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Discussion Starter · #1 ·
Just swapped my 3.7 with the 3.9. Came with no info though. Was prefilled so I just topped it up since some drained out during shipping. But do I need to break it in? If so, is it the same as a new car (take it easy for 500 miles)?

P.S. - Anyone considering. Not realy a hard job. Did it by myself in 4 hours. If an idiot like me can do it I'm sure anyone with tools can 馃榾 Hardest part was getting the exhaust off.

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I just took it easy for the first 100mi or so. It's been in for over 5k mi, no prob.

I would have bet you would stick with the 3.70! I'm putting the 3.70 back in this summer before land speed trials. Not sure at this point it I'll swap back after, or just leave the 3.70 in.
 

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Whenever I have to drop the exhaust I undo it at the manifolds and unplug O2 sensors.
I rest the back on hack stands and undo and drop the front. Then just lift it off the stands and slide it out. Easier than messing with the connection from the midpipes I find.

Good to know that it can be done in 4 hours.
 

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Discussion Starter · #6 · (Edited)
Ironically getting the exhaust on was the easy part. Getting it off took me about half an hour itself. I hit the pipes with some sandpaper to smooth things and it slid right on. Put a jack under the mid mufflers with a 2x4 holding them level. That made lining it up easy and getting the middle hangers on easily.

I would have bet you would stick with the 3.70! I'm putting the 3.70 back in this summer before land speed trials. Not sure at this point it I'll swap back after, or just leave the 3.70 in.
Hoping I like it. Worst case I guess is another 4 hours to swap back and sell them. Most of my driving is around town so wanted to make 5th and 6th more usable. Also heard it makes getting started easier in traffic (not trying to launch the car). I absolutely loved it went I threw 3.73 in my mustang so hoping the same here. Will know soon enough. My old and fat ass is hurting right now so will go driving tomorrow.

Congrats on the dif swap! Didn鈥檛 know you had an m6.
Edit: reads signature and sees Barton shifter 馃ぃ
Yeah, I'm old school and just like rowing my own gears.
 

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Ironically getting the exhaust was the easy part. Getting it off took me about half an hour itself. I easily the pipes with some sandpaper to smooth things and it slid right on. Put a jack under the mid mufflers with a 2x4 holding them level. That made lining it up easy and getting the middle hangers on easily.
I have a hydraulic cart that鈥檚 foots operated and has a handle release, and you can take the handle off and lay it on the ground. Raises and lowers 36鈥. I use it for the exhaust and transmission all the time. 500lb capacity. Love Harbor Freight
 

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Discussion Starter · #8 ·
I have a hydraulic cart that鈥檚 foots operated and has a handle release, and you can take the handle off and lay it on the ground. Raises and lowers 36鈥. I use it for the exhaust and transmission all the time. 500lb capacity. Love Harbor Freight
I know the cart. Have one for moving my pinball machines 馃榾 Probably should have broke it out. Didn't even think of it. Went straight for the jack.
 
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I know the cart. Have one for moving my pinball machines 馃榾 Probably should have broke it out. Didn't even think of it. Went straight for the jack.
It鈥檚 SO MUCH easier I鈥檓 telling ya. You balance the middle of the exhaust where the mufflers are. When I take exhaust out I just drop it onto a creeper and roll it out. Going back in I use the cart. Love that thing. I come up with some pretty interesting equipment working on these cars lol
 

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Whenever I have to drop the exhaust I undo it at the manifolds and unplug O2 sensors.
I rest the back on hack stands and undo and drop the front. Then just lift it off the stands and slide it out. Easier than messing with the connection from the midpipes I find.

Good to know that it can be done in 4 hours.
Yeah I know what you mean. I feel like I have to use an exhaust pipe expander every time I want to reconnect there. Always a pain. That鈥檚 a good idea doing it at the manifolds, I鈥檒l have to try that (have to do oil pan gasket and rear main seal). I feel like I tried that before but had issues for whatever reason. Can鈥檛 remember, have had exhaust out too many times
 

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Yeah I know what you mean. I feel like I have to use an exhaust pipe expander every time I want to reconnect there. Always a pain. That鈥檚 a good idea doing it at the manifolds, I鈥檒l have to try that (have to do oil pan gasket and rear main seal). I feel like I tried that before but had issues for whatever reason. Can鈥檛 remember, have had exhaust out too many times
Like you I'm a one man operation so anything I can do to make it easier.
My car isn't a daily and hasn't seen a bunch of bad weather so everything comes apart well unlike any other car its age around here. 馃槀
 

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Discussion Starter · #14 · (Edited)
Back settled down so took the car out with my family for a late dinner. Observation so far:
  • No more gear whine. Never thought my 3.70 was noisy but I hear nothing now so I guess it was a noisy one.
  • Traffic driving is improved. Easier to get going slowly without bogging the car or slipping the clutch.
  • Car feels lighter due to the easier acceleration.
  • Feels like that I'm about a half gear different, if that makes any sense.
  • Car is comfortable in 4th at 35mph (about 1500rpm) and comfortable in 6th at 55mph. Their are several long stretches in town at 35 and 55. So this is a plus for me.
  • I feel like the car is about 200rpm higher at any gear at previous normal gears.

