, just not smart enough on transmission to know what is swappable.

Re: 72 Chevy K20 Transmission Swap?
 

I think the answer is "no"

The 200-4R is direct swap for a TH350 2WD.

There is not a 4WD version of the 200-4R. The 700R4/4L60 are another option but are ~40mm longer

Re: 72 Chevy K20 Transmission Swap?
 

700R4 is an option but you need to move the motor ahead to the front set of holes in the frame.

Other option is buy a gearvendors over/underdrive and make your truck a 6spd but you have to shorten the rear driveshaft.

Re: 72 Chevy K20 Transmission Swap?
 

Any specific model of the 700r4 or are they all the same animal? Also wondering if it's as simple as moving to the forward set of holes? It fits with no further mods? Thanks Erik

Re: 72 Chevy K20 Transmission Swap?
 

Again me being ignorant about transmissions, but is it possible to get a six speed such as a 6L80 in there? Again looking at fuel economy as the primary drive for this line of question.

Merry Christmas.

Re: 72 Chevy K20 Transmission Swap?
 

I would go for the gear vendors setup if your budget allows that with the all ways reliable 350 turbo would last a good long time

Re: 72 Chevy K20 Transmission Swap?
 

you cant swap in anything that wont require modifications that will have an extra gear. if you are willing to go to the trouble of dealing with the electronics, i think a 6L would be fantastic. there are also valve bodies available that will turn the 4L80 into a 6 speed. that would be cool. i have an older 4l80e in my garage that i hope to do that with for something...

as far as swapping the trans, the easiest path would be the 700r4. i recommend moving the t-case backwards as opposed to the engine forward. it requires a modification of the drivelines, but i think it is better than moving the engine forward.

Re: 72 Chevy K20 Transmission Swap?
 

Would swapping the transmission for a 4 or 6 speed plus the gear vendor under/overdrive be overkill? Would I run into problems with too low of RPMs to keep the engine within proper temp? Would there be other problems that I could run into?

Re: 72 Chevy K20 Transmission Swap?
 

the advantage of the 6 speed is about the same as what you would get from keeping the three speed and adding a gear vendors. if you used the gear vendors with the 6 speed i dont think you would be very happy. the gear splits would be very fast and not much benifit for mileage. the double overdrive would keep the engine so far below its powerband that you would loose economy from it. you could use it as a splitter with a 4 speed but i still doubt it would benifit you much as far as economy goes.

Re: 72 Chevy K20 Transmission Swap?
 

Perfect, that is what I was thinking as well. Sounds like the best and easiest option would be just to add the gear vendor under/overdrive.

Re: 72 Chevy K20 Transmission Swap?
 

I swapped a th350 for 700r4 buy moving the engine forward. It was fairly easy. Only mod is drilling a couple new holes to move the engine forward. It is only moved like 3 inches forward, it is not noticeable and keeps the distributor away from the firewall for easier access, but Don't get a bigger trans pan. Front drive shaft wont work with it. I made that mistake.

Re: 72 Chevy K20 Transmission Swap?
 

How many different versions of the 700r4 are there? what did yours come out of, if you know? I like this idea of moving the engine forward. Did you still use the column shift linkage? or did you change this as well? thanks Erik

Re: 72 Chevy K20 Transmission Swap?
 

I do not know how many ,if any, different versions there is of the 700r4. The 700 i have came out of a 1987 c/10 and it needed a rebuild anyways so i had it rebuilt using the AA output shaft. The shift linkage fit without modifications. The only mod i had to do besides moving the engine forward is making a bracket next to the carb for the 700r4's kick down cable.