TH700R4 through 4L70E tips and tricks
by: 700guru, Alittle1, Cobalt327, Crosley, Jon
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Contents |
Summary
This section will contain some rebuild tips and tricks on the 700R4 through 4L70E transmissions.
- These transmissions use METRIC fasteners exclusively.
Rebuild manual
There are several manuals, DVD and videos found online to aid the DIY person with the rebuild process for these transmissions. ATSG manuals are suggested as a reference material for a proper rebuild. They contain specs, photos, and a few upgrades for a basic non-high performance rebuild. The related update manual is also recommended for further manufacturer upgrades and mid-year modifications, especially for 1987 models as many changes were made this year. It also contains further information and additional diagrams for identification of exact type of TCC and valve solenoid wiring for your application.
Performance section
Kits for performance modifications
TransGo seems to lead the market in quality kits. Superior Transmission brand products offer quality too.
3-4 clutch pack
The 3-4 clutch pack in these transmissions have been a problem area since production release in 1981. Clearance on the 3-4 clutch pack frictions should be in the area of 0.050" to 0.070". This can be adjusted via thin or thicker friction plates or steel plates.
3-4 clutch pack kits
- Z-Pak from Raybestos "is the patented, single-sided design clutch system that outperforms OE in torque and heat capacity without coning".
- ALTO is the original manufacturer of Red Eagle® friction materials and Kolene® steel plates and Red Eagle bands. They offer a kit with single sided red friction material friction plates. Also available are "Commercial Duty" 3-4 clutch packs that allows up to 9 friction clutches and steels for the 3-4 clutch pack. These 3-4 clutch upgrades are considered a heavy duty upgrade and will save the transmission in the event of the governor sticking in 3rd gear.
Boost valves
In a 700R4 - 4L60 non electronic trans, you will want a 0.470" to 0.500" main boost valve. For the low-reverse boost valve a 0.282" or 0.296" works well. On the low-reverse boost valve, measure the long valve land for size.
In a pre-1987 700R4 - 4L60 trans a larger low-reverse boost valve will hold off the auto upshift to 2nd gear while the shifter is in manual 1st gear.
External cooler
The key to longevity in any automatic transmission is to keep the fluid cool; therefore installing an external bypass cooler is recommended. The factory transmission coolers are an integral part of the radiator and will only cool the fluid in accordance with the engine temperature. Transmission fluid life decreases as temperatures rise above 160º F. An external transmission cooler will help to prevent ATF breakdown and torque converter "ballooning" or expansion which will cause (catastrophic) pump bushing failure. Use the largest external cooler that will fit and not block radiator airflow.
2nd gear Servo
Photo of typical 700R4 - 4L60 series servos.
- On left is Corvette size servo. Go to the OEM or various aftermarket parts sources for this servo.
- In middle is a rare servo size from SSR truck and TrailBlazer SS, not a common size to find. Numbers on inside of the bottom section will end with 159.
- On the right is common V8 sized servo, also used in 4.3 L V6 applications. Numbers on inside of the bottom section will end with 553.
Pump modifications
Drain back holes
Drain back holes from behind the converter hub seal at the bushing should be enlarged in some pumps. This is year dependent since GM enlarged this hole in the late 1980s.
The matching hole on the pump cover stator support (shown in yellow circle) should be enlarged too.
3-4 clutch oil passage
Early 700R4 - 4L60 pump covers (stator support) have an extra bleed hole in the 3-4 clutch circuit that can be plugged off.
Modification for better 3-4 clutch pack apply
On early pumps the circled hole can be tapped and plugged with a 5/16 inch set screw. GM deleted this hole in later pumps
Stake the pump bushing
Photo shows drill bit location to stake bushing. Pump bushing is removed for this operation. 1/4 inch drill bit works well here.
This photo shows the small spot made with the drill bit to stake the pump bushing in place. The spot doesn't need to be very deep.
This photo shows the pump bushing edge dimpled into the location created with a drill bit. Use a suitable rounded chisel or the side of a screw driver and hit it with a hammer to bend the bushing edge into the recess area.
Pump rotor clearance check
Photo shows the depth micrometer at 0.0015" showing clearance on the rotor. This is an ideal clearance. Set it at 0.001" to 0.002" for good pump performance.
A wide angle view photo of the depth micrometer in use.
Resources
Links
Articles that have information on transmission modification and/or rebuilding.
