Anyone running a 2WD->4WD converted 700r4 ?

[78-K5]

Question:

How many of you are running a 2WD 700R4 converted to 4WD? What is your setup (motor, tcase, lift, tires, gearing)?

Reason I'm asking:

I found a great deal on a rebuilt 700r4.. gonna cost me $200 from a good friend. Problem is it's a 2wd 700r4. Now i've searched and found that I basically need to take the tail housing off and either cut down the exisiting outputshaft or replace it with a shorter one. I'll be doing the latter (replacing it).

I've searched and basically found that no one seems to know the real difference between a 2WD and 4WD 700r4. Most seemed to say it's okay to run the 4WD. A few have said they've run it but most of the info is SPECULATION.

What I'm looking for is real-world experience... such as "I've been running it for X number of years with X setup and have had no issues (or I destroyed the tranny since it wasn't the 4WD version)." Or if you know someone else who has run this setup, any input is appreciated.

My setup and what I'll be using it for:


I'm not going to be jumping this truck. All my wheeling will be lower speed (I know I may have to re-gear the axles- different discussion). I will probably throw it into 4WD MAYBE 2-3 times a month. I live in Southern California so it's a desert. Mostly hard packed with some exposed granite and occassional sand where I'll be wheeling.

The tranny will go between my 350ci and 205 t-case. I have a 3" lift and will keep my 33" A/T tire setup for at least 2-3 more years, when I MIGHT go up to 35's. I have a 20mile round trip commute to work 4 days a week.
Hope I provided enough info to get some good replies.

Thanks!

 

[imiceman44]

The trany from a 2wd with the correct 4wd output shaft will work fine.
The K case from a 4wd truck does have a stronger case but it's marginally stronger, not enough to discard a good deal on a tranny.
It is however not that easy to change the output shaft, you will need to tear down the tranny all the way, but not as involved as rebuilding it.
I ran both kinds of cases and never broke a case.

Question:

How many of you are running a 2WD 700R4 converted to 4WD? What is your setup (motor, tcase, lift, tires, gearing)?

Reason I'm asking:

I found a great deal on a rebuilt 700r4.. gonna cost me $200 from a good friend. Problem is it's a 2wd 700r4. Now i've searched and found that I basically need to take the tail housing off and either cut down the exisiting outputshaft or replace it with a shorter one. I'll be doing the latter (replacing it).

I've searched and basically found that no one seems to know the real difference between a 2WD and 4WD 700r4. Most seemed to say it's okay to run the 4WD. A few have said they've run it but most of the info is SPECULATION.

What I'm looking for is real-world experience... such as "I've been running it for X number of years with X setup and have had no issues (or I destroyed the tranny since it wasn't the 4WD version)." Or if you know someone else who has run this setup, any input is appreciated.

My setup and what I'll be using it for:


I'm not going to be jumping this truck. All my wheeling will be lower speed (I know I may have to re-gear the axles- different discussion). I will probably throw it into 4WD MAYBE 2-3 times a month. I live in Southern California so it's a desert. Mostly hard packed with some exposed granite and occassional sand where I'll be wheeling.

The tranny will go between my 350ci and 205 t-case. I have a 3" lift and will keep my 33" A/T tire setup for at least 2-3 more years, when I MIGHT go up to 35's. I have a 20mile round trip commute to work 4 days a week.
Hope I provided enough info to get some good replies.

Thanks!

 

[78-K5]

The trany from a 2wd with the correct 4wd output shaft will work fine.
The K case from a 4wd truck does have a stronger case but it's marginally stronger, not enough to discard a good deal on a tranny.
It is however not that easy to change the output shaft, you will need to tear down the tranny all the way, but not as involved as rebuilding it.
I ran both kinds of cases and never broke a case.

Thanks for the input. What kind of wheeling were you doing on your "non-K" case? So no issues with it? I heard it's missing some supporting mounts to the engine? Or is that bull?

I'm aware of what's involved with swapping the shaft. I'm gonna pay someone to do it!

