[MonkeyMuscles]

I was looking at a K20 6.2 truck that was most likely a mid to late 80's style at a junkyard today. The guy said it was for sale as a whole and not a parts truck but just say I might be slightly interested I was just curious what automatic transmissions they put in those trucks? I know the TH700 is basically a 4L60 and wasn't usually considered a strong transmission which I would think came mainly in the light duty trucks but is the TH400 as strong as so many people make it out to be? I also understand the TH400 is just a 3 speed to which would result in less highway fuel mileage. I am curious which transmission most likely came in this truck because I don't really like automatic transmissions in a truck unless it's an Allison but the 6.2 doesn't have that much power anway.

 

[bowtie]

If they had 4 speeds then it most likely is the 700r4, which isn't a bad tranny just keep it cool. I loved mine and 4 wheeled it all the time. I believe there was a 4L80 no "E" that was used too.

 

[Boostmonkey]

I have a 700 in my '69 and that makes alot more power than a 6.2, just make sure it is built right and put a big cooler on it and you should have no problems. I dont tow anything with it, but with that much power and 16" wide slicks I have over 4000 trouble free miles. Another good thing is the gearing, 1st is 3.06:1 and a .7:1 overdrive helps with milage even withe the 4.10 rear.

Rob

 

[maulcruiser]

TH-700's got a bad rap when they first came out. GM revised them, and they hold up fine, but the image was already tarnished. I personally ran one in my 90 K5, with a warmed over 350 turning 35" tires. The stock tranny lasted to 143K, but my dad killed it towing a loaded trailer that probably weighed more than the Jimmy itself. After rebuilding, I hammered on it for 4 more years, then parted the truck out. Last I heard, the current owner still has it, and drives it just as hard as I did. I parted the truck out 3 years ago...

So IMHO, go with the 700, and like Rob said, put the biggest cooler on it you can find. It's cheap insurance.

 

[JRKRACE]

IIRC, that truck came with a Turbo 400. Easy way to tell is if it's a 3 or 4 speed auto. I,m pretty sure it's a three speed.

 

[High Sierra 2500]

I,m pretty sure it's a three speed.

Not necessarily. The 3/4 ton trucks were available with the TH700R4. Look at my sig...

Anyhow, I like my 700R4. The overdrive and the lockout converter really help with fuel economy. I don't like the tendency to down shift on hills when I'm towing or have a heavy load in the bed. Other than that I have no complaints. My tranny is a little funky due to age, never having a fluid change in its entire life, and sitting for several years, but it is settling down nicely as I run it more. It seems to have held up well to a very rough life as a steel company work truck (used for some VERY heavy loads in the bed), and as a farm truck (has seen its fair share of rough towing with heavy loads), followed by its current occupation as a daily driver with occasional loaded runs and towing.

 

[MonkeyMuscles]

Thanks for the feedback everyone. The only reason I thought the 700 was a weak transmission is because of 4L60-E's rep. in the 94-96 Caprice/Impala. Seems like some will last 150K and still shift fine while others are fried in under 100K miles. With that in mind I didn't like the idea of one in a truck with 4WD but I guess there must be some kind of a difference.

 

[TFLundyB275]

could be either tranny. first year 700R4's where troublesome no doubt. quality rebuilds can be done and have a stronger result. like said before a cooler is a must for this tranny.

 

[bowtie]

Correct, early 700's were a PITA, but as updates went in and rebuilders learn how, and oh course the public was make aware of how to they became much more dependable. I had one in my "baby", a 82 K1500 6.2 that stood 8 foot and would go about anywhere I pointed her in Alaska. I love the 700R4 behind the 6.2 because of the 3.08 first gear for grunting and overdrive for cruising. Treat her right and she be there for the long haul.

 

[Jake]

My experience with the 700R4 in an 83 Suburban w/6.2 was not the best. I towed occasionally, but not in OD. My first transmission got me to 195K. I towed a 13,000# boat about 4K of those miles (two long moves). After being rebuilt, it lasted 60K. Another rebuild kept it going until we parted company at 275K. I kept an auxilliary cooler on it, but wasn't monitoring the transmission temps like I do now.

I would recommend a turbo 400 over the 700R4, but then the 400 doesn't have overdrive. Tough choice I guess.

Jake