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In the early days of the 4L60 transmission (back when they called it the 700r4), there were LOTS of week points. The technicians hated them. The backyard mechanics hated them. People were putting TH350's and 400's in place of the 700r4. It seemed that every one that was overhauled, came right back....blown up.(Not every one, but it sure seemed that way!) Actually, the TH350 was that way when it first came out; The HEI ignition system (GM electronic ignition) was that way too; people were putting Powerglides in the place of the "unreliable 350's"; They took out the HEI, and put "point-style ignition" in it's place; And lots of backyard mechanics have been known to disable the self-adjusters on drum brakes, claiming that they , too, are unreliable. Well, now, as with all the other examples, we have learned what works....and what doesn't, and are able to build a 700r4 that is reliable.

There are basically 3 major versions of the 700r4. From '82 until '84 there was a small-input-shaft unit with the same spline as the 200c transmission. It took an RPM part# C-21 (gas) or C-37 (diesel) torque converter*. Make sure not to use the later torque converter. It will install just fine, but the vehicle will not move when you are finished! From '85 to '87 there was a large input shaft version, which has the same spline as a 350 trans. It takes an RPM part # C-40 (gas) and a C-39 (diesel) torque converter*. The early torque converter ('82-'84) will not install, so there is no danger of using the early torque converter on the large shaft. From '87 1/2 up, the large shaft is still used, but GM incorporated an auxilary valve body to cushion engagement into drive.

There are some interchange problems that arise. There have been many changes to the 700r4 trans since it's first production. Obviously, input shafts (and the drums that connect to them) are different. Reverse input drums come in three different varietys ('82-early '87, which has a square oil orifice, and a steel piston, '87-'92, which has a smaller round oil orifice, and an aluminum piston, and '93, which has an aluminum piston and a larger square orifice (similar to the early drum). Pump stator supports, and their respective pump halves have changed through the years. There are, as you may have guessed, small shaft, large shaft, and '87 1/2 up auxilary valve body versions. There is an early ('82 to '84) sprag assembly that has gold thrust washers, and uses the plastic washer between it and the front planet; And the later version of the sprag assembly, that has silver thrust washers and Does not use the plastic washer between it and the front planet....put a washer there and you will eliminate all thrust end-clearance, and the unit will fry (I told you, I have to learn everything the hard way....Oh well, at least this way, I never forget this detail!). Always replace the valve body separater plate with the same code stamped on the plate. Watch the checkball location. Different years take different locations. Prior to '87 1/2, there are (5) 1/4" check balls in the case and (3) 1/4" check balls in the valve body. Later years take (4) and in rare cases (5) in the case and (2) in the valve body and (1) in the auxilary valve body.

During overhaul, I grind two flat spots on the Pressure regulater valve (GM has an updated valve which essentially does the same thing), and I replace the TV Boost valve with GM part #8634940. Replace the check ball capsule (GM# 8634400)in the case (the one that extends into the servo area). I remove it by threading a 3/8 coarse long bolt into the capsule, and "slide hammering" it out. Install using an old PR valve, and align the holes in the capsule with the opening in the servo area. I also remove the check ball that is in the capsule at the rear of the case (the one that feeds the low/reverse piston) on later units that have the ball (the early units don't have the ball). I drill four holes in the separater plate; 3/4 release hole to .078", 2nd band apply to .110", 2/3 apply to .110" and T.V. balance hole to .055". Also, make sure that the gaskets do not cover the hole in separater plate.(see photo). I install GM part # (8642970) lock-up valve on the early transmissions that don't have computer controlled lockup circuits, shortening the spring by one coil with a set of side cutters for the gas rigs, and installing the valve with the spring unaltered for the diesels. I put washers between the TV plunger and the TV valve spring to effectively make the spring longer (one washer for the gas rigs and two washers for the diesels). Put new iron vane rings (RPM #54222A) in the pump assembly (the early ones were prone to breakage). Loctite the pump seal with red #271 Loctite. Check to make sure that the rear ringgear is the updated GM version that comes as standard equipment on (I think) '85 and newer (it will have 3 lines stamped in the side of the park teeth). If not, replace with GM part # 8667055. Replace the early accumulator pistons (again I'm only guessing) '85 and older, with later pistons with rubber rings rather than teflon. On '87 and later models, I discard the 3/4 release springs and drill the 3/4 release hole in the separater plate (see photo). I install solid type teflon rings on the input shaft with a special tool (RPM # J29569). Set up the end clearance (.005-.036); The #70 selective washer seems to work 80% of the time. On the 6 cylinder versions (S10 and camaro) I replace the 3/4 apply "fingers" in the aluminum drum with the V8 version, which is lower, allowing one more clutch and steel than the original. In addition, on the 6 cylinders, I remove the aluminum plate and top overrun steel plate from the forward clutch line-up and replace with a V8 version apply pressure plate, allowing one more forward clutch and steel plate. On the same application, I replace the reverse input piston with a V8 version, which is shorter, and will accept one more clutch and steel. On the later ('87 1/2 up) reverse input drum pistons (the later drum comes with an aluminum piston.), I reduce the size of the bleed-off orifice in the piston by installing Fitzall part#77761C cup plug. On the earlier ('82-'84) 700's, I also replace the 1-2 shift valve spring with one that is a little stiffer (the gil-younger shift kit has the right spring); the early versions shifted into 2nd gear way too early. 90% of the time I replace the governor gear; they are always worn out. This transmission is equipped with a lockup torque converter; Make sure that it is working correctly on the test drive; If not, fix it.....don't ignore it, unless you like working on the same transmission, over, and over, and over and........... Check the sungear shell, carefully, for cracks around the splined area; They break occasionally. (If it seems that I am jumping around alot, I'm sorry, I am doing this all from memory as I go.)

Well that's all there is to it. I may have left something out, but I will update if I think of something else. Let me know if you have a "trick" that is not listed here. I will have the pictures up as soon as I take them (Now what the heck did I do with my Poloroid?)

* There are other part #'s, as well, but these are the most common
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