3.7 vs 3.9 [Archive] - Dakota Durango Message Board

Stampede4point7

03-20-2006, 08:42 PM

completely different setups... the 3.9 is part of the old magnum motor series 3.9(273), 5.2(318), 5.9(360).... the 3.9 was based off the 5.9...

"The LA 273 used the poly (A) 318 crankshaft, bearings, bearing caps, vibration damper, and conecting rods. The 273 and 318 both had a 3.31" stroke. Pistons were different, though, as the LA bore was smaller; and camshafts could not be shared due to the different valve arrangements. They did share a timing chain."

find more out about the 3.9 here... http://www.allpar.com/mopar/39.html

now for the current series 3.7, 4.7, 5.7 the 3.7 and 4.7 are identical motors aside from the 2 missing cylinders on the 3.7... and these motors are aluminum where as the older series (273, 318, 360) were cast iron I believe.

so numbers for the 3.7 and 3.9 are as follows...

size hp/tq
3.7 210/235
3.9 180/220

main point:
"Though the 3.9 ended up as a truck-only engine, it was cheap to develop and served its purpose well in 1988, though by 2001 it had been outclassed and was replaced (consistently) by a 3.7 liter version of the 4.7 liter "Next Generation" engine which had better gas mileage and more power."

skivic89

03-20-2006, 08:50 PM

Are parts interchangeable between the 3.7 and 4.7

Stampede4point7

03-20-2006, 09:06 PM

not really...because of the 2 cylinders... however a Really cheap performance upgrade for the 3.7 is to tach on a 4.7 Throttle body... you'll gain a little bit more punch in the low-mid range...

HemiDak

03-20-2006, 09:09 PM

...the 3.7 and 4.7 are identical motors aside from the 2 missing cylinders on the 3.7...

No, they're not.

Are parts interchangeable between the 3.7 and 4.7

Depends on what parts you're talking about.

suffolk_mopar

03-20-2006, 09:16 PM

No, they're not.

Depends on what parts you're talking about.

actually yes they are. my 04 3.7 is built exactly like my 03 4.7 besides the 2 missing cylinders,lol. same concept tho.

suffolk_mopar

03-20-2006, 09:17 PM

not really...because of the 2 cylinders... however a Really cheap performance upgrade for the 3.7 is to tach on a 4.7 Throttle body... you'll gain a little bit more punch in the low-mid range...

the 4.7 throttle body will not work on the 3.7. it`s shaped differently.
only option for a t/b is the fastman t/b for the 3.7. it`s worth it in my opinion.

HemiDak

03-20-2006, 09:46 PM

actually yes they are. my 04 3.7 is built exactly like my 03 4.7 besides the 2 missing cylinders,lol. same concept tho.

No, actually they're not. Compare them and prove me wrong...

http://www.allpar.com/mopar/37.html

http://www.allpar.com/mopar/47.html

addicted2blue00

03-20-2006, 09:49 PM

completely different setups... the 3.9 is part of the old magnum motor series 3.9(273), 5.2(318), 5.9(360).... the 3.9 was based off the 5.9...

the 3.9L is actually a 239 cid block, not 273, the 3.9 is a piston motor as the 3.7 is a cam motor more like the 4.7, as the 3.9 is 5.2 minus 2 pistons. the parts for 3.7 and 3.9 are not swappable, the 3.9 has more seeable power then the 3.7, only beacause it has more aftermarket parts for it, but the 3.7 has more power from the factory then the 3.9. the factory power for a 3.9 was 175hp at crank as the 3.7 had 210 or 220hp.

suffolk_mopar

03-20-2006, 10:05 PM

No, actually they're not. Compare them and prove me wrong...

http://www.allpar.com/mopar/37.html

http://www.allpar.com/mopar/47.html

too much to read for me, not that patient. altho they do apear to be based alike.
:nana:

HemiDak

03-20-2006, 10:15 PM

suffolk_mopar

03-20-2006, 10:20 PM

ya, that was alot easier. i just don`t get it. the 3.7 is really up there , not much lower than the 4.7 in hp and torque. bout time they make a v-6 seem like it`s worth a damn with todays technology. then again with todays technology we should all be getting 40 mpg.

Stampede4point7

03-21-2006, 01:09 AM

No, they're not.

Depends on what parts you're talking about.