 

[imiceman44]

Thanks for the input. What kind of wheeling were you doing on your "non-K" case? So no issues with it? I heard it's missing some supporting mounts to the engine? Or is that bull?

I'm aware of what's involved with swapping the shaft. I'm gonna pay someone to do it!

The support is not in the case, it's in the torque converter cover, and the remedy to that is to drill holes in the 2wd case to accept the 6 bolt cover, and that is what was done to the case I had, I didn't do it, it was done by the PO.
I do all kinds of wheeling but I am gentle, I don't use the go pedal like some do, but rely on finesse, and controlled input.
I have done rocks to mud to sand dunes, even did some jumps but not the high speed jumps where you land nose down, it was mostly in Pismo in some of the bowls where you go down one side and fast enough to make sure you don't get stuck at the bottom so when exiting you have a little momentum that propels you out about 3 feet above ground and then when you land if you had your foot off the gas when you catch air then barely give it gas as you touch the ground, you prevent the shock loading.
I have some crazy stuff with what I had, but crazy is one thing, reckless is another, I have yet to wheel with anything bigger than a D44 front, or a 12 bolt rear, and I didn't break anything yet.

 

[4x4_76]

I have a 2wd version of 700, w/2wd output. There's a 2" spacer between the tranny and t-case. Also the tc housing is drilled to accept 4wd cast cover.

I had 6.2+700+205 combo on a K5 w/33" tires, and transmission hold up well, daily driving and occasional offroading.

 

[78-K5]

...Also the tc housing is drilled to accept 4wd cast cover....

By "tc" did you mean transmission? As in the TRANSMISSION was drilled to accept the 4wd cast cover?

Onto that, I understand the 2WD ranny has FOUR bolt holes for the cover whereas the 4WD has 6 bolt holes to hold the case cover...... Do the four bolt holes on the 2WD tranny line up with any of the holes on the 4WD cast aluminum cover?? If so, could you just run it with 4 bolts??

Thanks everyone, I'm starting to piece this together....

 

[onetonbb74]

probably torque convertor cover.

 

[4x4_76]

By "tc" did you mean transmission? As in the TRANSMISSION was drilled to accept the 4wd cast cover?

Onto that, I understand the 2WD ranny has FOUR bolt holes for the cover whereas the 4WD has 6 bolt holes to hold the case cover...... Do the four bolt holes on the 2WD tranny line up with any of the holes on the 4WD cast aluminum cover?? If so, could you just run it with 4 bolts??

TC= torque converter. And yes, I drilled holes to transmission housing. I had the cover on just by four bolts, if I remember it right the flange on a housing doesn't have enough material to be drilled for the middle holes (one on each side) of the cover.

 

[78-K5]

TC= torque converter. And yes, I drilled holes to transmission housing. I had the cover on just by four bolts, if I remember it right the flange on a housing doesn't have enough material to be drilled for the middle holes (one on each side) of the cover.

Okay, I think I understand now. So you basically had to drill the existing holes in the transmission to fit the larger hardware required for the cast aluminum dust cover..? If so, did you tap them as well or do you run longer bolts with nuts on the backside?

Doesn't sound like a big undertaking.

I'm wondering if my exisiting np203 has the same 2 support brackets and more importantly... I wonder if they're similar length. Probably not.

 

[4x4_76]

Okay, I think I understand now. So you basically had to drill the existing holes in the transmission to fit the larger hardware required for the cast aluminum dust cover..? If so, did you tap them as well or do you run longer bolts with nuts on the backside?

I just drilled straight holes and mounted the cover with longer bolts and nuts. I went to see how I had drilled the holes, and the cover was mounted with four bolts, true, but not like I said earlier. I used lowest and middle holes to secure the cover. Took me a while to figure why I didn't use the holes next to engine, but then I remembered that I drilled the holes when the tranny was in K5, and the exhaust obstructed drill to reach those holes. So you can use all six holes, there is enough material on a flange to do that.

