Transmission Parts

How to Maintain ZL20-030019 Gear Bushing? - Escaping the Kill Zone

The following recommendations will greatly lower your chances of being caught in a surprise bushing-attack during your warranty period:

• Realize that worn (or poorly made) bushings are the cause of problems from circuit leaks to component misalignment, clutch failure, broken components, friction losses, etc.

• Ensure the lubrication circuit operates normally. Vacuum test appropriate control valves and replace with oversized as necessary. Ensure lube passages are unrestricted.

• When selecting replacement bushings, choose a manufacturer with a reputation for tight tolerance specs, as shaft to bushing clearance is key to lubricant film thickness and part alignment. This is especially critical for circuits that use a Gear Bushing to seal part of a circuit. An example of bushings sealing circuits are those at the "E" clutch in ZF6HP units; most of us by now are familiar with the drivability problems and the 4F85 ratio monitoring code these units throw when the rear stator bushing wears out. Because the OE bushings utilize a less-than-optimal material in those ZF applications, this happens quite often.

• In most cases, forget bushings that are not steel-backed. The lower fatigue resistance, diminished retention properties and possibility of distortion during installation make non steel-backed bushings too risky for many applications.

• When installing bushings into aluminum housing bores, dress the leading edge of the bushing chamfer before installation. This will prevent galling of the aluminum bore.

• If you use a driver and hammer to install bushings, a change of practice is recommended. We've all done it — and gotten away with it many times — but the fact is that precision bushings can distort when driven in, causing fit and performance issues. Shock loads from driving tend to deform bushings (some more than others). Instead, always use an arbor press, which protects and preserves the integrity of the bushing ID and chamfers. Purchase or make dedicated bushing installers to use with the arbor press; replace any of these if they get dinged or scratched. Lightly lube the bushing before pressing.

• For Gear Bushings that handle high loads, use sleeve retainer or carefully stake them in after installation to prevent possible spinning.

• Prep the shaft journals and housing bores prior to installation. For best retention, the housing bore can be finished to 60–125 micro-inches RMS. For shaft journals, optimal finish is 8–12 RMS. You can do this easily by hand with the appropriate grit emery cloth; 60 grit will work just fine in the housing, and 400 grit will drop you right on the dead nuts for a shaft journal

• We're not trying to remove material here, so keep a light touch and just kiss the surface to get the best results. For the shaft, rotate the emery cloth back and forth around the axis of rotation.

• Don't forget to clean out all lube holes and passages afterward. One prepped and one non-prepped shaft. Which one would you prefer to install in your build?

• Always use manufacturer-recommended oil, which the bushing was specifically designed to be run with. The right oil must be used to maintain the desired oil thickness between bushing and shaft, and to protect the shaft as it spins.

• Dirt is the worst enemy of a Gear Bushing. Be relentless about keeping the unit clean during service.

• Ensure all chassis grounds are intact and clean, with no impermissible voltage drops. If voltage can't get to ground because of too much resistance in the designed path, it will find another way to get there — often damaging bushings in the process.

7 Signs of Zf Transmission Control Valve Failure

Plenty of transmission shifting problems can be traced back to a malfunctioning shift solenoid, including:

Delayed or unpredictable gear shifting. If you experience a delay in shifting, or your vehicle has ever jumped to another gear on its own, there is a very good chance that one or more solenoids are failing.

Skipping gears. If your vehicle has problems engaging certain gears, and it tends to skip over the "problem gear" whenever you attempt it, there's a good chance that specific solenoid is broken or worn out.

Getting stuck in certain gears. If your shift solenoid was damaged while a gear was engaged, it might cause the transmission to end up stuck in that gear.

Vehicle sluggishness. Does your vehicle seem a bit sluggish or slower than usual? In response to solenoid failures, some vehicles engage Limp Mode, a protective function for your engine that caps RPM at 2500-3000, limits shifting, and keeps you under third gear. If your vehicle has engaged this protective mode, you're probably dealing with a solenoid issue.

Inability to downshift/upshift. In many cases, solenoid problems make shifting difficult. Sometimes the transmission will be able to move upward from gear to gear without a problem, but it will be unable to shift back down. This generally occurs when the ZF transmission control valve has become stuck in an open orientation, perhaps due to physical damage to the solenoid body, wiring issues, or dirty fluid leaving foreign matter that prevents the ZF transmission control valve from shifting into position.

Check Engine light / transmission warning light. Some modern vehicles come with dashboard indicators that alert drivers to solenoid/transmission issues.

Engine continues to rev when applying the brakes. If your tachometer needle keeps climbing as you hit the brakes, there's a good chance you have a faulty solenoid.