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Before buying a used Dodge or Jeep with a 3.7 or 4.7 Engine

7:49 am Uncategorized

DennisB © Summary: Recently had a blog reader that’s interested in purchasing a used Dodge Ram Pick-up truck with a 3.7 Liter engine. He wanted my opinion on 3.7’s. Although there’s many, things to inspect and consider before purchasing any vehicle, I responded with the following things that came to mind and that I would consider before purchasing a vehicle with a 3.7 or 4.7 Mopar engine.

I personally think both the Chrysler/Jeep/Dodge 3.7 and 4.7 are good engines. The 3.7 is just like the 8 cylinder but two less cylinders (same design). Since it’s based on the 8’s design so much; there’s one problem that it has that the 8 does not. The 3.7 6cyl shakes. Something about the two less cylinders causes it to vibrate until RPM’s are raised. It almost feels like a misfire even-though nothing has to be wrong with it to feel a vibration. I only had the one 4.7 engine. It was in a 2007 Dodge Dakota and I had no problems with it, although I did trade before it had too many miles (way under 100,000 mi.). If I was going to buy one with a lot of miles, especially over a 100k, I would want to make sure the engine is not gunky inside from too few of oil changes. I’d listen to the engine from a “cold” start. Noises like lifters can be hidden sometimes if the seller warms the engine up before a potential buyer comes to test drive. I’d also notice if either one of the valve covers have been off recently. A recently removed valve cover on a 3.7 or 4.7 could mean that there’s a “rocker arm popping off” problem. They could just put it back in place without doing lifters or anything and sell the vehicle to an unsuspecting person.

Similar to Miller 8516 and 8387

We’ve sold a lot of Miller 8516-A Rocker Arm tools in the past for replacing lash adjusters (lifters) and putting the rocker arms back in. We now sell a combination Rocker Arm and Valve Spring tool that is a much better deal for doing this job. The Miller equivalent is over $300 and currently we sell the Win 3747-123 for less than a 1/3rd of that.


I’d also inspect coolant to see if that was changed often enough. I’d run the engine 20-25 minutes while looking the truck over. If there’s a leaky or outright “blown” head gasket you may see evidence coming from the tailpipe or excessive bubbles going into the coolant reservoir. I’d also find out as much as I could about maintenance and the vehicle’s history etc. It depends on how long they had it and how honest they are about revealing problems. I’ve had many buyers of used vehicles ask me after the title and money has exchanged hands “Now that it’s mine and the deal is done… do you know of anything that it needs?” Hopefully you are a good judge of character and are somewhat knowledgeable about inspecting and finding problems before you get to that point. Good Luck.

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