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TJ 4.0L Timing Chain Replacement

By Mike Forbes

Note:  This maintenance write-up for a TJ 4.0L engine timing chain replacement is provided courtesy of Mike Forbes.  Mike was doing some work on his 2005 TJ and asked if I wanted to put the info on the site.  Since I had nothing on the site that addressed a timing chain replacement, I was happy to accept his offer.  So here it is, direct from Mike.   And Mike....thanks again for providing this info for everyone else to use.

While changing the rear main seal, I took a look at the timing chain.  It flexed just over half an inch which, according to the factory service manual, means it's up for replacement.  All in all about 4 hours.

Mopar Timing Chain
Mopar Camshaft Gear
Mopar Crankshaft Gear
Mopar front crankshaft seal
Mopar Timing Chain Cover Gasket
RTV Black

Tools Needed:
Factory Service Manual (FSM)
Inch Lbs Torque Wrench
Torque wrench that can go to 80 ft lbs
Seal Installer
Harmonic Balancer Puller
Harmonic Balancer installer
1/2" Breaker Bar
Socket extensions
Gasket Scraper
Wire Brush
10 MM socket
11 MM Socket
13 MM socket
14 MM socket
15 MM socket
16 MM Socket
19 mm socket
Large Crescent


The parts, 2 gears, a chain, a new crankshaft seal and a cover gasket.

This is easiest with the water pump out of the way.  Either replace the gasket if the pump is new or the pump if it hasn't been changed in a while.  Note: I don't think you have to remove the water pump and will attempt this on my TJ in a few weeks, I will update if different.  I picked up this LJ at 91,000 miles so I did not know the previous maintenance and chose to replace the water pump, thermostat and hoses at the same time.


Step 1:  Remove the radiator overflow container.  Simply push on the plastic nub that sticks through the shroud and lift up.  Disconnect the hose from the radiator neck.




Step 2:  Remove the fan and fan shroud.  The fan requires a big crescent wrench, quite big, looks to be 36mm.  Whack it with a 5 lb hammer is usually enough to break it free.  Once it is lose, remove the 4 11mm bolts holding the shroud to the radiator.  There are two on each side, the bottom ones are bit of a pain but are reachable from the top.

NOTE:  DO NOT STORE THE FAN FLAT. The fan MUST be stored VERTICAL.  It has to do with the thermal viscous fan drive so be careful and don't lay it on its side.

 More 4.0L Timing Chain Replacement



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