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Toyota's full-time 4WD trucks — the Land Cruiser Prado, the V8 4Runner, the Lexus GX470 and their relatives — use a two-speed transfer case with a Torsen center differential and a drive chain that sends power to the front output. They are well built. They also cross 200,000 miles regularly, and by then the chain has stretched enough to make itself heard.
The complaint is almost always the same: a metallic rattle or slap from under the center of the truck, loudest at low speed, worse on and off the throttle, sometimes a clunk when you go from drive to reverse. Owners chase heat shields, exhaust hangers and driveshafts for months before anyone looks at the transfer case.
What A Stretched Chain Sounds Like
- Rattle or slap at 10-30 mph on light throttle, quieter at steady cruise.
- Noise changes with throttle, not engine speed. Rev it in park and it is quiet. Load and unload it while driving and it comes back.
- A single clunk on throttle tip-in or shifting between drive and reverse.
- Louder on rough pavement or over expansion joints, where the driveline is constantly loading and unloading.
- Gets worse with the center diff locked, because the chain is now carrying more of the front torque without the differential absorbing it.
Toyota full-time cases are always driving the front output. There is no 2WD mode where the chain unloads, which is why these trucks show chain wear that part-time trucks of the same mileage do not.
What Else Makes The Same Noise
| Suspect | How to tell it apart |
|---|---|
| Exhaust heat shield | Rattles with engine RPM in park. A chain does not. |
| Front or rear driveshaft U-joint / slip spline | Grab the shaft and twist against the yoke. Any play or a dry slip spline clunks on takeoff. |
| Center diff lock actuator | Lock light blinks or will not come on. Covered in our GX470 actuator guide. |
| Transfer case output bearing | A whine or growl that rises with road speed, not a rattle. |
| Transmission or engine mount | Watch the engine and transmission move under a brake-torque test. A broken mount lets the whole driveline knock. |
If it is a whine rather than a rattle, read our transfer case bearing whine guide instead.
Confirming It
- Mechanic's stethoscope on the transfer case housing at the front output while a helper loads and unloads it on a lift with the wheels off the ground. The rattle will be clearly in the case.
- Pull the drain plug and look at the magnet. Fine gray paste is normal. Heavy fuzz, or larger shiny metal flakes, points to the chain chewing on the sprockets or a bearing failing.
- Check fluid level and condition. These cases take gear oil, not ATF. If someone put ATF in it, or if it is a quart low, the chain noise gets much louder. A fluid change will not fix stretch, but the right fluid at the right level sometimes buys time.
- Measure the chain when it is apart. With the chain on the sprockets, push the slack side in. Excess deflection, or a chain that rides up on the sprocket teeth, means it is done.
The Fix
Replacing the chain means pulling the transfer case and splitting it. The chain is cheap compared to the labor, which is why you do everything else at the same time.
- New drive chain.
- Inspect both sprockets. Hooked or polished-sharp teeth will wear a new chain fast.
- Output seals and the input seal.
- Case sealant for the halves.
- Fresh gear oil, Toyota-spec 75W-90 GL-5 or the specified Toyota transfer gear oil, filled to the bottom of the fill plug.
- While the driveshafts are out, grease or replace U-joints and the slip spline.
For a shop with a lift, this is a long half-day job. In a driveway on jack stands, plan a full weekend and a transmission jack. The full-time case is heavy and awkward.
Is It Worth Fixing?
Yes, on almost any of these trucks. The body, frame and engine on a Land Cruiser or GX470 routinely outlast the chain. A used transfer case from a junkyard is the same mileage as yours, often with the same stretched chain, and you will not know until it is in. A chain, seals and fluid on a case you know is the safest money you can spend.
Leaving it is not free either. A badly stretched chain eventually jumps a tooth under load and chews the inside of the case, and then you are buying a whole transfer case.
Keep The New Chain Alive
Chain life on these cases is mostly about the oil. Toyota's maintenance schedule calls for transfer case oil changes far less often than most owners who tow, run trails or live in salt country should do them. Our rule for full-time Toyotas is every 30,000 miles, or every 15,000 if the truck tows or sees deep water. Pull the drain plug magnet every time and wipe it; the amount of paste on it tells you how the case is doing better than any noise.
Keep tire sizes matched front to rear, and replace all four tires together. A full-time case with a Torsen center differential handles small differences well, but a new front pair against a worn rear pair makes the center diff and chain work every mile. Use the center diff lock only where traction is low, never on dry pavement, and unlock it before you get back on the road.
Finally, check the vent. A plugged vent lets the case pressurize and push oil past the output seals. A case that slowly loses oil runs its new chain dry, and you are back where you started.
Parts For The Job
The 36293-35040 drive chain fits the Toyota full-time transfer cases used in the Land Cruiser Prado family. Do the chain with new fluid and output seals while the case is split.
Shop The Parts → Core Transmission Parts →FAQ
What does a bad transfer case chain sound like on a Toyota?
A metallic rattle or slap from under the center of the truck, loudest at low speed on and off the throttle, often with a clunk when shifting between drive and reverse. It follows driveline load, not engine RPM.
Do Toyota transfer cases use ATF or gear oil?
The Toyota full-time transfer cases on the Land Cruiser Prado, V8 4Runner and GX470 use gear oil, typically 75W-90 GL-5 or Toyota transfer gear oil. Confirm against the owner's manual for your year.
Will a fluid change fix transfer case chain noise?
Not if the chain is stretched. Correct fluid at the correct level can quiet it slightly and slow wear, but the only fix for a stretched chain is a new chain.
Can I drive with a stretched transfer case chain?
For a while, but it gets worse. A badly stretched chain can jump a sprocket tooth under load and damage the case, turning a chain job into a full transfer case replacement.