700R4 question

[wpdozer]

Hi guys, I haven't posted in a while, so here it goes, My lockup controller took a dump last night. Can I just run 12v to the lockup solinoid? I understand the trans will not lockup in 1st gear, so there is no risk of stalling it. is this correct? If I brake hard in lockup at highway speeds will i stall the engine? I really don't want to buy a new controller, it's expensive and I never really liked the way it worked.

[convert2diesel]

First of all, what vehicle are you using and what year? Second, what controller are you using?

The 700 R4 uses the solinoid ground for control. The hot side goes through the brake switch and the TPS to the solinoid and is hot when the key is on. If you have a data port (ALDA) there is a terminal that is the TCC lockup ground (bypasses the computer). I just installed a rocker switch on the dash that connected this terminal to ground. That allowed me to turn it on or off as needed.

While the TCC can't stall in 1st, the 700 is set up to stay in 2nd unless you come to a full stop. More than once I have forgotten to turn off the TCC and ended up lugging the engine as I pulled away from an intersection.

Bill

[wpdozer]

Hi Bill, sorry about the lack of info. the truck is a 1986 M1031-K30, Banks 6.2 with a 700R4 conversion, and a 1600 stall lockup converter. I used a B&M lockup controller. I just wanted to know if I could wire the lockup without using the controller. I guess you answered my question as you use a toggle switch to controll lockup. I did not know the 700 had to come to a complete stop to downshift into 1st. Guess im going to buy a new controller. I spent a lot of money rebuilding this trans and don't want to burn it up. Thanks, Wayne.

[convert2diesel]

Wayne:

If the rebuilder is local, have him check the valve body. The original 700s were totally controlled internally, with a pressure on/off switch on both the 3rd and 4th gear circuit. Later units used a switch called a pulse switch on the 3rd gear circuit to keep the computer happy. If indeed you have two switches (3rd and 4th), change them both out for on/off switches and wire the solinoid in parallel to ground through the two switches. the Solinoid has a delayed activation built in (takes about a 4 count to engage) so it does disengage between gears than locks up a moment later.

Originally, GM kept the TCC locked on deacceleration but that caused the excessive wear on the torrington bearings and overrun clutches. First fix was to place a physical off on the lower part of the TPS and another off at high throttle. An electronic TPS and a computer did the same job later on (after about 83/84???).

Even if your tranny (latest versions 87-90??? and the 4L60 non-electronic) doesn't have the two switches, the boss for the 3rd gear switch is still in the valve body and can be drilled out and tapped to accept the 3rd gear switch. The valve body has to be removed to have this done but it is possible.

The only thing I have against the aftermarket controllers is they assume you only want lockup in 4th. To get lockup in 3rd, you still have to install a switch. The above mod circumvents this.

Bill

[wpdozer]

Hea Bill, The controller I have is a B&M 70248, probably the most popular setup for 700R4 conversions. My truck is a bare bones military truck, No computer, TPS or crank sensor. It's a simple kit. Basicly, any one that can wire a tail light can install it. It uses a 40pulse/rev speed sensor to controll lockup by reading vehicle speed, not what gear it's in. I have it set at 30mph, or about half way through 2nd gear. I stated that I didn't like it becuase it's controlled electronicly, failure could cook the trans if gone un-noticed. I know all about the trans-go valvebody kit, but it only locks up in 3/4. With the turbo 6.2 and 4.56 gears Im trying to keep tempratures down as this trans was never ment for a 1-1/4 ton truck.

[convert2diesel]

Wayne;

The B&M looks like the ideal setup, if you can get it working again. Your problem may be in that your locking it up in 2nd. Not necessary and none of the OEM applications did it. The TCC gets it pressure from the 2nd gear circuit but only because they wanted a fail safe. My Caddy will lock up occasionally in 2nd but that is purely an economy thing plus it is the electronic version of your tranny.

