I did some searching, but didn't come up with an exact answer.

I'm getting closer and closer to swapping out my TH400 for a VERY stout 700R4 behind my 6.2 and I really need to figure out something for a TC lockup. I read out a TPS and some other stuff that were originally used in the TC circuit. I would like this to be stock or close to it and work just like stock, entirely automatic and no manual switches to engage lockup. The transmissions was oringinally from a gas motor, but I have changed converters and governors. Also, it's a 1988 model transmission.

Thanks guys!

Do a search on ebay and you can find a kit for about 15.00 that locks the converter in 4th gear only. I had one on my CJ7 and it worked great. To set up a totally stock system, requires a throttle position switch and the propper wiring in the transmission as well as the propper internal switches and a brake switch to unlock the converter when brakes are applied.

Is your truck 12v or 24 volt? The torque converter lockup (TCC) solenoid in the 700R4 is 12 volt and I don't know if a 24volt one is available. Since your truck did not have a TCC, you will need to have a switch parallel to your brake switch for a TCC cut off. The other question is, does your injector pump have the setup to install a throttle position switch on it?

To simplify the voltage problem, you might use a 24/12 volt step down transformer.

As far as installing a manual lockup, if you can get me the transmission model number, I can look up the wiring and let you know how to wire it.

Hopefully, your transmission is a "K" case which is used on 4x4 vehicles.

Not very helpful for your actual question, but I just finished the 700R4 swap in my CUCV this past week.

I just wired my TC with a toggle switch (I don't have blackout lights so I just put where the blackout light switch was so it looks stock).

The swap has to be the easiest ever, once you get the right brackets and the TV cable rod. As long as you have both the transmission and transfercases together (32 vs 27 spline tranny outputs)

The TH400/NP208 and 700R4/NP 208 are EXACTLY the same length so you can just re-use your driveshafts with no mods. I have about 300.00 in the swap (100.00 for transmission/transfercase, 100.00 torque converter, 35.00 flywheel, misc fluids etc.).

I still need to switch the speedo gear to know exactly how fast I am going, but it's nice to cruise on the highway and not have my ears bleed.

Is your truck 12v or 24 volt? The torque converter lockup (TCC) solenoid in the 700R4 is 12 volt and I don't know if a 24volt one is available.

FWIW, the only thing on a CUCV that is 24 volt is the starter. Everything else is 12V. That being said, a 12V conversion is very easy. http://www.roscommonequipmentcenter.com/news_notes/nn10.pdf

I was gunna mention the 24V thing not being a problem, but he beat me to it. Also, yes, my transmission is definitely a K case out of an '88 truck and I can't wait to get this thing in there! I've got just about 1000 bucks wrapped up in the swap with the upgraded parts I bought, transfer case, flexplate, torque converter, etc, so forth and so on.

Glad to hear your swap went well! I remember that you were having difficulties finding a TC cable bracket.



Where's the info you need for the wiring at on the transmission?

Where's the info you need for the wiring at on the transmission?

700R4/4L60 transmissions have the model no. stamped on the right, rear side just above the pan. The problem is that GM used these transmissions on many different cars during the 80s' when they were adding and updating computer controls. Seems like they all had to have slightly different wiring on their transmissions. Once you have the specific model wiring diagram, it is usually easy to adapt it to your application.

I think you will be able to have your lock up converter engage without having to use a manual switch. Your injector pump (IP) should have a vacuum switch on it which was used by the 400TH. The throttle position switch used on the 6.2 IP should fit where vacuum switch is mounted. You would then wire it as an early GM diesel (No computer control). As I mentioned earlier, you would have to add the TCC brake cut off switch. You could still add a manual switch so that you could engage the TCC in 2nd, 3rd or 4th if needed.


ajbirken

Thanks for the reference on CUCVs. I've never worked on one and GM does not give any specific info.

Manual (or automatic) lockup in 3rd gear is a very good idea. Any time you have to drive too slow to lock up in 4th gear or when you are towing or going up hills, you can shift to 3rd and lock it up. Just be careful not to overpower the clutch with a manual lockup.

Lockup in 3rd is a good idea for towing too! Keeps stuff from getting too hot.

Got some numbers for you Jmay!

The number on the side of the trans, above the pan is 8663548. Also, I see a circular set of numbers which I am going to assume to be a D.O.M. that says 11-20-89.

Also, stamped on the bellhousing on the other side down near the dipstick hole is TLF513547.


Of course, MD8 is there too, along with a big K for 4wd (yay!). A big 23 is on both sides as well, no idea what that's for.

