700R4 questions

[Sharecropper]

Ok I am almost ready for this 700R4 swap but have a few questions and would sincerely appreciate advice. I have acquired the taller GM 14038663 transmission-to-transfer case adapter, new GM 25515599 TV cable, and infamous TV cable bracket. I plan to purchase a completely rebuilt 700R4 from one of several sources, such as Mad Dog Transmissions http://maddogtransmissionexperts.com/home/2665592 .

I will need to specify certain parameters to whoever I purchase the transmission from and this is where I need help. Here are my questions -

1.- Are there different 700R4 cases, and should I specify a rebuilt unit utilizing a certain case?

2.- I understand the transmission will feature automatic lock-up in high (4th) gear, however what if I am slow-pulling a trailer on incline and want to keep the transmission in 3rd gear? Will the transmission lock-up in 3rd if the gear-shift selector stays in 3rd? Or should there be some other way for 3rd gear lock-up, such as a dash-mounted switch?

3.- I will be coupling my stock NP208 transfer case behind the new 700R4. If possible I want the 700R4 output tail shaft to marry to the NP208 without having to modify the NP208. What specifications should I dictate to the transmission builder to achieve this? Is the NP208 a 30-spline input? If so, can the 700R4 be fitted with a 30-spline output shaft? What about output shaft length?

4.- My truck has 13,000 original miles and was babied on a National Guard base in Arizona for 25 years. Do I also need to install a new torque converter, or will my existing converter be OK? Same question for the flex plate. Can I used my existing, or should I go ahead and install a new one while I have it torn apart? And to clarify, I have the financial ability to fund all my projects, so forget the cost - if it should be changed, I will change it.

5.- Is the factory transmission cooler adequate or should I go ahead and install a larger after-market auxiliary cooler in front of the radiator with new lines back to the transmission? Please remember I want to do this right and will fund whatever is necessary to do so.

6.- What about the speedometer gear for the 700R4? I am currently running 37" HMMWV wheels and tires and plan to continue running these for the foreseeable future. The M1028 has 4.56 gears, so is there a specific gear I should specify to get the speedometer as close as possible?

7.- What are the things I am not asking? Are there things I should be watchful for? What am I missing?

As always, I sincerely appreciate the helpful advice available on SS and want to extend my gratitude to all that reply.

 

[Recovry4x4]

I can answer a couple of questions here but not nearly all of them.
Case; you will need a K case. These are specific to 4WD trucks. They have a stronger bell to support the transfer case weight.
Transfer Case; your NP208 will have a 32 Spline input gear. The 700R4 will have a 27 Spline output shaft. I'm not aware of a 32 spline replacement but it might exist in the after market.
If your current speedo adapter is correct, it will be fine.
You will need a new flex plate and diesel converter as they are both different.
As far as lockup, there are a few different paths to take, I would speak with a rebuilder for details.
When you specify the trans, make sure they know its for a diesel as they have a different governor.
These are the answers that I have! Hope it gets you started in the right direction.

 

[corelokt]

Run the heaviest cooler you can find. Run it first, and then into the radiator. Synthetic fluid and a deep aluminum finned pan with a temp gauge. The money spent on a new converter is well spent. The T400 flex plate will not work. An NP205 T-case is good money well spent if it will see any hard use. Find the TV cable bracket ahead of time.

 

[Skinny]

If you parts start to get to expensive to mate that together, you may be better off sourcing a 700r4 with an NP241 tcase from a late 80's to 91' 6.2 diesel half ton like a burb or blazer. That way everything is there, all you need to do is rebuild the trans and install a new converter.

Do a good job of flushing that cooler in the radiator too!

 

[jpg]

I've corresponded with the folks at Monster about this. They require that you order an adapter from a third party, which they will use in their rebuild to make the 700R4 output mate properly the transfer case. I forget who the third party is, but they had a trusted provider. As I recall, it's about a $500 item. They offer a "built" 700R4 with heavier duty components, more planetary gears, etc. They recommended that HD version since it's replacing the TH400. Their HD 700R4 is supposedly in the same league as the TH400 in terms of robustness. I'm told the stock 700R4 is not.

I've not pulled the trigger on this yet, but it is in the plan. So far, all I've purchased is the TV bracket. I'll be reading your progress with interest, especially if you find a better option than Monster.

