700r4 or 400 turbo

[scot5146]

hey guys-

OK so bare with me... i am new to diesels and just bought my first 6.2 L 1987 suburban!

The rig runs great but I have a few questions, I have a big lift and 36" tall tires that I am going to put on the rig...

Is the 700r4 going to hold up or should I switch to a 400 turbo, I have a 3:73 gear ratio in the rear end and I am trying to figure out what transmission will turn the tires the best and hold up against a modified 6.2L.

Again bare with me I am learning as I go... Thanks for any help! Oh and I read Jims 6.2L volume 1 (very helpful)

Thanks again
Mike

[Crank Shaft]

I do not like the 700r4 for anything , i have a small pile of them out back all dead , if you want to spend a lot of money , they can be built up some. Tb 400 and the Tb 475 very strong units but no overdrive. Go with the 4L80E for overdrive and get a non lock up converter or the electric bypass set up from painless, . Just my thought on it

[Crank Shaft]

http://www.chevyhiperformance.com/techarticles/60978_transmission_swapping_tech/index.html

http://www.rowand.net/shop/tech/automaticoverdrivetransmissionswap.htm

Just some info . Maybe not as easy as i thought , the tb 400 will hold up better than the 700r4 and dont forget a cooler heat kills them quick.

[JeepSJ]

You can't beat an overdrive for mileage! I love my 700R4. They can easily be built to take the power of a diesel and live a long life. They don't suck as much hp as a 400 either. Running a 4L80E will require a controller for the trans.

If you have a 1500, those 36's will kill that stock rear end in a very short time and probably snap axles too. You probably want to run at least a 4.11 gear with those tires.

[DmaxMaverick]

4.10 gears with a turbo, 4.56 gears N/A. If you don't, you will be sorely lacking power, and your mileage will (regardless of the tranny) be about 25% less (highway, using the highest gear it will hold). Very true about the axles. Either a FF (3/4 or 1 ton axle), or late 1970's 12 bolt rear end will hold up to it. With 3.73 gears and 36" tires, you will have little usable power, very poor mileage, and likely destroy the drivetrain, torque converter to axles. If you use 4-low, the OEM 10-bolt axles will twist like spaghetti, right before the carrier and R&P launch out the new gaping hole in the diff cover (ask me how I know this).

Either tranny will work, provided they are properly built. The 700 has a significantly lower 1st gear than the 400 (VERY beneficial with a low power engine and very tall drivetrain), and the OD. A good aftermarket HD lockup converter is a bonus. Otherwise, switch to a full time open converter (different animals, DO NOT try to run the lockup converter as a full time open). Mileage and the ability to keep the engine in the power band is greatly enhanced with a lockup, and they will help with highway mileage. Any way you go, absolutely max out the tranny cooling system (large cooler up front). A 4L80 would work, but will cost an arm and a leg more, is a lot more complicated, and the parasitic loss is greater (robs power and economy). They do work very nicely when properly setup with a stand-alone controller, though. If you use a 400, you will need a vacuum pump/system. The 700 and 4L80 don't require vacuum. If you need the vacuum for HVAC controls anyway, the vacuum issue may be moot (although you will need a vac valve on the injection pump).

[scot5146]

OK so what if I change the axles to a Dana 60 front and corporate 14 rear, I can get access to a set for real cheap from a friend of mine...

They are 4:10 ratio, so If i rebuild the 700r4 with a really good rebuild kit then I should according to what you guys are saying, have a pretty good combo? :confused:

I really don't want to mess with the 4l80E because it looks like more of a problem then a solution, I don't know much about electrical and its expensive to have it hooked up...

So in the opinion of the experts "YOU GUYS" a 700r4 with 4:10 heavy duty axles should be a good combo?

Also what kind of torque converter should I use with a good rebuild?

thanks again

Mike

[DmaxMaverick]

That will work. Good combo. Robyn can tell you how to build that 700 to handle anything you can throw at it. A simple "kit" won't do it. There are some hard parts needing upgraded. She'll be along, I'm sure. She'll probably try talking you into the 400, so take it for what it's worth. I've done some really good 700's, but she's more up on recent stuff.

4.10 gears will leave you wanting for power. The 700 will make up for some of it, with the lower early gears, but OD will be almost unusable. 4.56 gears with 36" tires and a N/A engine will work well. Older military rigs use this with the TH400, but they max out at about 60 MPH with no OD. A gear ratio change isn't so bad, especially with the Dana and GMC diffs (easy, and not too expensive).

One significant advantage of the N/A 6.2 is the torque around the torque converter stall speed. The 6.5TD (and even the Duramax) can't match it. That's what kills diffs, axles and trannies when crawling around at low speed in low gears. A turbo is excess baggage until it spools up. My '85 with 4.10, 700R4 and 33's will out-crawl and out-torque them, all at barely off idle (and get 25+ MPG all the way home). It's all relative to what you want to do with it.

[scot5146]

"What I want to do with it"?

well at most I am thinking about pulling a ski boat and a 6x12 dual axle trailer during firewood season... I would like to keep the fuel economy the best I can with the large tires, I know I am not looking for a hotrod diesel, just a strong and reliable weekend warrior!