A switch on the dash, with the hot wire routed through the brake pedal (should be a mounting hole in your bracket to install separate TCC "off" switch...a 20 dollar part from GM). Switch should be used to ground out the solinoid and the hot side should turn on with the key. This will give you full control with no computer.

Another invaluable thing is a tranny temp gauge and a big aux cooler. These are cheap and the temp sender can be mounted in the pan or my favourite place, the line pressure port on the drivers side of the tranny. Keep the tranny under 230 degrees and your good.

Hope this helps.

Bill

[wpdozer]

Hea Bill, I think the lockup controller is fooled into locking up early becuase I have the wrong speedo gear and 285/75R/16 tires. I kinda like 2nd gear lockup as in winter I snow plow some private roads and parking lots at night getting it into 2nd gear often. I have the cooling issue covered with a 16 pass Derale fan driven cooler w temp guage, and an external spin on filter. It runs at around 125deg acording to the guage, and might read a little cool as the sender is on the filter housing mount. I have the fan wired key on,fan on. Thanks for the helpfull info, I have saved it for future reference. I try to remain teachable as the years pass. Wayne.

[DmaxMaverick]

There's nothing wrong with locking in 2nd. In fact, getting the converter to lock up early and keep it locked, will help the tranny to live longer. Less time unlocked is less time building heat. Unless your gearing is too high, you won't miss the open TC. If that's the case, get more power, or live with short-lived trannies.

On my '85, when it had about 50K on it (about 87-88), I installed the best Trans-Go had at the time, and all the hard parts I could get my hands on. Sprag, rollers, bearings, shell, clutches, etc. Everything available at the time, including a cooler. Then, I bypassed all the switches, installed a toggle switch on the brake switch circuit, and a push-pull switch (on the column shifter) for apply power. With all bypasses engaged, it locks after 2nd engages, and stays there. Under power and under compression. The only time it lugs the engine is when decelerating quickly, before it has a chance to shift to 1st right before a stop. Easy enough to manage, and it never stalls completely. Simple enough to bump the switch on the column shifter to disengage it.

Anyway, it's survived over 500K miles of horrendous abuse. So much so, I've replaced the rear end more times than I care to count (never worn out, always blown out, until I upgraded to a 12 bolt and 4.10 gears). I must have done it right, because my luck just doesn't run that way.

[wpdozer]

[QUOTE=DmaxMaverick;293054]There's nothing wrong with locking in 2nd. In fact, getting the converter to lock up early and keep it locked, will help the tranny to live longer. Less time unlocked is less time building heat. Unless your gearing is too high, you won't miss the open TC. If that's the case, get more power, or live with short-lived trannies.

Hea Dmax, I don't miss the open TC at all, with 4.56 gears, the trans feels a little "tighter" in lockup if you know what I mean? And, it has a substantial braking effect going down long grades. The truck is a brutal beast as it is, and requires a lot of driver imput, no day dreaming, so an open TC is not going civilise it any. Wish I could show your post to all the 700R4 naysayers, they really can be built tough, cost me nearly $1800.00 for an out of truck rebuild. Thanks, Wayne.

[DmaxMaverick]

Yeah, not too many 700R4 advocates. I wouldn't call myself one, but I know how to make one live. Functionally, they are fantastic. The ratios are just right, even (or especially) for heavy duty. Problem is, they have some weak mechanics. If they're all addressed, they can be very stout. There are probably some significant improvements since I did mine, and I'll likely visit that before long. When I do the restore on the '85, the 700 will may be a distant memory, as the planned powerplant will likely want a LOT more. Still in the planning stage, but there's still a chance it'll go back to original, in which case the 700 will go right back in. Just not sure yet on what level of punishment I'll be prepared for.