I was just going by this page ... http://www.allpar.com/mopar/37.html

"The 3.7 liter PowerTech V-6 engine is, essentially, the 4.7 V-8 with two fewer cylinders."

Stampede4point7

03-21-2006, 01:11 AM

the 4.7 throttle body will not work on the 3.7. it`s shaped differently.
only option for a t/b is the fastman t/b for the 3.7. it`s worth it in my opinion.

Really? never knew that.. a guy I know with the 3.7 bought a 4.7 TB to put on, havn't talked to him in awhile... should probably let him know that it won't work... oops.

Stampede4point7

03-21-2006, 01:15 AM

Well, here's something a bit easier to read. This is a chart comparing the 3.7, 4.7, and 5.7 side by side.

http://www.wkjeeps.com/wk_engines.htm#SPECS

As you can see, they have a different stroke and compression ratio along with a few other things. If they were identical with 2 less cylinders, they would be the exact same like the 3.9 and 5.2 engines.

this page ... " http://www.wkjeeps.com/wk_engines.htm#SPECS " says they have the same bore and piston size and alot the same, not to be a pain, but where's the reason they aren't the same? :help:

zack

03-21-2006, 01:16 AM

anyone know what year v8 throttle body would fit on my 97 dakota v6? or should i just port and polish it.

HemiDak

03-21-2006, 02:41 AM

I was just going by this page ... http://www.allpar.com/mopar/37.html

"The 3.7 liter PowerTech V-6 engine is, essentially, the 4.7 V-8 with two fewer cylinders."

Essentially doesn't mean identical. If you read further down, you'll see this:

"Like the 4.7 on which it is based, the 3.7 features..."

this page ... " http://www.wkjeeps.com/wk_engines.htm#SPECS " says they have the same bore and piston size and alot the same, not to be a pain, but where's the reason they aren't the same? :help:

Did you read my post? :huh: They have a different stroke making the displacement for the cylinders in each motor different, very different compression ratio (obvious reasons), different firing order, and the pistions in the 4.7 weigh slightly more. That is why they are not identical...

Ben

03-21-2006, 04:22 PM

Well My buddy has had 2 Dak's with the 3.9's. Both were 2wd reg cab 5-speeds and My truck with the 3.7 auto is faster thatn both of them and gets better MPG. The 3.9 was not bad back in the day, but now the 3.7 is just about right. I do fleet managment for a living and I have had to replace alot of 3.9's this past year in the B1500 vans due to the heads warping or cracking between about 70K on up. There are alot more mod on the market for the 3.9 at this time, but look how long it was out. Give the 3.7 time and they will catch up on the mod's. The 3.7 was a Liberty engine at first, but now it is in the Dakota, Ram, Cherokee, Comander, Raider. 210hp is not bad, but i do wish that they would bump it up a tab bit. My buddys 05 Frontier has the 4.0 and it is rated at 265hp.

skivic89

03-21-2006, 05:21 PM

has any boby tried towing with the 3.7. and if so, how well did it do.

suffolk_mopar

03-21-2006, 05:45 PM

has any boby tried towing with the 3.7. and if so, how well did it do.

doesn`t do too bad. i towed a 10 ft trailer loaded with junk. and it did pretty well. just leave the o/d off and you`ll be fine.

skivic89

03-21-2006, 06:10 PM

thanks for the info. and just found something out, Jet Performance makes a stage 1 and 2 chip for the 3.7 auto, manual, 2wd and 4wd.

addicted2blue00

03-21-2006, 06:36 PM

anyone know what year v8 throttle body would fit on my 97 dakota v6? or should i just port and polish it.
try to find a in the same yr, if not 98 or 99, im thinkin you have the ball connector on the TB bracket, in 00 they changed it to a disc size connector, for other i cant say, the linkage is for the gas pedal cable, or if ya want took you factory TB to a machine shop and have it bored out to a true 48mm and new butterfly flaps put in to match the bore. with the v8 TB once installed you'd see that the intake manifold need to be bored to match the tb, which is just what i did the other week along w/ install a hughes performance belly pan.