Thanks for all the input! Oh and I have a sidewinder turbo kit on it, does that make a difference in terms of gears and best tranny combo?

Thanks

Mike:)

[Edahall]

Also what kind of torque converter should I use with a good rebuild?

thanks again

Mike
Mike,
For torque converter's you might want to take a look at the 1200 rpm stall speed torque converter offered for our diesel engines.

http://www.partshp.com/Converters.htm


Description:
#2. " Super Street Raptor " Fits 700R4, 200-4R and non-LS1 4L60E transmissions (1982-1997). This stall converter is balanced, has furnace brazed fins, bearing construction and a Sonnax carbon fiber clutch. This converter can be ordered with stall speeds of 2000, 2300, 2600 or 2800 RPM. Can also be ordered with a stall speed of 1800 RPM for towing, 4WD and stock motors. We now have this converter in a 1200 RPM stall speed for diesels. Rated up to 450 horse power. No Nitrous, buy #2X if you have Nitrous. Cost $295.00

[Edahall]

Here's a very helpful rpm calculator tool.

http://www.csgnetwork.com/multirpmcalc.html


With your setup (turbo, lift and large tires), your target should be around 1800 rpm's at 60 mph for best fuel economy. With a 700R4, you would put in .70 for Transmission Final Gear Ratio.

At 60 mph with a 700R4 tranny and 36" tires I got the following:
4.11 Axles = 1611 rpm (A little slow and probably boggy)

4.56 Axles = 1788 rpm

Now if you had a Cummins under the hood of that Suburban, the 4.11 axles would work out perfectly but it would shred that 700R4 in no time. ;)

[scot5146]

Here's a very helpful rpm calculator tool.

http://www.csgnetwork.com/multirpmcalc.html


With your setup (turbo, lift and large tires), your target should be around 1800 rpm's at 60 mph for best fuel economy. With a 700R4, you would put in .70 for Transmission Final Gear Ratio.

At 60 mph with a 700R4 tranny and 36" tires I got the following:
4.11 Axles = 1611 rpm (A little slow and probably boggy)

4.56 Axles = 1788 rpm

Now if you had a Cummins under the hood of that Suburban, the 4.11 axles would work out perfectly but it would shred that 700R4 in no time. ;)
Thats funny you should say cummins because I have a 94 5.9 sitting in the shop but its for another project... I THINK!

[scot5146]

Ok y'all, again I am going with the 700r4...

BUT... can I use any 700 or is there a specific one for the 6.2 application? The problem is my old one is 2 wheel drive and i am going to converted it to 4 wheel drive. So my options are... I can use a gas 700r4 thats lying around because it will merry up to the transfer case for the 4 wheel drive...

OR

My new question is... do I use the 700r4 from the gasser or do I use a 700r4 from a 6.2 at a wrecking yard? To do my rebuild with, because I know there is a difference in the torque converter but are there other issues I should know about?

Thanks Again

Newbie

Mike:confused:

[DmaxMaverick]

There's no real difference between the trannies. Your upgrade/overhaul will even it out. Be sure to get a 1987+ "K" case (it will have a large "K" on the right/passenger side of the case....you can't miss it). The essential difference between the V8 gasser and Diesel 700's is the governor and torque converter. A good kit and uprated hard parts will negate any difference between them, once you have the correct governor and TC is installed.

[scot5146]

So I can use the gasser 700r4 I have, it has the "K" on the side of it, but then do I need to track down a governor for a 6.2?

Or can it be bought new? Do they include them in a good rebuild kit?

Thanks Again

Mike:confused:

[87max]

Defenately agree with axle swap idea, I went another route with a 400 to compete with the 700r years ago that was a set of cut gears (22%) first gear change to equal that of a 700r. No overdrive but a simple bulletproof tranny. I ran a used converter the tranny guy said was from a bus? Not sure only one i didn't break though (3 daccos ugh). I tried tci gears at first and broke 2 sets of those they ended up giving me a refund. went with A1 gears perfect
!

[DmaxMaverick]

The governor isn't included with the hardware kit. They can be bought new, best from a local tranny shop. Specify DIESEL. Not too costly, and easy to install. If you have the tranny rebuilt, specify this and the shop can easily handle it for you.

[scot5146]

Hey thanks everyone! I will post some pics and updates as the Burb process begins!

Thanks Again for all the help!

Mike:D

[Fumes]

I have a 700R4 with a GearVendor behind it, it is in a 85 GMC Van with a 6.2l and Banks Turbo. I use it to pull a 30' lightweight travel trailer. The 12 bolt rear-end has 4:10 gears. The van has over 800,000km on it with the tranny the only main thing original in the drivetrain. I had the transmission rebuilt a couple of years ago with a TransGo shift kit. Parts from a new trans were also used in it, none from a K tranny, I wish I had one. The combined weight is around 12,000 lbs and the only trouble I have is keeping the heat down in the engine (antifreeze/oil) when pulling up hill or into a good wind.

I have upgraded just recently to 2006 Duramax so my van will just be my touring vehicle.:)