All in, it was around $2500 for a robust 700R4 rebuild configured for a CUCV, including converter, adapter, etc. For that, you get the 0.7 overdrive that knocks your 65MPH RPMs from 3140 to 2200, assuming stock tires and gearing. You can knock another 75 RPM off that by upgrading from the stock 31.7 tires to 32.8s. (Bigger tires then 33" require trimming and lifting.) That puts you at 2125 RPM at 65MPH, right at peak torque for the 6.2.

I'm sure there are cheaper options. I offer this as a data point, not a recommendation.

 

[Jozseph]

[SNIP}..........
3.- I will be coupling my stock NP208 transfer case behind the new 700R4. If possible I want the 700R4 output tail shaft to marry to the NP208 without having to modify the NP208. What specifications should I dictate to the transmission builder to achieve this? Is the NP208 a 30-spline input? If so, can the 700R4 be fitted with a 30-spline output shaft? What about output shaft length? .... {SNIP]

FWIW, one company that manufactures a GM 700R to GM NP 208 Adapter Kit is Advance Adapters, review;

http://www.advanceadapters.com/products/50-6901--gm-700r4-to-gm-np208-adapter-kit-replacing-th400/

Regards

Joseph

 

[Winston Wolf]

I just did this a swap in an m1028. The easiest route was to get a rebuilt transmission for an 80's truck. (They would be a k case). Then you can find a late 80's np208 transfer case and don't have to monkey with input/output shafts. (I paid 45$ for one and rebuilt it for 80). You can buy and rebuild a transfer case for less than the cost of modifying what you have. The tall trans to transfer adapter should be easy to find locally or on ebay. Just find a used one, it's not like they wear out. It's a whole day job with 2 experienced guys if you don't have a lift to do it correctly.

I put in a Hayden 405 cooler, and the temp gauge doesn't even get to 120 so far. I would put a 15 tooth drive gear in the transfer case, that will be correct. Fine tune the driven gear once it's driving and you can gps it, but it will be 40 something teeth. You will need a new flex plate and convertor. Flex plate would be for a 1987 6.2 truck/suburban. It doesn't need to be 6 bolt, the later ones were 3 anyways, just be sure it's a low stall for a diesel. I got one from Transtar.


As far far as lockup, it's all in the wiring you do. I have mine so it will do automatic lockup with a 4th gear psi switch and manual lockup with a toggle, or I can shut it off altogether.

I have a trans pressure gauge, as I like to see how the trans is operating.

 

[Jozseph]

Sharecropper, review "Rebuilding the GM 700-R4 by Nick Berry" http://www.berrysweb.com/700-R4-Rebuild.htm

This article was originally published in 1999 on www.TheDieselPage.com

Regards

Joseph

 

[JoshHefnerX]

I've heard both good and bad about Monster. Be sure you're getting what you're paying for.

 

[jpg]

I've heard both good and bad about Monster. Be sure you're getting what you're paying for.

Is there a better source for a 700R4? Maybe someone on SS rebuilds them?

 

[Chaski]

Ok I am almost ready for this 700R4 swap but have a few questions and would sincerely appreciate advice. I have acquired the taller GM 14038663 transmission-to-transfer case adapter, new GM 25515599 TV cable, and infamous TV cable bracket. I plan to purchase a completely rebuilt 700R4 from one of several sources, such as Mad Dog Transmissions http://maddogtransmissionexperts.com/home/2665592 .

I will need to specify certain parameters to whoever I purchase the transmission from and this is where I need help. Here are my questions -

1.- Are there different 700R4 cases, and should I specify a rebuilt unit utilizing a certain case? Yes, get a "K" case. It is easily identified by a large (like 3" tall) letter K cast into each side of the bellhousing.

2.- I understand the transmission will feature automatic lock-up in high (4th) gear, however what if I am slow-pulling a trailer on incline and want to keep the transmission in 3rd gear? Will the transmission lock-up in 3rd if the gear-shift selector stays in 3rd? Or should there be some other way for 3rd gear lock-up, such as a dash-mounted switch? I do not know, personally I have a one wire lockup that will only lockup in 4th. You could make it as complex as you wish, you might go look in some of the ATSG books on the 700r4/4l60.

3.- I will be coupling my stock NP208 transfer case behind the new 700R4. If possible I want the 700R4 output tail shaft to marry to the NP208 without having to modify the NP208. What specifications should I dictate to the transmission builder to achieve this(Take the builder your 208 and have them swap the input)? Is the NP208 a 30-spline input? (No. 27 spline) If so, can the 700R4 be fitted with a 30-spline output shaft? What about output shaft length? (I do not know of an output shafts that will do what you want. However it is really easy to swap the input gear on your 208. A 27 spline input will be in any 208 that was coupled to a 350 or 700r4. It only requires some time, cleaner, RTV and some Trans goo to hole the roller bearings in place.)