[wpdozer]

Im not a big fan of the 700, It's what I have, so i'll make the best of it. A 4L80e is the new trend in swaps in the MV community, rebuilding and adaping it to older transfer cases to non computer trucks is expensive and time consuming. Then there is the issue of controling it with a stand alone computer, By the time you get done, you have to ask your self if the effort is worth the result. I was lucky as my truck had a simple conversion when I bought it. 700R4/27spline NP205 TC. That way, if I burn it up or break it, I can just shove another one in.LOL. If the Allison AT545 had the same 1st gear and final ratio as the 700, I would make that investment. Set it and forget it, HA!

[Robyn]

The 700R is not one of my fav gear boxes either, BUTTTTTTTTTTTT, if you want to spend some serious $$$$ on one of the little creatures you can make them live pretty well.

A 700R4 has been called by many, myself included, "A BUSY BOX" as they are almost always doing something.

I wrote a thread thats, IIRC in the chassis and drivetrain forum on all the needed stuff to make a 700R live.

The biggest issue with these boxes is the size of the internal parts.

The clutches, sprags, roller locks, shafts and such are all small.

The after market came to the rescue with replcement parts that replace the factory stuff with such things as MORE CLUTCHES, sprags with more elements and a sun shell that wont shatter into little pieces.

The one area that has always worried me a lot is the "Input drum"

The drum is aluminum and the input shaft is pressed into it.

Over time and hard use, the splines tend to loosen up around the shaft and then the drum splits

Yup, game over.

The after market has come up with a good improvement for this problem, they added a hardened steel ring to the area around the splines to support this weak spot.

The Kit consists of a new drum and a new front clutch piston (Has a larger bore to accomodate the added steel ring)

More clutches and steels in the 3-4 clutch pack really helps keep things holding well.

The 2-4 band was another area that failed often. The long reach from first to second gear places a lot of stress on the band during the shift, especially when a shift kit has been added.

The stock 700R was soooooo Mushy during the shifts that its no wonder they failed.

The aftermarket band is a great improvement.

Aside from the clutches and such, the planetaries were crap too, with some models employing powdered metal cages.
This was a bum jump as they tended to come apart under hard use.

One area that killed more 700R trannies than anything else was the "TV" System. The Throttle pressure system HAS to be right, and if its not the tranny will fry in short order.

As Maverick mentioned, the transgo shift kits are the CATSSASS to fix the programming ills of these little boxes. (Most autos for that matter)

The last 700R I built cost me nearly $1000 to build, and that was buying everything at jobber price and doing the work myself.

Once it was all done, it was an obnoxious shifting little beast, especially the 1-2 shift

This said, it lived.

Without spending some serious $$$$$$, expecting one of these boxes to live very long is only a pipe dream.

Adding a shift kit only is a good thng, and will help a lot, but without doing a complete teardown and build up using the "trick stuff" its a crap shoot.

As you mentioned the 4L80E is a good box (Not without their own issues)
but the needed controllers and such does make it a big ???????????

The TH 400 bolted to a 205 with an OD unit behind would sure begin to look good...

Other than the Dax the TH 400 can handle just about anything you can toss at it.

have fun

Missy

[convert2diesel]

There's nothing wrong with locking in 2nd. In fact, getting the converter to lock up early and keep it locked, will help the tranny to live longer. Less time unlocked is less time building heat. Unless your gearing is too high, you won't miss the open TC. If that's the case, get more power, or live with short-lived trannies.

I agree. Nothing wrong with locking it up in 2nd, except with the controller Wayne is using. It locks up the TCC and keeps it locked and has no reference other than VSS. That means all shifts above the 1-2, up and down, are done without the advantage of a fluid coupling. These trannys suffer enough with their little parts that to add the impact of essentially slam shifting them could well do some damage, especially in the infamous 2-3 shift.

I have no real problem with the 700 series transmissions, as long as they are not used at the extremes of their design perameters. The electronic versions were able, through programing, to lighten the loads at critical points to extend their lives. I have had five vehicles with these trannys in them and drove one for over 1/2 million miles without ever taking it apart. Just changed the fluid. Granted they were all in cars and mostly highway driven but never had one leave me on the side of the road.

