4.3 700r4 swap

[trailhorse]

anybody running a 4.3 and 700r4 if so how did the swap go, I wanna increase over the road mpg and this swap should do it. I am afraid to do anything but carburated. talk to me... I am interested to know what people with this setup went through and what kind of mileage they get.

my current setup is amc 360 and tf 727 with dana 300, stiock cj7 front and rear axles. I get like 10-13 mpg and on the highway the rpm's are sick.

[LuckyCharm4x4]

I was thinking of going with the Chevy 4.3L FI Vortec motor, but I quickly decided against it and went with a Jeep 4.0L instead. It bolts right in, it has fuel injection, reliable, plenty of power, and I have got over 20mpg with 35's. I couldn't think of a better swap for a CJ.

[trailhorse]

Wait, I'm confused. You get 20 mpg's with a 4.0 with 35's or were u saying the 4.3 should give me that I'm not married to the 4.3 idea but need at least a 4 speed, what tranny are you running?

[Dudman5703]

The 4.0 and 4.3 have about the same fuel economy. Compare the 4.3 sitting in the blazer vs the 4.0 sitting in Cherokees. Same mileage/same weight.
They both have about the same hp - and the 4.0>4.3 torque wise...
which is the whole wheeling aspect.
4.3's are great and all; but IMO the 4.0s have proved themselves much more mileage wise. My dad beat the shit out of his and it ran right until the frame cracked in the YJ. Sitting right around 230k miles.
+ like Lucky said - its a direct bolt in which would save time & $.

[trailhorse]

I was thinking of going with the Chevy 4.3L FI Vortec motor, but I quickly decided against it and went with a Jeep 4.0L instead. It bolts right in, it has fuel injection, reliable, plenty of power, and I have got over 20mpg with 35's. I couldn't think of a better swap for a CJ.

What are you running for a tranny? I think the reason I was debating the 4.3 was I could squeeze in the 4 speed auto behind it. My ride is setup for auto so I was leaning towards keeping it. Although aside from purchasing the drivetrain theres another $500 for the adaptor and tranny shaft.
BUT I am easily swayed... talk to me goose...


DUDMAN - I was not really aware how similar the 2 were. I really may not have thought this through well enough. If you were me and were leaning towards keeping it automatic what would you guys do?
I was thinking with some creative placement of the 4.3 I could get away without changing the dana 300 t-case location and save from screwing around with driveshafts and all.

[Dudman5703]

Well since the PO put on the 727; hows it fit? A buddy of mine when he got his it kept rubbing when flexing; so he ordered a tin pan and we 'formed fit' the damn thing till it stopped. I was thinking maybe the th400; but you'd either have to order the amc to th400 bellhousing or find a parts one from a th400/quadratrac set up. Since I doubt you want to use a quadratrac and change your axles up.

[trailhorse]

Other than the tf 727 being pretty well cooked, I never had a problem with the fit. Until I found out otherwise I thought it was oem. But not for an 85 they stopped putting the
v8's in them in 1981 although I'm told it will fit the 258 motor as well.

still leaning towards that 4 speed auto though, unless I could find a swap for a 5 speed that would include the pedal assembly and any needed clutch mechanism or cables.

[Dudman5703]

well the bolt pattern for the AMCs are all identical. Thats why I'd really just think of keeping that instead of the pain of the 4.3; Time, $, ect.
The AW4 mates to the 4.0; 4 speed out of XJs? or maybe its ZJs IDR - I don't know much about that though. I know it does require that expensive adapter crap for the d300 though. Just trying to throw out ideas.

[LuckyCharm4x4]

I have an NV3550. It's a 2000 TJ trans. I did use my T5 that came stock in my CJ for awhile though. The bolt patterns on the back of the 4.0L and the 4.2L are the same. I prefer a manual trans hands-down in all situations. All Jeeps should be sticks. I can't help you much in the auto realm! :shrug:

[Dudman5703]

I have an NV3550. It's a 2000 TJ trans. I did use my T5 that came stock in my CJ for awhile though. The bolt patterns on the back of the 4.0L and the 4.2L are the same. I prefer a manual trans hands-down in all situations. All Jeeps should be sticks. I can't help you much in the auto realm! :shrug:

Just rub it in :/

[LuckyCharm4x4]

I will, I can't drive an auto!

[trailhorse]

---this is an opening for to many jokes to be made about spilling beer and smoking and needing the free hand for other things, but suffice to say I love an automatic tranny. I think though I may just rebuild the 727 for now and paydown my paypal debt for awhile. The kid in me wants to do everything NOWWWWW, But the adult says slow your roll and just finish the body for now. The 360 runs great so why extend myself any further. It will only cost 300 to rebuild the 727 as opposed to the cost to purchase a 4.3, 700r4 and the associated adaptors to work it all in, not to mention the exhaust and need for an electric fuel pump. I'm not giving up - just think for now it's smart money, at least this way I can market the drivetrain when she gets yanked. (boy it sucks being on a shoestring budget, but we've all been there )

[Dudman5703]

Well I do agree with the love of the 360; thats why we had added in the 4.0l will fit to it. I hear 360's are pretty awesome - though I have never been behind one :/
To add on to the auto debate - I grew up with the idea that JEEPS HAVE TO HAVE MANUAL. However, I got such a great deal on my 7, Instead of getting my I6 manual I ended up with a 304 Auto... haha....

they still wont let down that I drive an auto jeep either.

[trailhorse]

.... and in other news an upstate NY man recently filed his taxes and his wife actually is letting him keep $ 2000.00 semoilians to complete his cj7 drivetrain conversion to a chevy 350 with a 700r4 transmission.

That's right gentlemen (and chevy girl) God loves me, he looked down from his cloud and smiled on me today. I talked to a man tonight and I am going to look at his 350 4bolt main engine complete from oil pan to carb tomorrow. It came out of an 81 3/4 ton chevy truck and he says " runs perfect, no leaks, truck was rotted but engine runs great." He further says he may have a good 700r4 in the shop and I can take both of them away for a meer $ 500 smacks... Oh Happy Day !! :owow:

Yes gents, you heard right, I gave up on the 4.3 the second I compared the throaty sounds of a 350 in a cj7 on youtube today. Since my wife was so gracious I am going to assemble my drivetrain all-together outside of the vehicle and take time to measure 2 or 3 times before I install it.

SOO MUCH FOR SMART MONEY (HAH!!!)

[trailhorse]

Well I do agree with the love of the 360; thats why we had added in the 4.0l will fit to it. I hear 360's are pretty awesome - though I have never been behind one :/
To add on to the auto debate - I grew up with the idea that JEEPS HAVE TO HAVE MANUAL. However, I got such a great deal on my 7, Instead of getting my I6 manual I ended up with a 304 Auto... haha....

they still wont let down that I drive an auto jeep either.

I thought they put the autos in so you have a free hand to keep the rocks from rubbing on your rockers. LOL :rockon:

[Dudman5703]

SOO MUCH FOR SMART MONEY (HAH!!!)\
Who needs gas mileage though? Forreal.

[trailhorse]

http://i1133.photobucket.com/albums/m586/metricpatriot/IMAG0663.jpg

Here is the 350 after some cleaning up. Ran out of chevy orange paint, gotta pick up another can.
Have to clean up those pulleys and brackets yet. I have a new Holley Truck Avenger for it also.