700R4 Swap Into M1009

White1985M1009

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Hello...First off, sorry, I know this thread is very similar to all the other 700R4 Swap threads. I would like a little more information on what needs to be done to complete the swap. Here is my situation: I have a 1989 GMC Sierra EXT Cab 4WD with a 350 that I just had the 700R4 Rebuilt about 3000 miles ago. I picked up a 1985 M1009 with 58000 on the dash. The TH400 will not stay in 3rd gear. I changed the modulator valve, checked the governor, checked the vaccum lines from the Injector pump area, and finally the kick down switch. It still will not stay in third gear. It will shift into 3rd gear above 35 mph if you let off the throttle, but as soon as I give it diesel, it shifts into 2nd. It seems when it's cool it holds 3rd longer under load, but eventually it starts acting up. From what I read on the internet, it is possibly the front pump or sticky valves. Anyways, since I have that 700R4 with a NP241, I just had a few questions. On all the other threads, no one really talked about the the drive shafts, or cross member. Will everything bolt right up with out drilling into the frame and will my stock driveshafts work? From what read, the 700R4 is 2 in longer. I'm assumeing I cannot use my NP241. So will that transfercase pedastal and input spline you mentioned in the other thread work off of the NP241? Also, all I should need is a Diesel 700R4 Torque converter, TV Cable bracket off a 6.2, Some type of Torque converter lock up switch, flex plate off my 350 and some luck. Basically everything should bolt right up correct? Thank you for all the help.
 

1984M1009

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I don't think the flexplate will work diesels have 6 lugs vs 3 for gas engines

Also the 241 in your 89 would be a drivers drop I think

The NP208 in your m1009 has a 32 spline input and the 700r4 will have 27 spline output so you either need a different t case or a 27 spline input for the TC

It can definitely be done but with 3.08 gears overdrive will probably be useless

Have you priced a rebuild for the 400 I hear they are dirt cheap to rebuild

You could probably switch to the 700r4 for 200-300 in parts if that the route you choose to go
That wouldn't include any driveshaft modifications
 
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DrJekl

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A friend of mine that rebuilds transmissions says to leave the lock up switch off as it is a problem with the 700R4.

if you do the 700R4, as stated, the 3.08 gears will be an issue. A friend put one in his but put 4.56 gears in it and is happy. The 3.08s it constantly shifted between 3 and OD.

Find yourself a 700R4 with a 208 behind it and you will have the right input shaft for the t-case and a passenger drop.

The converter will bolt up, just to three holes in the flex plate.

The 400 is cheap, again as stated above, to rebuild. It will cost less to rebuild it than it will to get the right stuff for the 700R4.
 

akonitony

New member
There are 7 different output shaft styles for the 700R4 or 4L60. There are 4 different lengths as well. The input shafts are either 27 or 30 splines, depending on if they are early or late model, and if you are putting it behind a diesel, you will need the 30 spline, or late model, as the 27 spline / early model is known to crack behind the torque of a 6.2 litre.

As for the flexplate, most of the ones I have seen are slotted to accept all six bolts, so that should not be an issue. You will need a 12V supply to your lockup solenoid, or the torque converter will generate too much heat in overdrive, and will turn your ATF to pudding over time, and kill your transmission.

I prefer to wire the valve body so it will go into lockup only in overdrive, or 4th gear. This saves the clutch in the torque converter by not having it disengage and engage with 2nd and 3rd gear, where it is really not needed. There is also a way to modify the valve body to go into lockup only in 4th gear at speeds of 55 MPH or greater via hydraulics, which nullifies the need for a 12V supply to the trannsmission.

The TH400 is truly the easiest transmission in the universe to rebuild - even easier than a TH350, believe it or not.

You will have to drill extra holes in your frame (x 4) if you change from a 3L80 (TH400) to the 4L60 (700R4). You will also need a transfer case with passenger-side drop off either another 4L60 or 3L60 (TH350), as they have the same spline count, but are totally different than any of the TH400s.

If you decide to go with the 700R4 switch, which will work nicely with 3.08:1 gears if you adjust the governor correctly (springs & weights), and you can't find a transfer case for one, PM me and I will see if I can help.