Yes it has it's faults but in general it is a reasonable transmission. Push it beyond about 200 HP, use it in stop and go traffic, go rock crawling or Saturday night racing and your going to have a pile of broken parts on your hand. Even stuffing all the go-fast stuff in it doesn't always guarantee your going to have a bullet proof transmission if you push it beyond what the designers intended. There are lots more transmissions out there more suited. JMHO.

Bill

[Robyn]

I tend to agree with the issues of NOT locking in 2nd gear, at least not using it for high torque applications.

This process is hardest on the converter clutch, which was never designed to handle large amounts of torque.

The 700 was dreamed up to allow rigs to see some better mileage numbers and not much more.

The best way to keep a 700 alive is to lock it in 4th and above 45 MPH

Sadly the 700 is a "busy box" and by this I mean, its always doing something, locking, unlocking, shifting up/down, relocking.

Its never happy.

As long as the throttle is being moved around some, the tranny is fiddling with things.

The interal clutch o the conveter in the 700 is two (2) little bands of friction material (paper) One is about an inch wide and runs the diameter of the clutch plate, the other is about 3/4 inch wide and about 4 inches in diameter, down near the clutch plates center hub.

These two friction areas are pressed tightly against the inside of the front cover of the converter.

This is not a lot of clutch area, not at all, and will not hold a lot of torque.

The clutch was designed to hold the torque applied during "cruise power" and not pulling hills.

This said, the clutch will do it for a while, but, sooner or later it will fail.

Better than factory clutchs can used in a rebuilt, but the 700 converter is small anyway and has limited room for much more than a stock sized clutch friction area.

Better materials is more the case with these guys.

IMHO the 700 should have been limited to use in smaller passenger cars and the compact pickups.

Using these trannies in the full sized K Blazers, Burbs and 1/2 ton pickups, especially behind the 6.2 diesel was just a bomb waiting to go off.

I know, many folks have driven these countless Thousands of miles, but despite this, the 700 is just too light for any serious work.


Back when the 700R was in the throws of its tumultuous "teething" process there were numerous service bulletins issues from MA GENERAL

I was buying parts from a local tranny supplier and we were chatting about the 700, the fellow took me in his office and showed me a shelf that was about 6 feet long and there upon were stacked neatly, single sheet bulletins that filled the entire shelf.

These were stacked like a book from end to end.

That is way too many service bulletins for one gearbox.
This was about 1987 when I saw these.


I will make this recommendation, build a 700 with all the goodies, set it up with a good cooler, wire up the lockup to engage the clutch in 4th only at around 45-50 MPH and then be happy.

Transgo makes a lovely kit that will allow full lockup control without any electrical connections IIRC its called the "700LU" or ???? something like that.

I have used one of these kits. Its fully adjustable with springs and such to allow the lockup to work as you require.

A great setup for swaps and such

The 4L60E (electronic version) is somewhat better, in that the computer controls the TV system and has pretty much eliminated the related failures due to TV issues.

Just a small box thats been way overused in far to big of vehicles.

Other than the lack of an OD, the old TH 350 was a stronger box.
There was a 350C that had a lockup converter. These were short lived as far as production goes.
IIRC, the 350C was out just before the 700R

There was another unit called a 2004R These were a real piece of work

Just some thoughts


Missy

[wpdozer]

[QUOTE=Robyn;293108]

IMHO the 700 should have been limited to use in smaller passenger cars and the compact pickups.

Using these trannies in the full sized K Blazers, Burbs and 1/2 ton pickups, especially behind the 6.2 diesel was just a bomb waiting to go off.

Thats why I have a rebuilt 1989-700R4 with 75 miles on it, And a rebuilt 1982 6.2 "Red Block" with 75K miles in storage. Just waiting for the gremlin to pull the pin. Robyn, Check out the pic of my Derale cooler and external spin on filter. The vertical pipe by the rusty bracket is my straight pipe if you were wondering what it was.