700r4 swap - core and rebuilt or "new"?

[cliffyp]

On another forum, someone said that TOO cool is bad, too. He's a trans rebuilder by trade. He recommended adding an external cooler inline with, and BEFORE the radiator heat exchanger. That way, you shed any excess transmission heat BEFORE dumping it into the radiator, but if it's too cool, the radiator heat exchanger can bring it back up to the correct temperature.

This was the first time I'd heard that you can get too cool with a trans. I guess it makes sense that there's an optimal temperature. We all know things don't work as well at 50 below...


What do you folks think about it?

If I recall correctly from my research for my rebuild, something around 170 is optimal and ideally you want to stay under 200. You're getting hot in the 200-220 range but acceptable for short durations. Over that and you're really starting to cook the trans.

My cooler is after the radiator and I generally run 150-160 on the highway and 170-180 in stop and go traffic. I had 2,000 lbs of concrete in the bed on a 30 minute highway drive in OD, and the needle never left 160. I was in some very soft sand, really pushing hard in 2nd gear for 15-20 minutes straight till I was off the beach. My temp got up to just under 200. Once I backed off my temp quickly fell below 180.

Running the cooler before the radiator would probably work in most situations, but I doubt you'd get get temp readings as low as 170 (I have nothing to back that up with). I would rather run 150 all day long than run 200 all day long.

 

[kmcn47]

now i'm new here and i've seen alot about the 700r4 swaps but never the real reason, is it supposed to be stronger then the th400 or is it the obvious reason of overdrive for mileage? i should have my m1009 by spring and plan on making it a nice reliable daily driver (let me know if thats impossible) so is this a good swap to do? i've got spare 700r4s around to have rebuilt, sorry if i thread jacked.

 

[wayne pick]

The 700-R4 swap will lower engine RPM and allow for higher highway speeds while retaining the trucks original gearing. There are few, if any transmissions as strong as a TH400. There are those that would argue for the Chrysler 727, I don't know about that. Your M1009 has 3.08 gearing, the 700 will constantly be shifting in and out of OD at highway speeds. This swap has become popular for the 09 as of late, I don't know why. You have a far better trans in your truck now, It's up to you.

 

[kmcn47]

so there isn't really any mileage difference by doing the 700r4? i was not aware of the kicking in and out of OD, that makes it less then desirable for me. how well do these things really handle highway miles (is 22 mpg just a myth or do they really get that at.......say 55-60) i plan for it to be my daily and i have about a 30 mile highway ride to work, mostly uphill (atleast the return trip is down)

 

[wayne pick]

The 700-R4 swap is more aimed for M1008-1010-1028-1031 trucks with 4.56 gearing. Of course lowering engine RPM at highway speeds will increase fuel milage. If you keep your foot out of the fuel tank, 22+ MPG is obtainable.

 

[5m0k3y]

Its for overdrive, after personally toasting 3 700r4 transmissions, all in half tons behind 6.2 diesels, 1 in an 83 4x4, 1 in an 82 2wd, and 1 in an 86 4x4 suburban, all highway driven (never abused offroad) i feel its money better spent although its quite a bit, to get a gearvendors overdrive and keep a th400.

I had one th400 that was in 2 different pickups, a drag car, and a daily driver malibu before i lost it in a divorce still in the malibu. The only thing i ever changed was the torque converter (for the race car), filter, fluid, and pan gasket, i may have put seals in it once too, cant remember. Always wanted to put a shift kit in it and never did.

The 2nd 700r4 i had in the 86 burb was beefed up and died in a catostrophic flex plate failure that also took out the oil pan on the 6.2.
The 700r4 in my 83 2wd 6.2 i currently cant afford to drive (thank you $4 fuel) is in the process of dieing and im quite sure its the 2nd trans in this truck already, I bought it with 87k miles and it wasnt shifting correctly, wrong governer which tells me its out of a gas burner and only a 3 bolt torque converter instead of 6.

My opinion? If you have a good th400 and the money to build a "bullettproof" 700r4, spend it (plus a bit more) on a gear vendors overdrive and keep the th400.

for 4wd > http://www.gearvendors.com/4x4gm3s.html

Al

edit- I would even take a built th350 with a lock up torque converter over the 700r4. The lock up tc is the only thing you would be missing from the th400 with od unit.

 

[wayne pick]

Good advice.

 

[MarcusOReallyus]

now i'm new here and i've seen alot about the 700r4 swaps but never the real reason, is it supposed to be stronger then the th400

The 700r4 is NOT stronger than the TH400. It is weaker.

The 700r4 is the direct ancestor of the 4L60.

The TH400 is the direct ancestor of the 4L80.



As far as I can tell, the only reason for the swap is the overdrive.

 

[Terracoma]

As far as I can tell, the only reason for the swap is the overdrive.

The lower ratio in 1st-gear is also a perk.

 

[nattieleather]

Here is my reason for going with a 700r4 instead of the TH400. 700R4 Gear ratio 1st 3.06:1 2nd 1.62:1 3rd 1:1 and 4th .70:1 were as the th400 is 1st 2.48:1, 2nd 1.48:1 3rd 1:1 4th NA. The 700R4 gives you more 1st gear and highway speed where the 6.2 isn't going to sound like it's ready to explode. I got a core off of CL for $50. which I will be using to send to rebuilder who will then build it to my specifications. I think it's a darn good swap.

 

[5m0k3y]

Here is my reason for going with a 700r4 instead of the TH400. 700R4 Gear ratio 1st 3.06:1 2nd 1.62:1 3rd 1:1 and 4th .70:1 were as the th400 is 1st 2.48:1, 2nd 1.48:1 3rd 1:1 4th NA. The 700R4 gives you more 1st gear and highway speed where the 6.2 isn't going to sound like it's ready to explode. I got a core off of CL for $50. which I will be using to send to rebuilder who will then build it to my specifications. I think it's a darn good swap.

The jump from 1st to 2nd gear is actually one of the reasons i dont care for the 700r4 in any vehicle. That and the sun shell, the 3-4 clutch pack, and the tv cable. Extra low 1st gear is ok for rock crawling. I dont see many people trying to increase 100 foot times in 6.2 diesels tho. Any one building a 700r4 should also keep in mind that gm changed something in them evey 2 years or so, which means every 2 years before about 1993 has one more problem to address than the later years. But if someone wants to build a 700r4, dont waste your time with the weaker cases and find a "K" case to rebuild. 89' I think is when they started making them, heaver 4x4's and diesels got them if i remember correctly.

 

[Recovry4x4]

The jump from 1st to 2nd gear is actually one of the reasons i dont care for the 700r4 in any vehicle. That and the sun shell, the 3-4 clutch pack, and the tv cable. Extra low 1st gear is ok for rock crawling. I dont see many people trying to increase 100 foot times in 6.2 diesels tho. Any one building a 700r4 should also keep in mind that gm changed something in them evey 2 years or so, which means every 2 years before about 1993 has one more problem to address than the later years. But if someone wants to build a 700r4, dont waste your time with the weaker cases and find a "K" case to rebuild. 89' I think is when they started making them, heaver 4x4's and diesels got them if i remember correctly.

I agree that no one is trying to improve their 100' times but the 6.2 is anemic in power. The 3.06 low just helps getting things moving easier. Spend enough seat time in the stock CUCV pickup and you will come to appreciate the gears in the 700R4.

 

[wayne pick]

The CUCV is a totally different truck with an overdrive transmission. 1st gear is a bit low for a diesel truck with 4.56 gears, but that is quickly overlooked when it hits 4th gear and then lockup, and crusing down the highway without having the engine coming through the hood.