You will also want a diesel 700R4 torque converter. They no longer make the 6-pad type, and that is ok. The reason they made them with 6 pads in the first place was the diesels were ripping the pads off of them with 3 pads because of the way they were brazed onto the front. They actually changed the welding pattern and found 3 pads were enough. I recommend a GM33 torque converter for your application. It is found in the '94 - '97 PWM (Pulse-Width Modulated) vehicles. PWM was used to avoid a harsh engagement of the lockup apply, which kept down customer complaints. Since it generates a little more heat vs. a direct, single pulse engagement, they switched from a paper friction to a low-carbon semi metallic friction for the torque converter clutch. It also has the best stall speed for the 6.2 diesel at about 1400 - 1600 RPM. If you need one of these and everyone you talk to wants a whole bunch of money for one, PM me and I will see if I can help.

I like to remove the check ball in the end of the input shaft, which causes a softer apply at lockup if left in, and run the GM33 as a sort of HD modification. While it is never good to have a hard bang of a shift in any gear or with the lockup apply circuit, soft shifts or applies are where the heat increases, and also when the most wear occurs on the frictions and steels. Think of it as if you slowly let the clutch out on a standard transmission with each take-off or shift, versus shifting normally and quickly. Which way would burn out the clutch faster?

Also, if you put in a 2nd and 4th super servo, which can be done without having to take apart the inside of the transmission, you can then safely tow most moderate loads in overdrive with your 4L60. You just have to be able to take out a big snap ring that holds in the big round servo cover on the passenger side of the trans. If you have any questions and would like to talk directly to someone who has been building transmissions for about 15 years, please do not hesitate to PM me. BTW, the 700R4 is my favorite transmission to build and modify.
 
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Lawrence of Arabia

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I put a 700 in my M1028. I had to buy an adapter from, I believe, Advanced Adapters. With this adapter, I did not need to change drive shaft lengths and I was able to keep the stock tail shaft mount. The adapter included a spacer to go in between the tail of the trans & the stock tail shaft spacer/mount. Also came with correct spline to install in the 700 to mate it up to my T-Case. Truck runs way better on the HWY now.
 

White1985M1009

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Thank all of you for all the great information. I think it will be best to get the TH400 rebuilt locally in town. One of the local transmission shops quoted me around $1300 for a good rebuild. It will include a shift kit, new torque converter, and some good bands and clutches. I would like to do the 700R4 swap but it's way over my head. Once again, thank you for all the help.
 

akonitony

New member
Does that $1300 include pulling it out and installing it as well? If it doesn't it should. You might want to shop around a little for a better price. If they are doing what we call a "round trip", which is pulling it out, rebuilding it, and installing it so you don't have to touch a thing, then $1300 is not a bad price, but it is not a really good price either. You also need to ask what the warranty is on it. If it is not too late, call them back and ask if they will match prices with another shop that said they would do it for $1000 - "Round Tripped".
I would like to know which shift kit they are using. A basic Transgo shift kit, which is a very good one BTW, sells for less than $50, and does not require any special machining or extra work to install during a rebuild on a TH400, just FYI if you want to ask them what they are charging for the shift kit with you. You might want to also ask them if they modifiy the direct feed to make it a dual feed. There are other ways to make the modification, but the one I like doesn't cost a penny. It won't really be needed behind a 6.2, but if you ever put in a big block or even a small block and want to turn more than 5500 RPM, it is a good modification to have in the TH400. Also, ask them which torque converter they plan to use, I would go with the GM3-HD, and who rebuilt it. Dacco is probably the biggest rebuilder of torque converters in the USA, but they might be using Transtar, which is also good. Ask them if it has torrington bearings in place of the thrust washer that comes stock. Torrington bearings not only reduce heat and friction, but they last forever (well, that might be a little of an exaggeration).
Tell them you got big brothers on SS looking out for you, and we got your back - YO!
:grd::D:beer:;)
 
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akonitony

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One other thing: TH400s are hard on their steels, which are like the pressure plates for the friction disks to grab onto. Make sure they are not re-using the old steels, or replacing them with used steels that were reconditioned. It might last a year or two, but it won't last like one with new steels put in it, which is the way a TH400 is supposed to be rebuilt. New steels jack up the rebuild kit cost about a whopping $35, so make sure they are using them in the rebuild.
When they get done, make sure they used your HD case that came with the M1009. Those HD cases are what all the rock crawlers want, and are willing to pay top dollar for. If you crawl under your truck with a mirror and flashlight, you can shine the flashlight onto the mirror and see wherever the mirror reflects the light (pretty neat little trick I learned back when the dead sea was only sick). Look on the passanger side of the bell housing. There should be a couple of large raised letters towards the top of it that say HD in the casting. If you can't find them, then you have a regular case, and that is not a big deal, as it happens. Out of the last 6 CUCVs I've worked on, 1 had a regular case for it's TH400, and the others were HD versions.
[thumbzup]
 