4.- My truck has 13,000 original miles and was babied on a National Guard base in Arizona for 25 years. Do I also need to install a new torque converter (YES), or will my existing converter be OK? (NO) Same question for the flex plate (I do not know the answer, but a new one is inexpensive from Jeg's or summit) Can I used my existing, or should I go ahead and install a new one while I have it torn apart? And to clarify, I have the financial ability to fund all my projects, so forget the cost - if it should be changed, I will change it.

5.- Is the factory transmission cooler adequate or should I go ahead and install a larger after-market auxiliary cooler in front of the radiator with new lines back to the transmission? Please remember I want to do this right and will fund whatever is necessary to do so. (Yes. Run an aux cooler in addition to your oem one. I had good luck with AN fittings and braded hose)

6.- What about the speedometer gear for the 700R4? (Speedo is driven off your np20 I am currently running 37" HMMWV wheels and tires and plan to continue running these for the foreseeable future. The M1028 has 4.56 gears, so is there a specific gear I should specify to get the speedometer as close as possible? (Yes, see what gears are in your 208. I believe there are two different tooth counts avaliable for the output shaft, then a bunch of different ones for the speedo drive. Also there are two different speedo drive castings, one is more eccentric then the other. Which one you use is dependent on the tooth count of your speedo drive gear. I believe you will want a 15% change. The gears are easily found on eBay.)

7.- What are the things I am not asking? Are there things I should be watchful for? What am I missing?

As always, I sincerely appreciate the helpful advice available on SS and want to extend my gratitude to all that reply.

I tried to answer most of your questions in the quote above. It is kind of a pain to read since it is hard to pick out the text I added.

You can spend a little or a lot on your 700r4 build. Personally there are a couple things that I think are must-do upgrades.
1) Use a Sonnax brand "smart shell" sunshell. It is strong, and has a really innovative way to eliminate thrust load on one of the plantary gears (thust kills them). Another popular sun shell is "the beast", the beast is strong, but it does no good for your plantary gear set. Use the Sonnax one.
2) Upgrade your servo size, I think the "corvette" one is too big, I went with the 4L70e servo. Bigger than the v8 servo, smaller than the corvette one.
3) Use a transgo brand shift kit, but only if your builder is familiar with them. If not use whatever the builder has experience with.
4) Do not use aftermarket 5 planet (4L70e) plantary gears, they are garbage. Stick with oem 4 planet geara, or spend a pile of cash and get OEM 5 planet 4L70e ones.
5) Use a rebuilt torque converter with new lockup friction material. (The monster brand one is stock friction material and a good value)
6) Consider a local transmission builder. Honestly a lot of getting a 700r4 to behave correctly is setting the TV cable correctly (a little different than norm if you use a transgo kit), tuning your governor weights and springs, and finally choosing the correct springs and orifice sizes for your application when installing the shift kit. It does involve some test drives to get it 100%

 

[Sharecropper]

I'm 99% sure I will be getting mine from Mad Dog Transmissions in Georgia. Lou will build it anyway you want it for a reasonable price.

http://maddogtransmissionexperts.com/home/2665592

 

[Chaski]

Nice. I just watched his 700r4 overview video on youtube. https://m.youtube.com/#/watch?v=idB8VA1bVLk

Looks like a good rebuilder, she seems sold on the Sonnax parts, and isn't going to up sell you to some garbage aftermarket planetary gears.

Looks like his level two or three build would be a good choice. I'd just call them up and have a good conversation with them. One thing I would ask them about is opinion on is which governor to run. My personal experience is that a stock 700r4 diesel governor is a good choice for a M1009 because of the anemic gearing. However with an M1008 and the 4.56 gears you may want a V8 governor. The governor is driven off the output shafts and gives somewhat controls shifting points. I have found that with my 4.88 gears a diesel governor was shifting way too soon. I trimmed the weights and put some different springs on it, basically making it into a V8 governor.


Here is a video showing the sonnax smart shell. http://m.youtube.com/watch?v=P_T02PDnUbI

 

[jpg]

Youtube link in the post above doesn't work for me. Link below does, at least for me. Is this the video you had in mind?

youtube.com/watch?v=idB8VA1bVLk

https://www.youtube.com/watch?v=idB8VA1bVLk

 

[Chaski]

http://www.73-87.com/7387garage/drivetrain/speedo.htm

The above link is a nice speedometer calculator.