I took it easy so no performance acceleration feedback. Overall not a huge difference. If you are expecting a big change, probably not for you. But if you are looking for just a small change I'd recommend.
 

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Discussion Starter · #15 ·
Just a quick update to this thread now that I've put about 300 miles on the new gears. The cliff notes version is I'm loving them and wish I would have done this sooner. But, their are some buts to consider for those looking to do this as it REALLY depends on your driving style. Most of my time is around town driving so for that alone this was worth it for me. Some new observations:
  • Around town my MPG has grown about 2 mpg. Never bought the car for it's gas mileage but it's also nice to get more range out of the car.
  • With the above said, my highway cruising lost about the same 2 mpg. Highway cruise for me is generally at 75 mph of which I'm now about 250 RPM's higher than before. But if your highways are slower 55-65 mph) then you may actually see better milage with the gears. At those speeds I'm a gear higher at cruise than before and as such the car is more efficient.
  • My drone is gone for the speeds I drive. With the Mfers installed I got a pretty bad drone at 75 mph. Now the RPM's have all shifted so that is gone. It's moved more to 65 mph which works great for me as I almost never drive that speed.
  • 1st and 2nd gear are still useless from a hard launch. But I found 2nd gear starts when hollywooding a stop (slightly rolling) to be perfect. This goes along with traffic driving. I never get into 1st anymore unless I'm at a dead stop. As such, way less shifting needed when in traffic.
  • I LOVE my rolling hits in 3rd. 3rd-6th is where I really feel the higher gears when it comes to acceleration. 3rd and 4th pull much harder than before and I don't feel the need to downshift while in 5th and 6th to pass someone. I have no data to support the "pulls harder" comment but seat dyno really likes it.
  • More pops from the exhaust when engine braking.

Overall the car just feel happier in just about every way but highway cruising. If that is your norm then these probably aren't for you. I also don't think I gained any 0-60 either from these gears. 1st and 2nd are still just pedal fest on the street. On a prepped track I'm sure it's different though.

I can 100% see why Dodge didn't install these from the factory as you're shifting more frequent and their fuel rating would have suffered but this car would be perfect IMHO with these gears and a M7 (like the corvettes have). It could really use for a lower overdrive gear as turning nearly 2500 rpm at 75 mph isn't really ideal. That would be Manual Hellcat Utopia IMHO.
 

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It could really use for a lower overdrive gear as turning nearly 2500 rpm at 75 mph isn't really ideal. That would be Manual Hellcat Utopia IMHO.
^^^ This. I would even be happy with a taller ( <= 0.50 ) 6th--I'm not doing any 200 mph runs--I'd rather my 75-80mph be down in the 1100-1500 rpm range than up at 2200+. Would put mpg back on par with the A8 for freeway driving.
 

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I have not noticed the mpg improvement around town, never really checked, but the -2 on the highway is very noticeable.

With the OEM exhaust I don鈥檛 notice any drone, but I did notice more exhaust noise on the hgwy.

Theoretically the 3.70 will do 0-60 in 1st, probably one of the reasons they chose that gearing. I have not thoroughly tested as good launches are difficult enough, but I imagine the 0-60 in 1st with the 3.70 has an edge over the 3.90. But who cares.

You now need to drive an A8. It will make you appreciate the M6 much more!
 

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I have not noticed the mpg improvement around town, never really checked, but the -2 on the highway is very noticeable.

With the OEM exhaust I don鈥檛 notice any drone, but I did notice more exhaust noise on the hgwy.

Theoretically the 3.70 will do 0-60 in 1st, probably one of the reasons they chose that gearing. I have not thoroughly tested as good launches are difficult enough, but I imagine the 0-60 in 1st with the 3.70 has an edge over the 3.90. But who cares.

You now need to drive an A8. It will make you appreciate the M6 much more!
Not theoretically, it will. I used to do 1st gear 40 rolls. About half a second to shift into 2nd 馃ぃ but you win every.single.time.
 

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Discussion Starter · #19 · (Edited)
You now need to drive an A8. It will make you appreciate the M6 much more!
I actually test drove several A8's when I found out I couldn't buy a new M6 anymore. They were diffidently fun cars and I could tell they were quicker but just not my cup of tea. My wife also said I wasn't allowed to buy an auto. And as such, the search for a used M6 started.
 
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You may also want to remove the CDV if you have not already done so ;)
 
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