Wolf.Dose

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I did not read me through all the advices in total, however I know the problem after 372000 km on a M1009. It is the modulator valve on the injection pump which I had to change 2 time for the same problem. The part is some 10 $ or so, simple low quality, lasting some 100000 km (60000 miles) or 6 to 8, if lucky 10 years to the max., most the time less! When I had to scrap my M1009 due to rust I had a valve in stock, the next failure was forseeable
THM 700: They also have a problem with higher speeds: The gears are not propperly oiled (greased) any more, so you have to drill some oil holes into the gear carries of about 6 to 8 mm diameter between the reinforcement rips.
So the change of the modulator valve is the cheepest version (2 bolts and 2 hoses).
Wolf
 

akonitony

New member
I did not read me through all the advices in total, however I know the problem after 372000 km on a M1009. It is the modulator valve on the injection pump which I had to change 2 time for the same problem. The part is some 10 $ or so, simple low quality, lasting some 100000 km (60000 miles) or 6 to 8, if lucky 10 years to the max., most the time less! When I had to scrap my M1009 due to rust I had a valve in stock, the next failure was forseeable
THM 700: They also have a problem with higher speeds: The gears are not propperly oiled (greased) any more, so you have to drill some oil holes into the gear carries of about 6 to 8 mm diameter between the reinforcement rips.
So the change of the modulator valve is the cheepest version (2 bolts and 2 hoses).
Wolf
The only modulator valve on the TH400 is on the passenger's side of the trans. I doubt this is his problem from the symptoms he's described. The Modulator valve works in concert with the governor spinning off the output shaft via worm gears and tells the trans when to up shift or downshift based on vaccuum vs. governor oil pressure. Now as for the TH700 having poor lubrication, it is true the early models had problems with the rear planetary gears lacking proper lubrication. The later models had a lube dam placed on the back. A better fix is to replace the rear output planetary with a 4L65 rear planetary gear set which has 5 pinions, and therefore increases load capacity by some 125% over the 4-pinion-type that are found in the 4L60 (700R4). Some people also replace the front gear set as well, but this is overkill IMHO, mainly because the front planetary does not bear nearly the load of the rear, and I have yet to see that gear set fail other than being wiped out from failure of other parts providing shrapnel.
 

mr.travo

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I know this is a little old, but I am having problems downshifting from 3rd into 2nd. I can be super easy on the throttle and let it shift into 3rd and then floor it and it won't downshift. Could this be the modulator? I did a tranny filter/fluid change about 1,000 miles ago and refilled with Dex/Merc.

Problem two is a slight chatter in reverse trying to back up while stopped on a hill. It only did it once that I have ever noticed but made me wonder. I have 72K miles on the clock.

Thanks!
 

Warthog

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Why post a TH400 question in a 700R4 thread?

More than likely it is the kickdown switch on the throttle pedal.
 

mr.travo

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Whoops! Man Warthog, I have been off my game the last few days. I guess I have been spending too much time reading and starting to not pay attention! Sorry for the goof-up but thanks for answering my question.

:lost: LOL!
 

Croatan_Kid

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I'm glad somebody else caught the 34 spline thing lol!


For anybody else, if you swap to a 700R4, ABSOLUTELY use a lockup switch. It will reduce heat build up and help with fuel mileage since it does away with torque converter slippage.


3.08s with a 700R4 aren't that bad, just don't use a tire any bigger than stock. There were numerous years of K10 trucks that came with 3.08s and overdrive. I don't particularly care for it, but it works.
 

mr.travo

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Is the lockup switch a toggle switch you hit at highway speeds to lock the converter? If that's the case, when you reduce speeds off the highway (exit ramps), do you have to flip it again to unlock it?

Thanks!
 

Croatan_Kid

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Well...you can do it that way, or you can use a kit that'll lock it after it hits 4th gear. If somebody sold one that waited a few seconds after hitting OD to lockup, that'd be nice, but most that I've ever see will lock the TC as soon as it goes into OD and then it wants to bog down.

I had mine on a switch back in the day when it was still powered by a 6.2.
 
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