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Unread 07-23-2010, 01:47 PM   #1
jeepstrys
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Timing Belt or Chain

Does anyone know if a 2008 JK has a timing belt or chain?

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Unread 07-23-2010, 01:53 PM   #2
RockyClymer
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The 3.8L engine uses a single block mounted 4 bearing camshaft driven by a timing chain via the cam sprocket and the crankshaft...does that help?
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Unread 07-23-2010, 04:32 PM   #3
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Does that mean it doesn't need to be replaced at 60k?
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Unread 07-23-2010, 04:38 PM   #4
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Quote:
Originally Posted by njparrothead View Post
Does that mean it doesn't need to be replaced at 60k?
Correct. An OEM timing chain only requires replacement when it gets stretched out. Typical service life of the OEM "laminated" chain runs 250-500Kmiles, with an extreme short of ~200Kmiles, and an extreme long of ~900Kmiles. You can probably double that for a "roller" chain.

A "laminated" chain has links that are built-up from plates, while a "roller" chain looks rather like a bicycle chain (there are "single rollers" - single row - and "double rollers" - two bicycle chains side-by-side. The "single roller" is far more common, and has effectively replaced the "laminated" chain.)

I flatly refuse to buy a vehicle whose engine has a belt-driven camshaft.
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Unread 07-23-2010, 04:51 PM   #5
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Quote:
Originally Posted by 5-90 View Post
Correct. An OEM timing chain only requires replacement when it gets stretched out. Typical service life of the OEM "laminated" chain runs 250-500Kmiles, with an extreme short of ~200Kmiles, and an extreme long of ~900Kmiles. You can probably double that for a "roller" chain.

A "laminated" chain has links that are built-up from plates, while a "roller" chain looks rather like a bicycle chain (there are "single rollers" - single row - and "double rollers" - two bicycle chains side-by-side. The "single roller" is far more common, and has effectively replaced the "laminated" chain.)

I flatly refuse to buy a vehicle whose engine has a belt-driven camshaft.
I used to feel that way, too.
But, having a timing belt is the only way to get 55 mpg, so I bought one.
(VW TDI, 100,000 mile belt and related components.)

Excellent info on the timing chain!
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Unread 07-23-2010, 06:56 PM   #6
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Wow!! Great info... this forum is pretty impressive... lot's of knowledge.. I have none
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Unread 07-23-2010, 07:49 PM   #7
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Originally Posted by ronjenx View Post
I used to feel that way, too.
But, having a timing belt is the only way to get 55 mpg, so I bought one.
(VW TDI, 100,000 mile belt and related components.)

Excellent info on the timing chain!
I second that. I hate the timing belt issue and had my TDI belt changed @ 100k. I guess that expense evens out over the miles with the higher MPGs obtained. Too bad most timing belts are run on interference engines b/c if the belt goes so does the whole engine head. Shouldn't have to worry too much bout the JK's chain for awhile, I'm sure there will be other issues along the way.
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Unread 07-23-2010, 09:57 PM   #8
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Originally Posted by ronjenx View Post
I used to feel that way, too.
But, having a timing belt is the only way to get 55 mpg, so I bought one.
(VW TDI, 100,000 mile belt and related components.)

Excellent info on the timing chain!
At least it's a 100K belt, and not a 50-60K.

Still, belts are for pants and accessories, not critical engine timing. Maybe I don't get 50mpg (2005 Suzuki Verona, 30-odd mpg. Still getting used to an inline six jammed in crosswise, tho...) but I've still got a timing chain.

Timing belts are such a pain - especially on front-wheel drive! They always want to run an engine mount right in the middle of the damned loop...
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Unread 07-23-2010, 10:10 PM   #9
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My timing belt broke 2k before recommended replacement(75k) and bent two valves, guess how much that cost
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Unread 07-27-2010, 02:05 PM   #10
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Thanks!

Yes, thanks for the responses. Helps a lot!
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Unread 07-27-2010, 02:38 PM   #11
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My timing belt broke 2k before recommended replacement(75k) and bent two valves, guess how much that cost
"Priceless", I hate interference motors....loved my '03 Miata and '99 Solara 4cyls which were both non-interference, no worries but, I changed the Yota at 88K when the slightest "weep/drip" was noticed at water pump....note that CA mandates 105K mile changes, often on SAME timing belt PN due to state regs of 100K mile warranty issues...so go figure the SAME car belt is 60K, 90K out of CA but, 105K IN same state, same belt too!

Have the later models cars finially all gone to 100K+ mile intervals??
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Unread 07-27-2010, 03:33 PM   #12
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"Priceless", I hate interference motors....loved my '03 Miata and '99 Solara 4cyls which were both non-interference, no worries but, I changed the Yota at 88K when the slightest "weep/drip" was noticed at water pump....note that CA mandates 105K mile changes, often on SAME timing belt PN due to state regs of 100K mile warranty issues...so go figure the SAME car belt is 60K, 90K out of CA but, 105K IN same state, same belt too!

Have the later models cars finially all gone to 100K+ mile intervals??
Yeah. The JK 3.8L is an interference motor.
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Unread 07-27-2010, 04:14 PM   #13
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Originally Posted by ronjenx View Post
Yeah. The JK 3.8L is an interference motor.
ok, correction: "interference engines with timing BELTS vice chains"...
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Unread 07-27-2010, 05:41 PM   #14
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Yeah. The JK 3.8L is an interference motor.
Never heard this term before
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Unread 07-27-2010, 06:01 PM   #15
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With Interference engines the valve will come in contact with the piston if the engine gets off timing, ie timing belt/chain breaking. So if the piston is at the upstroke and valve is open +Crash+ Bent Valves. My understanding in Non-interference engines there is enough room so the valves and pistons will not contact even if the timing goes.

I wasn't aware the 3.8 was a interference...I'm not sure what indicates an engine being one or the other? I assume efficiency and the need for higher revs
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