Slow97dakota

03-21-2006, 11:50 PM

thanks for the info. and just found something out, Jet Performance makes a stage 1 and 2 chip for the 3.7 auto, manual, 2wd and 4wd.
dont waste your time/ money :biggthump

Ben

03-22-2006, 02:43 PM

dont waste your time/ money :biggthump
Yep, the Jet chips suck. Wait for the programer to come out.

skivic89

03-22-2006, 03:26 PM

thanks for the info.

skivic89

03-22-2006, 03:27 PM

doesn`t do too bad. i towed a 10 ft trailer loaded with junk. and it did pretty well. just leave the o/d off and you`ll be fine.

would buying a set of gears help with the towing at all

Ben

03-22-2006, 10:27 PM

would buying a set of gears help with the towing at all
Yeah steaper gears would help with towing, but will also cut into your MPG. What are you wanting to tow? he owners manual on my 04 3.7 auto with 3.92's gears says that it can tow up to 5,000 LBS with the proper hitch.

UsRanger11B1V

03-23-2006, 04:30 AM

Yep, the Jet chips suck. Wait for the programer to come out.

I keep on bothering the guys at Superchips. Doesn't look like its coming out anytime soon.

skivic89

03-23-2006, 02:10 PM

Yeah steaper gears would help with towing, but will also cut into your MPG. What are you wanting to tow? he owners manual on my 04 3.7 auto with 3.92's gears says that it can tow up to 5,000 LBS with the proper hitch.

I would be towing my Honda which is about 2200-24000 pounds.

Ben

03-23-2006, 02:48 PM

I would be towing my Honda which is about 2200-24000 pounds.
As long as you keep it out of OD and take it easy you should be just fine. Towin g has alot to do with how the trailer is set up, how you load it and so on. Heat is the number one killer of a Transmission so take it easy and keep it cool and it will last longer. If you have a AUTO trans and are going to be towing the Honda alot then you may wan to looking to an Extrenal trans cooler. Steaper gears make more heat in the trans on the high way at high speeds. When I went form 2.73's to 4.10's on my last Stang i did not run an External cooler like i should have and burnt up the trans on the freeway.

wahrsuul

03-23-2006, 03:00 PM

I would be towing my Honda which is about 2200-24000 pounds.

24000 lbs??!! When did Honda start making battle tanks?

skivic89

03-23-2006, 05:42 PM

24000 lbs??!! When did Honda start making battle tanks?

sorry fat figured the keyboard. that should be 2400 pounds not 24000.

wahrsuul

03-23-2006, 06:44 PM

sorry fat figured the keyboard. that should be 2400 pounds not 24000.

I figured as much, but it was an easy shot so I took it. My own typing skills leave much to be desired as well despite 25 years working on computers.

skivic89

03-23-2006, 08:04 PM

I figured as much, but it was an easy shot so I took it. My own typing skills leave much to be desired as well despite 25 years working on computers.

I know exactly how u feel. Iam a product design engineer for a division of GE aircraft. And Iam in front of the computer all day. By the end of the day my typing sucks.

sailsurf7713

04-05-2006, 11:49 PM

I know someone who tows a 3000 pound stump grinder with his 3.7 quad cab off the bumper. It does fine. I personally trust my 3.9 towing more than the 3.7, but they're both well built. Just remember to take o/d off in order to not overheat the tranny.

lllmoparlll

04-07-2006, 11:44 AM

24000 lbs??!! When did Honda start making battle tanks?

haha i found that funny...battle tanks lol :mullet:

FASTDAKOTA

05-03-2006, 05:42 AM

There about the same performance except with a bigger fuel tank. I test drove a 3.7 and a 3.9 can't feel the difference at all they feel the same. Maybe the 3.7 is a little bit Slugish. 3.9 got some kick to it little bit more torque and power.

HemiDak

05-03-2006, 07:20 PM

guehner

05-10-2006, 01:54 AM

210HP for the 3.7 and like 175HP for the 3.9

Gemmie

08-16-2006, 06:44 AM

I tow a two horse trailer loaded with two 1000lb horses, trailer weight appx. 3000lb. Have had no problems with the 3.7l and 3.92 rear end.I just take it easy and keep it out of OD

Freakdeman

09-06-2006, 08:24 PM

I just recently purchased a 05 with the 3.7 v6. Previously I had an 02 with the 3.9. Never was really satisfied with 3.9 as far as horsepower and always felt really sluggish. Never could even catch a tire. But the 3.7 seems to be a completely better engine. Side by side stock engines with no mods, to me the 3.7 is a much stronger engine.