Trying to do the logical thing. - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ChevyRacefan · 01-20-2021, 01:18 PM

I look at it this way, your mileage may vary. BUT
When g.m. had Both a 350/th350 carb truck and a 350v8 /7004r carb truck.
The city mpg was the same and highway was 1 mpg difference.
So pick your poison .
The O/P already stuffed 3.73's in the rear, so at this point a 7004r might make sense, I think his math is suspect. His daily drive is not going to be all in 4th gear at a steady rate. So I think what he THINKS he will save in fuel cost, is um, well. you know.

James Lamb · 01-20-2021, 01:24 PM

Oops. I read it wrong. Yes, now has 3.73. I had the wrong way around. So yes, with a 3.73 diff it makes more sense. But I sure would not go to that kind of effort unless I was putting a lot of miles on it on a regular basis.

And if I was starting from scratch, or with the budget I have now, I certainly would not pick a 700r4. Too many better, more reliable choices.

72LB · 01-20-2021, 02:28 PM

Quote:

Originally Posted by James Lamb

And if I was starting from scratch, or with the budget I have now, I certainly would not pick a 700r4. Too many better, more reliable choices.

Do tell? I've gone thru a th350 and 2 th400's in mine that's why I'm looking to go 700r. If your suggesting a 4l60 they're scrap to begin with and I can't afford to rework a 4l80.

ChevyRacefan · 01-20-2021, 02:48 PM

Quote:

Originally Posted by 72LB

Do tell? I've gone thru a th350 and 2 th400's in mine that's why I'm looking to go 700r. If your suggesting a 4l60 they're scrap to begin with and I can't afford to rework a 4l80.

You do understand that a 4l60e IS the 7004r , only one is mechanically controlled and the other electronic sensors.
same guts, and internal parts.

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.

CC69Rat · 01-20-2021, 06:10 PM

LS.

SCOTI · 01-20-2021, 06:47 PM

Quote:

Originally Posted by CC69Rat

LS.

cj847 · 01-20-2021, 09:12 PM

Quote:

Originally Posted by CC69Rat

LS.

If I could trade my like new 350/350 combo for a 120k mile LS/4L60 I would definitely do that.

CC69Rat · 01-20-2021, 09:16 PM

I was kinda kidding, but just saying. For a fuel efficient driver you cant touch it with a carbed small block. The 700r will help, yes but I'm not sure I'd spend the cash to swap it. Tire size and of course shoe size matters too.

I like them all. I'm a BBC guy actually you just cant beat the LS for fuel economy. I'd save my 700r swap money and find a good 6.0 / 4L80.

With respect to the purists if that's your taste, go with it. Just my opinion.

siggyfreud · 01-21-2021, 12:13 PM

If you do go with a 700R4 check out TV-Made-Ez for Bowtie Overdrives. Their website sucks and half of it isn't working, but if you call them they're super helpful. I'm doing this swap currently just to make the highway manners better until I do my LT swap.

01-20-2021, 01:18 PM	#1
ChevyRacefan Registered User Join Date: Sep 2013 Location: Newton,N.C. Posts: 317	Re: Trying to do the logical thing. I look at it this way, your mileage may vary. BUT When g.m. had Both a 350/th350 carb truck and a 350v8 /7004r carb truck. The city mpg was the same and highway was 1 mpg difference. So pick your poison . The O/P already stuffed 3.73's in the rear, so at this point a 7004r might make sense, I think his math is suspect. His daily drive is not going to be all in 4th gear at a steady rate. So I think what he THINKS he will save in fuel cost, is um, well. you know.

01-20-2021, 01:24 PM	#2
James Lamb Registered User Join Date: Mar 2019 Location: Knoxville AL Posts: 74	Re: Trying to do the logical thing. Oops. I read it wrong. Yes, now has 3.73. I had the wrong way around. So yes, with a 3.73 diff it makes more sense. But I sure would not go to that kind of effort unless I was putting a lot of miles on it on a regular basis. And if I was starting from scratch, or with the budget I have now, I certainly would not pick a 700r4. Too many better, more reliable choices.

01-20-2021, 03:06 PM	#5
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.

01-20-2021, 06:10 PM	#6
CC69Rat Registered User Join Date: Jan 2011 Location: Chattanooga TN Posts: 6,208	Re: Trying to do the logical thing. LS. __________________ Chad 1967 C10 SWB - Project Savannah - 6.0/4L80 Currently underway 1968 C10 SWB - TOTY 2018, 50th Anniversary Tribute Project * Sold * Pride and Joy 1986 Silverado Short Fleet - Scarlet Sold 1985 Silverado Short Fleet Sold 2022 Jeep Gladiator Mojave 2001 Jeep Cherokee XJ 4x4 - Lifted, Built 1992 Jeep Cherokee XJ 4x4 - Lifted 2013 Honda Accord EX-L v6 Coupe 6spd (wife's ride)

01-20-2021, 09:16 PM	#9
CC69Rat Registered User Join Date: Jan 2011 Location: Chattanooga TN Posts: 6,208	Re: Trying to do the logical thing. I was kinda kidding, but just saying. For a fuel efficient driver you cant touch it with a carbed small block. The 700r will help, yes but I'm not sure I'd spend the cash to swap it. Tire size and of course shoe size matters too. I like them all. I'm a BBC guy actually you just cant beat the LS for fuel economy. I'd save my 700r swap money and find a good 6.0 / 4L80. With respect to the purists if that's your taste, go with it. Just my opinion. __________________ Chad 1967 C10 SWB - Project Savannah - 6.0/4L80 Currently underway 1968 C10 SWB - TOTY 2018, 50th Anniversary Tribute Project * Sold * Pride and Joy 1986 Silverado Short Fleet - Scarlet Sold 1985 Silverado Short Fleet Sold 2022 Jeep Gladiator Mojave 2001 Jeep Cherokee XJ 4x4 - Lifted, Built 1992 Jeep Cherokee XJ 4x4 - Lifted 2013 Honda Accord EX-L v6 Coupe 6spd (wife's ride)

01-21-2021, 12:13 PM	#10
siggyfreud Registered User Join Date: Jun 2012 Location: Portland Posts: 1,330	Re: Trying to do the logical thing. If you do go with a 700R4 check out TV-Made-Ez for Bowtie Overdrives. Their website sucks and half of it isn't working, but if you call them they're super helpful. I'm doing this swap currently just to make the highway manners better until I do my LT swap. __________________ Current Build - Project "Ghost of Poseidon" 72 C10 Pro-touring build Previous Build - 66 GMC Pro-touring build. Sold.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.