t400 to t700r4 swap

[southdave]

Has anyone have any pointers before I embark on this, Iwould be grateful
have a bunch of questions: will the convertor off my 400 work on a 700r4
cross member also have to swaped?
can the drive shaft be used with modifcation?
will the win the pendant
thanks
d

 

[Westech]

really..... well the drive shafts will not work. The 700 is longer. The transfer case will have to be changed to a unit that had a 700 or 350 in front of it along with the spacer. cross member can be moved to fit where it needs to be. you will also need the linkage for the injection pump to hook up the TV cable from the trans.

 

[ConroyP]

Hi Southdave, Westech is right, the TV cable needs to be hooked to the throttle linkage. ( PITA, but once its set up, you dont need to fool with it) If you go with the stock 700R4 output shaft, I think it 28 sline, you need to make alot of changes, xfercase input, mount, driveshaft resizing etc.. But, it is easier to have a 700R4 built with a 32 spline output(same as theT400). This will allow you to reuse the origional driveshafts, mount, Xfercase input AND it has a spacer that makes it the same length as the T400. I did one last summer and it works great. If you have any questions feel free to contact me.
Pete

 

[84cucv1ton]

i was thinking it a 27 spline

 

[mangus580]

Ummm, actually the driveshafts need NOTHING. The transfer case pedastal takes care of the difference in tranny length.

I suggest you do a search, I have written up exactly what is needed about 3-4 times now (including my initial write up from mine).

 

[kennyw]

What are you putting it in, an M1009 or M1008? For an M1009 a stock transmission can be ok, but they are not known for being reliable. There are a lot of upgrade parts available that will help them last. You will also want to change out the axle gearing as 3.07 gears will not work for the OD gear. For an M1008, don't waste your money, get a 4L80E if you want OD that will hold up with the truck being used as a truck.

 

[southdave]

Thanks
I think I got
d

 

[Croatan_Kid]

Wow, lots of minconstrued information in there!

I'll make a quick run through, even though myself and Mangus580 have gone over this several times as he stated.

You'll need:

700R4
low stall, diesel torque converter
tv cable bracket
tc cable
flexplate
700R4 to NP208 tall adapter (around 11" tall)
27 spline NP208
your choice of lockup torque converter wiring
dipstick

Once you have everything gathered up and stuck in the truck, you'll see that the 700R4 combo and TH400 combo are within a 1/2" of each other. Definitely does NOT require any driveshaft changes. You will be time and money ahead to get a whole transfer case that is 27 spline rather than disassembling the 32 spline case just to swap the inputs. A new input is about 85 bucks, I got another transfer case for 100 bucks. Plus, a 32 spline output for a 700R4 is VERY pricey, last I saw it was around 400 bucks from Advance Adapters and also requires complete disassembly of the transmission. The crossmber and mounts will bolt back into the original holes.



Now, as for using a 4L80E, sure....BUT, you'll probably spend more buying a transmission and in electronics for it than you originally payed for your truck. I'd rather spend a few hundred bucks in upgraded 700R4 parts than a 4L80E anyday. With 155 HP and 240 lb/ft or TQ, a 6.2 will have a hard time tearing a built 700R4 apart. I ran my 700R4 for about 10,000 trouble free miles with 39s on the truck. The only reason I sold it was to swap in a Cummins 6BT

 

[kennyw]

Building the 700R4 can last if your not towing to full capacity of the truck (M100.

But the wiring and computer from a '91 K30 with the 6.2L and 4L80E is stand alone and doesn't cost that much if your good at searching for the right parts. I have bought those setups in the past for less than most people ask for a 700R4 by itself. It is worth looking around and pricing all of your options.

