Th400/NP208 to 700R4/NP208 Conversion V2500 Suburban

[350runner]

I'm considering a 700r4 real hard for my C20 with 454. Mostly just for experimental or R&D purposes. Break it, Disect it and make it better til I get one that one that holds up to abuse. And I have full intention of towing in overdrive too. I will be using billet superhold 3/4 Servos though. That will hold the OD clutch pack tighter, less slippage = less heat. I'll also be using the Commercial Alto 3/4 clutch pack. Not the OEM pack or the Raysbestos Z pak.

This really sounds like a good game plan I plan to do the same thing. Today hauled a payload to the scrap yard just got grins. It shifted smooth as butter... didn't get hot like it did with the th350. Road out there in od 24 miles lil stop n go mostly 65 mph.

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[HotRodPC]

This really sounds like a good game plan I plan to do the same thing. Today hauled a payload to the scrap yard just got grins. It shifted smooth as butter... didn't get hot like it did with the th350. Road out there in od 24 miles lil stop n go mostly 65 mph.

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By all rights, the 700r4 should run much cooler than any Th350 or Th400. And they need to. The thing to keep in mind about 700r4's is no matter how much you do to them, they will NEVER hold up to the abuse a Th400 will and a Th350 in some aspects. You can modify the clutch packs and update servos all you want, but at the end of the day, they still have smaller shafts, more sealing rings that create weak spots in the shafts, as well as an aluminum pump body and valve body vs cast iron, and vane pump instead of iron crescent gears. Those aluminum bores and bodies wear much quicker than the iron does. And those aluminum bodies are overlooked during rebuilds too.

 

[350runner]

By all rights, the 700r4 should run much cooler than any Th350 or Th400. And they need to. The thing to keep in mind about 700r4's is no matter how much you do to them, they will NEVER hold up to the abuse a Th400 will and a Th350 in some aspects. You can modify the clutch packs and update servos all you want, but at the end of the day, they still have smaller shafts, more sealing rings that create weak spots in the shafts, as well as an aluminum pump body and valve body vs cast iron, and vane pump instead of iron crescent gears. Those aluminum bores and bodies wear much quicker than the iron does. And those aluminum bodies are overlooked during rebuilds too.

Oh yea no doubt there's no kinda dispute there. But that od and lock up tho... if one used the trans for daily commute it would hold it's own.

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[v2500burb]

Let me know what y'all think


700R4 Transmission Super Duty 4WD 4x4
View/Hide options
Torque Converter: 1650 Stall, with Lockup - $145.00
Shift Firmness: Level 2, Firm positive shifts (most popular!)
Case Type: 4 Bolt Truck Case
Lockup: 4th Gear External Lockup Kit (Recommended if you are converting to a 700R4) - $95.00
Pan Style: Chrome Pan, Stock Depth, with drain plug
Valvebody: Automatic/Manual with Constant Pressure Modifications - $99.00
Warranty: 90 Day, Unlimited Mileage
Popular Accessories (These have been Discounted for your transmission package!): TV / Throttle Cable $35.00
Chrome TV Cable Bracket $19.95
Locking Fillertube & Dipstick $35.00
Torque Converter Bolts (3) $9.99
Universal Dust Cover $25.00



Subtotal $2,154.27
Extra 10% Discount $202.93
TOTAL $1,951.34


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[350runner]

For that cost just get a trans from monster transmission online.

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[350runner]

Just joking... but there really isn't much in the way of performance up grades there. Like the 3/4 clutch packs. Servo up grade and such like hr spoke of. I'd follow hr with his advice.

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[350runner]

Here is a thread regarding someone looking into their upgrades http://www.pirate4x4.com/forum/chevy/855687-700r4-trans-rebuild-heavy-duty-parts-kit-not.html

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[350runner]

Here is cheaper better built 700r4 https://www.monstertransmission.com/mobile/home.asp#page-103

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Link doesn't work to the trans I was trying to link it to, but Its the one rated for 500 hp 4x4

 

[v2500burb]

It seemed a BIT steep



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[350runner]

This is a great site to read from. http://www.transmissioncenter.net/competition.htm

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[350runner]

This is where I would suggest getting a trans from. They list the parts used and why very good read http://www.transmissioncenter.net/performance_automotive.htm

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[v2500burb]

Now my mind is rolling.... Maybe a rebuild in my basement
Might be a good winter project....


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[350runner]

Yup you could build one just like theirs

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[HotRodPC]

Let me know what y'all think


700R4 Transmission Super Duty 4WD 4x4
View/Hide options
Torque Converter: 1650 Stall, with Lockup - $145.00
Shift Firmness: Level 2, Firm positive shifts (most popular!)
Case Type: 4 Bolt Truck Case
Lockup: 4th Gear External Lockup Kit (Recommended if you are converting to a 700R4) - $95.00
Pan Style: Chrome Pan, Stock Depth, with drain plug
Valvebody: Automatic/Manual with Constant Pressure Modifications - $99.00
Warranty: 90 Day, Unlimited Mileage
Popular Accessories (These have been Discounted for your transmission package!): TV / Throttle Cable $35.00
Chrome TV Cable Bracket $19.95
Locking Fillertube & Dipstick $35.00
Torque Converter Bolts (3) $9.99
Universal Dust Cover $25.00



Subtotal $2,154.27
Extra 10% Discount $202.93
TOTAL $1,951.34


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For that price, IMO, that's ****** warranty. 90 days???? I'd give 90's days on a basic 'just replace what it needs" build. Even Jasper gives a 3 year or 100,000 mile warranty.

 

[350runner]

Yea for the kinda money you were quoted I'd suggest getting a level 4 or three trans from the transmission center link I posted. Our try building on like theirs, but by the time you add up parts and tools you'll be over their cost for one shipped. That's why I just had one built

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