. Known for its epicyclic design (planet and sun gears), it is commonly found on vintage marine engines like the Perkins 4.108.
Carefully separate the casting faces. Never use heavy iron pry bars or cold chisels directly against the mating seams; gouging the soft casting faces will cause persistent oil leaks even with a new gasket. Use a soft brass drift pin or a dead-blow mallet to jar the split lines loose.
Always ensure the manual matches the specific model number of your TMP gearbox, as specifications can vary between different units. 5. Tips for Working on a TMP Gearbox
Labeled diagrams showing how every part fits together, essential for reassembly. tmp gearbox workshop manual top
Standard manuals say "tap seal in until flush." The manual specifies a 3mm recess depth for the viton double-lip seal. It also mandates the use of Loctite 518 on the seal housing—a step 90% of mechanics skip, leading to premature leaks.
: The difference between "Fill" and "Full" is tiny. Overfilling can lead to leaks because the unit runs at high hydraulic pressure (roughly 80 psi ).
Avoid overfilling at all costs. High operating pressures inside the epicyclic casing will forcefully push excess oil past aging gaskets and input/output seals. 2. Essential Tools and Reassembly Parts Never use heavy iron pry bars or cold
Sometimes the manual you need is tucked away in an engine manual from a manufacturer that used TMP gearboxes. The , for instance, contains dedicated sections on the "TMP TYPE 12000 Mk II". This is a vital source for official specifications.
| Feature | Why It Matters | |---------|----------------| | | Prevents ordering mistakes during rebuilds. | | Torque specifications | Critical for bearing preload and casing bolts. | | Exploded parts view with part numbers | Essential for ordering correct bearings, synchros, and seals. | | Shift mechanism adjustment | Many TMP gearboxes have external linkage wear points. | | Common failure modes | Saves diagnostic time (e.g., 3rd gear pop-out, leaky input shaft). | | Special tool list | Some TMP units require pullers or dummy shafts. |
The TMP gearbox requires specific hydraulic fluid, typically or high-quality hydraulic oil, depending on the model's specs. typically or high-quality hydraulic oil
Once the internal planetary array is exposed, lay the components out sequentially on a clean surface. Inspect the following critical friction and pressure surfaces:
: Utilize search engines with specific keywords like the gearbox model, "workshop manual," and "top cover" or "top gearbox."
Use high-quality SAE 30 engine oil. Avoid multi-grade oils (like 10W-40 or 15W-40), as their friction modifiers can induce clutch slippage in these specific conical setups.
Because the TMP gearbox is secured to the engine bell housing by internal nuts, you must pull the gearbox and the bell housing away from the engine as a single combined unit. Because the bell housing frequently supports the rear engine mounts, ensure your engine block is safely blocked and supported from underneath prior to unbolting.