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James Lamb · 01-20-2021, 03:06 PM

I am certainly no expert on transmissions, so I should qualify that I'm basing this off personal experience. And my experience with 700r4 transmissions has not been good. I did have one built by a custom shop with upgraded internals that worked great right up until it didn't, at about 80,000 miles. That same shop built another one that lasted 1000 miles. They are extremely finicky, want the cable adjusted very precisely or will grenade on you. I have also found not many places that seem to know what to do with one. If you ask 3 transmission shops the same set of "test" questions and get 3 different answers, it does not inspire confidence. I think partly this is due to the age of the design, and a dwindling pool of transmission shops with direct experience with them.

My most recent venture, to get the truck running again, I found a retired guy who built me one, seems to be OK. Even at that, 500 miles later I had to replace the new lock up solenoid because the part was just bad from day one. My cam/carb/intake set up seems to not make enough vacuum for the vacuum switch to work, so at the moment I have the lockup switch wired for manual control while I wait on an adjustable vacuum switch to arrive.

Again, no expert, but I have had a couple of people say the late 4l60e is the one to go after, i.e one from about 1999 to 2000. The major advantage there being dropping the finicky cable adjustment, letting the ecu shift and not worry about amount of vacuum, etc.

I misread your early post about diff gearing. If you are driving highway speeds a 3.73 gearing would probably benefit from overdrive. Just can't say I recommend a 700r4. For the hassle if you are only using 10 gallons a week it will take a long time to benefit from extra fuel economy. That being said, I myself find it a sort of personal affront to not get the best mpg I can, no matter what car I am driving, so I get it.

Best of luck.

01-20-2021, 03:06 PM	#22
James Lamb Registered User Join Date: Mar 2019 Location: Knoxville AL Posts: 74	Re: Trying to do the logical thing. I am certainly no expert on transmissions, so I should qualify that I'm basing this off personal experience. And my experience with 700r4 transmissions has not been good. I did have one built by a custom shop with upgraded internals that worked great right up until it didn't, at about 80,000 miles. That same shop built another one that lasted 1000 miles. They are extremely finicky, want the cable adjusted very precisely or will grenade on you. I have also found not many places that seem to know what to do with one. If you ask 3 transmission shops the same set of "test" questions and get 3 different answers, it does not inspire confidence. I think partly this is due to the age of the design, and a dwindling pool of transmission shops with direct experience with them. My most recent venture, to get the truck running again, I found a retired guy who built me one, seems to be OK. Even at that, 500 miles later I had to replace the new lock up solenoid because the part was just bad from day one. My cam/carb/intake set up seems to not make enough vacuum for the vacuum switch to work, so at the moment I have the lockup switch wired for manual control while I wait on an adjustable vacuum switch to arrive. Again, no expert, but I have had a couple of people say the late 4l60e is the one to go after, i.e one from about 1999 to 2000. The major advantage there being dropping the finicky cable adjustment, letting the ecu shift and not worry about amount of vacuum, etc. I misread your early post about diff gearing. If you are driving highway speeds a 3.73 gearing would probably benefit from overdrive. Just can't say I recommend a 700r4. For the hassle if you are only using 10 gallons a week it will take a long time to benefit from extra fuel economy. That being said, I myself find it a sort of personal affront to not get the best mpg I can, no matter what car I am driving, so I get it. Best of luck.