 

[southdave]

I am going home this weekend let me sort this out, I got 6.2 out of 91 van that is GM goodwrench motor installed 2004 that has 10,000 miles on it and a 700r4 that has been rebuilt for this motor trans case out of 89 chevy basically I spend way too much time in junk yard, so got pile crap to sort though

 

[Mtrdrms]

Sorry to Hijack but I can get a complete setup (700r4, tcase, shafts, linkage, brackets, etc) out of an 89 diesel civi blazer. Will this tcase/adapter work in my 1008? i know the rear driveshaft will be short but what else will I need? Thanks for the input. I just want to map out the whole job ahead of time.

Andy

 

[mangus580]

Andy, it should all bolt right in. Your drive shaft should not be short... if it is, its only by maybe 3/8"

Take lots of pics, let us know how it comes out.

 

[kennyw]

The driveshaft out of the civi blazer will be too short, but you can reuse the driveshaft from the M1008 though without modification.

Your biggest problem is going to be the durability of the stock 700R4.

 

[Mtrdrms]

Roger. Thanks for the replies guys. I will take lots of pics and document the job.

Andy

 

[Bob H]

While I understand the desire for an overdrive with a 4.56 gear ratio.
In stock form a 700R4 is a wimp, they are prone to heat failures and cost nearly triple to rebuild vs a TH400.
I had an 87 GMC1500 that I used in construction, when the 700R4 went south and the trans shop wanted $1800 to rebuild it vs $700 for a fresh TH400 installed under the truck and the fried 700R4 placed in the bed.

Sure a 700R4 can be built to be stronger than a stock TH400, but you better have deep pockets along with a trans temp gage and huge trans cooler.

I have never had a TH400 fail on me, other than twisting the insides of a Summit racing stall convertor to shrapnel.

 

[Mtrdrms]

I guess it all comes down to personal experience. I have yet to have a 700 fail on me and I'm pretty tough on my trucks with towing, hauling, off-roading and daily driving. Just like the 208 tcase. Lots of guys will warn you against them but they have always put up with my crap and got me home without a problem.

Andy

 

[mangus580]

Alot of it depends on the year of the transmission too. A 91 is one of the best years to use from what I have learned.

I am VERY happy with the 700R4 in my 1009. I just need to do something better about converter lock up... and change to my 3.73 gears

 

[CUCVHMMWV]

I love this site already!!! I hope it is ok to ask these questions here before I do a thorough search. I am just trying to figure out what I want to use on my M1008 to make the best truck I can afford. I have an '83 3/4 ton 2wd donor truck with a strong 6.2 and built 700R4 and dual tanks - and of course all the civilian goodies and a title! I also have dually hubs and HMMWV 8-bolt beadlocks and bias-ply OZ Goodyears almost ready to go. My CUCV is a non-titled, stock '84. I was thinking of swapping the motor, the 700R4, the dual tanks, and the body from the 2wd before hooking up with a Banks turbo kit.

So what would I have to do to the 700 to make it work in my application? Or is the OD overkill when running 36" tires and 4.56's? Or is even a built 700 underkill for a turbo and camper on top of 36"s? It seems like I would need to find a 4x4 tailhousing, a 27 spline 208, bolts, and gaskets... is that it? Or... would it be better to just buy the divorced NP205 with twin-stick, I just found?

 

[kennyw]

The '83 700R4 should be avoided as a starting point, you would end up needing another core anyway for all the parts your missing. Than and you want one from an '87 or later with more of the updates if you want to go that route.

36" tires and 4.56 gears would be a good combo for the 6.2L and the overdrive will make the motor happy going down the freeway... however, your going to want to build the 700R4 if you plan on towing. Also, add the biggest transmission cooler you can fit in-line with your stock cooler.

 

[CUCVHMMWV]

Thanks, I guess I'll have to contact the previous owner and see what all he did to the 700 because he told me he spent quite a bit of cash to upgrade it for towing. If an '83 were built up, it is possible that all those updates you mentioned could have been installed, correct? I asked for receipts but he never located them so I am kind of guessing right now. I will tow with the truck one day, but for now, it will be purpose built as a camper/expedition rig. Thanks for the info; it gives me a good starting point...