BB, 700R4 and 3:08's

[Already Gone]

Is anyone running the combo of Big Block with a 700R4 and 3:08's on a C10. I'm curious as to driveabily, power and fuel economy.

[Bigdav160]

I had a '67 swb with a 402 and a 700R4.

Although my axle ratio was 3.73:1

Ran great. But I don't think a 700R4 (even with mods) is much of a match for the torque of a big block. It'll break eventually.

[Already Gone]

ttt
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[Fitz]

Originally Posted by Already Gone

Is anyone running the combo of Big Block with a 700R4 and 3:08's on a C10. I'm curious as to driveabily, power and fuel economy.

A 700R4 will not take the torque of a big block. Very bad idea and expensive when you break it which you most certainly will..

[cwilkie]

I had that same setup. I had to be going over 60mph for overdrive to kick in. I loved the lower 1st gear. In the end I went back to a th400 and kept the 3.08 gears. I would not put a 700r4 in with a gear ratio that high again.
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[Lee H]

From what I've read 3:08s in OD put the motor well below the optimum power range causing the engine to work harder, use extra gas, and cause the trans to hunt way to much. I don't know what the best gear to use is but have read 3:73s work nicely. I've done enough research that I will use 3:73s when I go with an OD trans.
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[Already Gone]

Originally Posted by Fitz

A 700R4 will not take the torque of a big block. Very bad idea and expensive when you break it which you most certainly will..

I have heard that before and yet I wonder how the 700r4 stood up to the the 454 in the 80' and early 90's that were in 3/4 ton pickups, Suburbans etc. Although I have a 396 in my truck I dont race or blast away from stop lights.
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[Already Gone]

Originally Posted by cwilkie

I had that same setup. I had to be going over 60mph for overdrive to kick in. I loved the lower 1st gear. In the end I went back to a th400 and kept the 3.08 gears. I would not put a 700r4 in with a gear ratio that high again.
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Thanks for the info.
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[Longhorn 70]

TCI 700R4
The RIGHT 700 will handle big blocks. I broke many TH400s and my 700r4 has been going since 97. Most of that time my built Olds BB was abusing it.
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[425HP409]

I believe that 3.73s are the optimum gear to run with a 700r4 or other overdrive transmission. I am running them in two trucks with great success. The 700R4 will handle 450 HP if built right with some upgrades. I have been running one in my 454/425 HP Sprint for 20 years, hard driving, racing, and cruising. I built it with a HD converter, Kevlar band, a 9 clutch 3-4 clutch pack, Corvette Servo, a .500" boost valve and a shift kit. It shifts nice and smooth on light throttle, and will bark the tires on the 1-2 shift on medium to hard throttle.
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[Bigdav160]

I have heard that before and yet I wonder how the 700r4 stood up to the the 454 in the 80' and early 90's that were in 3/4 ton pickups, Suburbans etc

I can't say I've ever seen one. And I was a transmission tech at the Chevy dealer during that time. I only remember TH400 and 4L80e behind 454's.

GM did put the 700R4 behind the 6.2L diesels. They broke.

[Already Gone]

Originally Posted by Bigdav160

I can't say I've ever seen one. And I was a transmission tech at the Chevy dealer during that time. I only remember TH400 and 4L80e behind 454's.

GM did put the 700R4 behind the 6.2L diesels. They broke.

I was just assuming that the 80's - 90's vehicles had the 700R's
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[Fitz]

Originally Posted by Already Gone

I have heard that before and yet I wonder how the 700r4 stood up to the the 454 in the 80' and early 90's that were in 3/4 ton pickups, Suburbans etc. Although I have a 396 in my truck I dont race or blast away from stop lights.
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The most powerful variant of the motor you point to had these specs:
340 hp (254 kW) @ 4200 RPM 455 lb·ft (617 N·m) @ 3200 RPM. The
4L60 and the 700R4 have the same torque specs: 360 ft lbs max.
Pretty anemic numbers for a 454. Everybody thinks the more modern 454 engines developed the power of an LS6 (450 hp 505 ft lb of torque), but they don't. Not by a long shot.

While it is true you can build a 700R4 to take higher levels of power, these transmissions are only good for 150 passes or so on the strip before they need rebuilding. And that's a 1300.00 rebuild IF the case is still good. How do I know that? I went all through this argument when I was building my truck and, fortunately, I had an expert living right down the street. Johnny Winters. No, not the 60's and 70's rock star but the man behind JW Performance. He helped me after I turned two 700 R4's
into grenades. He set me straight with a built Turbo 400.
My JW built turbo 400 with manual valve body and 7 inch sprags will take 1000 HP and 1200 Ft Lbs of torque. Backed up with a Gear Vendors overdrive the engine ticks over at 2300 RPM at 75 on the expressway here in Tucson.

200 Passes at Southwest International dragway and 15,000 street miles without a failure. Not one. So, use your 700R4's behind those 454's. if you ever get stranded on the side of the road here in Tucson I'll give you a tow to the nearest AAMCO transmission shop!

[Fitz]

Originally Posted by Bigdav160

I can't say I've ever seen one. And I was a transmission tech at the Chevy dealer during that time. I only remember TH400 and 4L80e behind 454's.

GM did put the 700R4 behind the 6.2L diesels. They broke.

They parked all those 700R4 trucks way off in the back of the lot...right next to the Unicorn paddock.