 

[78-K5]

I just drilled straight holes and mounted the cover with longer bolts and nuts. I went to see how I had drilled the holes, and the cover was mounted with four bolts, true, but not like I said earlier. I used lowest and middle holes to secure the cover. Took me a while to figure why I didn't use the holes next to engine, but then I remembered that I drilled the holes when the tranny was in K5, and the exhaust obstructed drill to reach those holes. So you can use all six holes, there is enough material on a flange to do that.

Okay. Thanks for the explanation.

By the way, you said you HAD this setup. Did you get rid of it? Any reason in particular? Just curious.

 

[4x4_76]

By the way, you said you HAD this setup. Did you get rid of it? Any reason in particular? Just curious.

I still have all those components, engine sits in a K5, tranny and t-case on a work table. Few years ago I bought a new DD, so I started to build K5 just for off-road use, so I teared it apart. Took a while, and I started to build a Suburban using drivetrain from K5 (there's a thread on a Suburban forum) which got out of my hands, mostly due to rust. Over a year and I did nothing to neither of my projects, until just recently I started K5 again. For now I'm going with 6.2+700+203/205+D60+14FF, but if I buy a K20 Suburban, I'll replace TH-350 on it with my current 700, and when I get reasonably priced 5.3 I'll swap it to Suburban and Suburbans 350 gasser goes to K5. I got all figured out

There's a pic of K5's current state:

 

[4x4_76]

Okay. Thanks for the explanation.

Here's couple of pics:

 

[78-K5]

Hahaha... do we EVER have it all figured out???? Probably not!!

THanks for the pics... as they say, they're worth a thousand words.

 

[78-K5]

You think you could do me a HUGE favor?? Could you measure the support rods that go from the tranny cover to the motor from center of one bolt to the center of the other. I currently have an NP203 which has the support rods and am wondering if they are the same length. And if not, I'm wondering how far off they are from each other.

Whenever you get the chance, this would be a HUUUUUGE helpand would be great to compare!

Thanks!!!

Here's couple of pics:

 

[4x4_76]

You think you could do me a HUGE favor?? Could you measure the support rods that go from the tranny cover to the motor from center of one bolt to the center of the other. I currently have an NP203 which has the support rods and am wondering if they are the same length. And if not, I'm wondering how far off they are from each other.

Whenever you get the chance, this would be a HUUUUUGE helpand would be great to compare!

Thanks!!!

I would've been more than happy to help you, but unfortunately I didn't find the support rod I had on my setup. Maybe someone else could chime in?

 

[54inches]

Anyone running rocks and a Big Block with any issues?

 

[Joshatmoody]

So I bought a used 700r4 to replace the one in 92 gmc k1500. Turns out the one I bought is not a k case and has 27 teeth on the input shaft. My original case had cracked so it can’t be used. The serial number on the “newer one” indicates it’s a 1984 and the original tranny was a 1990.

Can I simply use the 84 transmission even though it’s not a k case and buy a new torque converter for it? Or swap out the input shaft from the original?

 

[diesel4me]

The early 700R4's had issues with those 27 spline pumps and they did a lot of upgrades to the 1987 and newer models,including adding a auxillary valve body and other improvements..all the hot rod and 4x4 books reccomend looking for the later versions for that reason..

If I ever replace the dying 700R4 in my '85 Burb,it'll get a 1987-90 version,that still has a throttle valve cable setup,not the electronic ones..

I have an '82 GMC K2500 that has a car or 2wd truck TH400 in it,I've beaten it pretty hard plowing since 2003,and it had no dust cover at all over the torque converter,nor were those strut rods attached,they were just hanging there--no cast dust cover to bolt them too!..I removed them--and only put a tin dust cover over the flywheel ,so far I've not had the case crack on it..

I do not go jumping the truck or do any off roading though,its just a daily driver & plow truck for my driveway..but its plowed a lot of storms 2-3 feet deep in its day..

 

[Joshatmoody]

So would you then recommend swapping all the original 1990 tranny parts into the ‘84 case assuming they are still good? That was an option too. My aim is to not spend any more money on the truck if need be. I’m on the edge to sell it as is. Hoping to just get a new torque converter and rebuild kit.