# hydo400 or 700r4????



## DWittenbreder (Nov 8, 2009)

I bought a 90 3500 4x4 w/ turbo 400...4.56 gears. truck was screaming @ 65 on the way home...I have a good 700r4(rebuilt by a reputable shop) I just don't trust them as I know the 400 is built up by previous owner but I really could use the OD on the highway. I'll be haulin' wood, towing a 35' camper, and using as a daily driver. What do you guys think???


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## spacemule (Nov 9, 2009)

I think the 400 is a stronger design that is suitable for high horsepower. With a 454, you aren't going to get good mileage no matter what gearbox you have.

Er, I assume you have a 454.


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## wigglesworth (Nov 9, 2009)

The 700 would probably be fine, but the 400 is one tough bird. Are you sure on the gearing? If so, i would suggest changing the gearing as opposed to the tranny. That is way low geared, but I bet there isnt anything it wont pull.


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## s13rymos (Nov 9, 2009)

Put the 700r4 in..Make sure you have a deep pan and a big cooler to keep the temps down.. it should last..


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## wigglesworth (Nov 9, 2009)

another point....the 700 has a lot lower 1st gear than the 400. Talk about a stump puller....


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## Den69RS96 (Nov 10, 2009)

The 700R4 is a turbo 350 with overdrive. They can be built to hold alot of hp, however, the turbo 400 is pretty strong right off the bat.


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## barneyrb (Nov 10, 2009)

Turbo 400 + http://www.gearvendors.com/4x4gm.html = bulletproof


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## boostnut (Nov 10, 2009)

Den69RS96 said:


> The 700R4 is a turbo 350 with overdrive. They can be built to hold alot of hp, however, the turbo 400 is pretty strong right off the bat.



Whaaaa? You ever tear into these 2? You make it sound so simple. The 700R4 is a pita, a th350 can be rebuilt by most tranny guys left handed and blindfolded.

Back to the OP's issue. I'd run the 700. A buddy of mine has a farm truck thats an early 90's GMC 3/4 ton 4x4 diesel w/15x,xxx miles of pure abuse. Tranny has never been touched aside from fluid/filter changes. Also, we've got an early 90's 3/4 ton diesel suburban at my shop with about the same mileage. Once again, tranny has never been touched. If they'll live behind the torque of a diesel for that long than I've gotta say the decision is easy. As mentioned above, keep it cool! An external cooler is not an option, but a requirement. I'd have a temp gauge in it too.


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## chowdozer (Nov 10, 2009)

The Turbo 400 eats up an additional 30 hp over the 700R4. But then I don't think anyone really knows the limits of a Turbo 400 either. If you swap you'll probably be looking at another transfer case and drivelines. It really depends on how many 60mph miles you'll be putting on it.


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## sawinredneck (Nov 10, 2009)

I hate, loath, and flat out despise the 700R4 tranny! I went through six of them in my Suburban. Rebuilt by this pro shop or that pro shop, junked them all in six months! I special ordered one from this place in Cali (many moons ago) and three months later I got a box large enough to be a tourqe converter:monkey: I refused to accept it and finally got my money back, I think they are out of buisness now.
I keep hearing they can be built to hold horsepower, maybe, but I know they sure didn't like towing and off roading, kicked out of OD when doing both.
I spent two hours on the phone with one builder trying to talk him into putting in a 400 for me, he insited a 350 with a lockup converter was the ticket, it lasted just over a year. I don't like them!!! Just teling my experiance with them.
I would look and see about droping in the 4R8 or whatever the number is on the new heavy duty tranny Chevy has out, I've nothing but good things about it, and they make a kit so it can run as a stand alone. Yeah it's expensive at first, but figure $900-$1400 times six, it's cheap then aint it?
Also, unless you are runnin 38" or bigger tires, I'd drop the gear ratio, a 3:73 or 4:10 wont be that noticable in towing, but help the mileage quite a bit! I was running 3:42's with 33" tires and had plenty of power with a built Small block 400.


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## carpenter383 (Jan 22, 2010)

Heat is the enemy of any trans. 700's can be built to handle quite a bit of power, but it needs a .500 boost valve extra 3/4 clutches a good input sprag and a beast sunshell before I would trust it for heavy hauling/towing. 
The first trans I ever rebuilt is a 700r4 which was 7 yrs ago and it will still bark 2nd and 3rd on street tires, it's in the monte in my signature which runs 7.80's in the 1/8th on slicks.
Ideally you need a 4l80e these are a th 400 with overdrive. The only prob is they are all electronic so the easiest thing would be to buy a kit to convert it to vacuume controlled shifting. BUT you could buy alot of gas for what you'd have in one


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## funky sawman (Jan 22, 2010)

Build a 700r4 and get a advanced adapters kit to mount the 700r4 to the 205 t-case, I thank you need to have the driveline lengths modifyed though. I did that to a buddys 1982 k3500 dually crew cab with 35" tires and it had a supercharged 468 BBC running 9 psi boost and he uses it to haul a boat, never had any problems with it.(going on 55,000 miles now)


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