How is the 3.7L balanced?

[MarksmanAkula]

I saw this brought up in another thread yesterday was am now genuinely curious.

How is the 3.7L motor balanced? Internally or externally?

Does it use weights on the harmonic balancer and torque converter to keep it concentric?
Or is it some sort of weights inside the block on the crank?

If anyone knows it would be awesome!

 

[LibertyTC]

The 3.7 engines last a long time. Trans is separate of 3.7 engine.
3.7's are known as a 90 degree odd fire v-6. The crankshaft during manufacturing would be balanced, either by shaving or adding counter weight.
https://en.wikipedia.org/wiki/V6_engine
Timing has to be set perfectly TDC & the Mopar vibration dampener is then installed, part # 53020689AB

Many folks do experience a slight shake at idle which is supposedly normal.
That being said, using the correct NGK spark plugs, as per owners manual & gapped correctly is required.
Any pcv hose leaks can cause shaking issues as well.
Coil packs fire these plugs hot & any random misfires can be seen on high end scanners like a Snap On Modis Ultra.

Auto 42Rle's were generally pretty smooth, changing the ATF + 4 /filter every 60K is a good idea.

 

[MarksmanAkula]

The 3.7 engines last a long time. Trans is separate of 3.7 engine.
3.7's are known as a 90 degree odd fire v-6. The crankshaft during manufacturing would be balanced, either by shaving or adding counter weight.
https://en.wikipedia.org/wiki/V6_engine
Timing has to be set perfectly TDC & the Mopar vibration dampener is then installed, part # 53020689AB

Many folks do experience a slight shake at idle which is supposedly normal.
That being said, using the correct NGK spark plugs, as per owners manual & gapped correctly is required.
Any pcv hose leaks can cause shaking issues as well.
Coil packs fire these plugs hot & any random misfires can be seen on high end scanners like a Snap On Modis Ultra.

Auto 42Rle's were generally pretty smooth, changing the ATF + 4 /filter every 60K is a good idea.

I'm honestly not sure what I'm asking anymore, more of trying to piece together info on what's out there.

So my jeep, a 2007, has a driveline shake at 30-45MPH, and only at certain RPM's. Sounds like highway rumble strips.

I'm trying to read up or learn about anything in the driveline that needs balanced (To see if I can eliminate that). I've heard everyone say "Change U-joints or rebalance driveshaft" and I've done that, I had the whole thing rebuilt. But the jeep still shakes. I've replaced axle bearings, new tires, balanced rims, rotated tires to see if the location changes, serviced transmission with a filter and fluid swap, balanced and had the rear shaft rebuilt, removed the front shaft to see if it was causing it, and countless other options.

At this point I'm wondering if the torque converter is going bad, in which case id just replace the trans, but I'm still gathering info on that as well. Or it could be an output bearing in either the transmission or transfer case. (But wouldn't I hear bearing noise first?)

This shake is driving me crazy, as I cant find the reason for it. So I was asking how the engines weighted to see if I may have lost or thrown a balance weight somewhere, either it be off the engine or torque converter possibly, and thats what's causing it.

I've got so many "What if's" that I dont know where to start.

 

[JeepJeepster]

The 3.7 has a useless fake cam shaft in the middle of it to balance it... When I discovered that I was completely appalled.. only thing I can figure is they designed the 4.7l first then said, 'hey, lets make it a v6 too.' Then they figured out they couldnt balance it.... So if youre going to put a fake cam shaft in it to balance it, why not just make it a good ol push rod v6? The whole point of an overhead cam is to do away with the push rods and have the rocker arms ride right on the cam.... Sigh...

Anyway, have you taken all of the disc's off to make sure there isnt some rust built up behind the rotors? Check the back side of the rotors along with the front sides also.

Do you have another vehicle you could swap wheels with? Just to make sure you dont have a bent wheel? Unfortunately you cant rule out the new tires causing it too, Ive had new tires cause a slight vibration. Heck, I just rotated the wheels on my liberty and it went away...

 

[LibertyTC]

Wow..that is not much fun, I'd say torque converter, and get transmission mounts inspected & also scanned by shop.
Does it lock up? Cruise control working? With overdrive off does it still vibrate then?

 

[MarksmanAkula]

The 3.7 has a useless fake cam shaft in the middle of it to balance it... When I discovered that I was completely appalled.. only thing I can figure is they designed the 4.7l first then said, 'hey, lets make it a v6 too.' Then they figured out they couldn't balance it.... So if you're going to put a fake cam shaft in it to balance it, why not just make it a good ol push rod v6? The whole point of an overhead cam is to do away with the push rods and have the rocker arms ride right on the cam.... Sigh...

Anyway, have you taken all of the disc's off to make sure there isn't some rust built up behind the rotors? Check the back side of the rotors along with the front sides also.

Do you have another vehicle you could swap wheels with? Just to make sure you dont have a bent wheel? Unfortunately you cant rule out the new tires causing it too, I've had new tires cause a slight vibration. Heck, I just rotated the wheels on my liberty and it went away...

Rotors are brand new as in less than 6 months, and no other wheels. Previous owner states this had been going on before we even bought it. I thought it was originally a shot U-joint due to how much play the rear shaft had when we bought it. But that wasn't the case.

And id think that the unbalanced rim would move with the location of the wheel yes? I kind of ruled that one out when I rotated the tires and the vibration did not move.

 

[MarksmanAkula]

Wow..that is not much fun, I'd say torque converter, and get transmission mounts inspected & also scanned by shop.
Does it lock up? Cruise control working? With overdrive off does it still vibrate then?

No locking up whatsoever, jeep does not have cruise control, and I've never tried the OD method.

Part of me thinks it could be transfer case related, as the case does have a significant leak at the output shaft, coming from the output bearing enclosure itself, and I've heard bad bearings can cause leaks. Then again it could be just a bad RTV seal and is leaking.

 

[JeepJeepster]

New rotors wont fix rusting unless someone cleans off the hubs.

 

[MarksmanAkula]

New rotors wont fix rusting unless someone cleans off the hubs.

Hubs? As in front wheel hubs?

Not sure what you mean.

 

[JeepJeepster]

Yep, the rotors slide onto and over the hubs and the backside of the rotor mates up with the hub. Then the wheel goes on and the rotor is sandwiched between the hub and the wheel. Gotta make sure the hub (both front and rear) is nice and clean before putting the rotor on. Since you have new rotors, you dont need to worry with also cleaning the backside of the rotor.

Just something to look at. Ive heard of this causing vibrations.

Go to the 5min mark on this video and watch. Just dont get stupid with it. If you remove too much material you'll make matters worse.

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And yes, I think a vibration would move with a wheel. When are you getting the vibration?

 

[MarksmanAkula]

Yep, the rotors slide onto and over the hubs and the backside of the rotor mates up with the hub. Then the wheel goes on and the rotor is sandwiched between the hub and the wheel. Gotta make sure the hub (both front and rear) is nice and clean before putting the rotor on. Since you have new rotors, you dont need to worry with also cleaning the backside of the rotor.

Just something to look at. Ive heard of this causing vibrations.

Go to the 5min mark on this video and watch. Just dont get stupid with it. If you remove too much material you'll make matters worse.

xc_hide_links_from_guests_guests_error_hide_media

Ohh! Now I know what you mean. Yes when I replaced the brakes I also replaced the front hubs, as well as dressed the axle hubs in the rear. Everything was smooth and clean.