The numbers are not right. Examples we are looking for are:

5MD137A - Mfd 1985, model MD

1YDM187A Mfd 1991, model YD

The first digit is the year, ie, 8 for l988
The 2nd & 3rd digits are letters, ie, MD, KM. MR, etc. These first two LETTERS are the model number that we need.
The 4th digit is the letter M on 4L60 models. On 700R4 models, no letter.
After the two or three letters, three numbers will be the Julian Date
The last digit is a letter, A,B,C, etc which is the shift it was built, ie day shift.

The attachment shows the location on the transmission.

Had to work to find it...it was very lightly stamped and covered with crap, but I got it.

OKCM326A

To the best of my knowledge, that is correct. If I need to go look at it again, I will, just let me know.

For what it's worth, "0KCM326A" indicates your transmission is a 1990 4L60, model number KCM which was built on the 326th day on first shift. It has a type 18 valve body wiring. I'm going to be out tomorrow, but I will try to draw up a wiring schematic for you to use. Is the transmission out where you can easily remove the pan? It might require some minor internal wiring changes because it was used on a computer controlled truck. With the pan off, you can also confirm the wiring it now has.

Yeah, I still have yet to install this trans because I've been trying to figure out the best way to make the TC lock up. It's been sitting on a table in my shop for a few weeks now....

It's strange that it comes out at a 4L60, but anything is possible. It has the same wiring as I've seen in most 700R4s though. Seems like to me that nothing can ever be simple with this build!

1988 - 1992 transmissions had a considerable number of design modifications so GM changed the designation to 4L60, but still is the basic 700R4.

A 20 year old transmission has probably been rebuilt 2 or 3 times. When a transmission shop overhauls a customers' transmission, instead of rebuilding and reinstalling the same transmission they, many times, will simply use a previously rebuilt one off the shelf which is similar to the customers requirement. That is probably why your transmission is a 1990 rather than a 1988 model.

When a transmission shop overhauls a customers' transmission, instead of rebuilding and reinstalling the same transmission they, many times, will simply use a previously rebuilt one off the shelf which is similar to the customers requirement.

Is that legal to do? I'd be paying them to rebuild my transmission, not to replace it with another one. It would be like taking the truck to a shop for an oil change and they replace the truck or the engine with one that they think is similar ...

However, how many shops have transmissions for these trucks on shelf?

Lee, Since you had your transmission upgraded with better components, I would think the shop would rebuild the one you took in. You said it came from an 88 truck, so the original transmission model number would have started with an "8", but. sometime during the trucks' life, the transmissions were switched.

I sometimes get parts from AAMCO at their rebuild shop. This is where they rebuild all of their transmissions. One mechanic just rebuilds 700R4/4L60 and similar transmissions. He is FAST and knows what he is doing. At their other shops in the Phoenix area, they just replace transmissions from shelf stock. Just like Autozone, you get a remanufactured alternator, not your own one rebuilt. This in not to say that you can't get a better rebuild from an independent transmission shop. There are good and not so good mechanics in the trade. Some will reuse parts that are marginally good and you still get charged for it in the rebuild. Even independents have shelf stock for someone who is in a hurry and needs a common transmission.

Lee, Since you had your transmission upgraded with better components, I would think the shop would rebuild the one you took in. You said it came from an 88 truck, so the original transmission model number would have started with an "8", but.


That must have been someone else? The truck was built with a TH400, some previous owner switched to a 700R4, and I had to have it rebuilt. I didn't check yet what numbers are stamped onto the transmission, but I'll check for curiosity.


At their other shops in the Phoenix area, they just replace transmissions from shelf stock.


They actually stock them? The 4wd "truck version" of a 700R4 seems to be pretty rare, particularly for a Diesel application ...


Just like Autozone, you get a remanufactured alternator, not your own one rebuilt.


That's the deal you make (or don't make): You buy a remanufactured alternator (or a new one). When you bring your truck in to have the transmission rebuild, that's the deal you make. If they do something else, like swapping it for another one, they are cheating, and if I'd find out, I would complain.

If they'd tell me in advance that they will swap it for another one, that would be a different deal. You either make that deal, or you don't. That's ok, but if they would only offer to swap, I'd probably go somewhere else because I won't know what I'd get and because the chances for them to screw things up would be much greater: It's not a stock setup, so they would have to change the wiring and maybe other things I don't know about. Nobody here knows Diesels and they might put in a tranny that is set up for a gasser ... The outcome would be rather unpredictable.

Well I have no idea if it really came from an 88 truck, that's just what I was told. Me and a buddy rebuilt it in a few days/sessions and had no problems. So far the biggest obstacle has been the lockup wiring.