welldonecj7

iTrader: (13)

I did some searching on there trying to find out how the MPG is with a TH350. Most of what I have found so far was with some type of overdrive trans in the vehicle. Now i know you dont do one of these swaps just based on MPG but I know that they are very efficient and can get very good MPG.

Jimbo1367

In some mag recently there was a swap with LSx EFI and a TH350 and the owner stated it stick gor 20MPG highway. Who knows what MPH and rear gear though.

welldonecj7

iTrader: (13)

Yea its tough to say, thanks for letting me know about that.

Anyone on here that has the set up in something? TH400 would give me an idea also. I know that these are not ideal trans for MPG, just trying to see what these LSx motors can do with them, my mild sbc 350 is getting between 9-10 right now and it is very mild, (but this is in a jeep so aerodynamics are not helping me.)

jhubbs

iTrader: (9)

Depends on a lot of things really. Vehicle weight, which LSx engine you're using, cam, stall, gears, how fast the vehicle is driven, how good your tune is, etc. Generally I'd say don't expect more than 15-18 MPG.

welldonecj7

iTrader: (13)

Yea, thanks for input so far guys. If I did it it would be either a lq4 lq9 or ls1. I know my set up will not get that great of MPG because what it would be in, however i would hope for better than what i get now. I know it is hard to say what it would get because so many variables, so I thought I would post this up to see the MPG some have been getting with one these trans in their rig.

jhubbs

iTrader: (9)

Well I'll be running a th350 behind a 5.3l with a tsp 224/224, 3600 stall, and 3.23 gears in a thirdgen F-body. I'm not expecting more than 15 or 16 MPG. Mine is carbureted though, so that doesn't help MPG's much. Neither does my heavy right foot for that matter

Transamthunder

I had thought also of using a turbo 350 for my third gen TA, I een have the B&M adaptor for 10 years now and a driveshaft for a metrec tranny still sitting in my garage that I trip over from time to time. I dont have tranny anymore though since it needed rebuilt, but my 700r4 that I do have which did work but accidently got left in the rain now needs gone through since water doesnt do well with clutches. But with all the new kits out it is better to rebuild the overdrive into a stronger unit. It doesnt pertain to ls1 engines, but on another forum there is a guy running a tpi third gen TA with mostly stock motor and 2 Buick turbos getting about 18mpg through his turbo 400, his gears are like 3.08 or 2.73. He ended up running mid nines with it too. Just a jy setup, and his own tuning with a holly cammander setup. I would think mid teens if you dont romp on it much on the highway. You going fuelie or carb on that jeep?

nismoknights

my car gets shitting mpg because im always on it..

but if its straight freeway its gotta be close to 18ish or so..

welldonecj7

iTrader: (13)

thanks for the info so far guys, anyone else that has any experiance with this please also post up what you have got.



If i do it it will be fuel injected, I have not decided to do it yet however. When i first started my jeep project i wanted to do it with an LS1 and 4l60e, however at that point they wanted like $5,000 plus for a pullout and I was going to high school working part time so did not have funding for it. Not to mention all the swap stuff was not availible yet and less companies doing the wiring harness stuff. But now that the prices have came down on some of the motors I am still wanting to do this and have been thinking about maybe doing it. The engine in it now a a crate 330 deluxe with an edelbrock carb. It has shorty headers with 2.5" exhaust and we have tried to tune the carb to get it as efficient as possible, however i manage to get about 9 or if really lucky 10mpg, (doesnt really seem to matter much if highway or city maybe changes .5mpg). The engine in it runs great so it is hard for me to decide if i want to start something like this, however i really like the lsx style motor and know there is so much potential with it. I will be keeping it a fairly streetable gear with a 3.73 and 33" tire.

lsxmalibu

iTrader: (50)

i get 20 with a th350 and 3.73's, cruising at 55-60

welldonecj7

iTrader: (13)

Assuming that this is with the set up in your sig? How much does your car weigh? I dont think that I would get that but it would be awesome if i could, even close to that would be nice.

bozzhawg

20 MPG with a 3 speed and 3.73 gear?
I don't know about that bro, are you talking about highway driving.....?
I have never seen a car that revs around 3000+ at 60mph get 20 mpg

I will tell you this it depends on the weight of the car, rear gear, and converter stall........

If you have anytype of performance gear above 3.42+ .... now you tipping towards less efficiency in terms of MPG...... If you use anytype of performnce stall 2500+ forget MPG...... I don't care how efficient it is the higher the stall kiss mpg goodbye....

Your hardest decision or compromise will be determining if you want street or strip......... To gain one thing you have to compromise another...... And with a 3 speed tranny, the only way to see any kind og MPG efficiency is to run a 2.73, 2.90,3.08,3.32,3.31,3.42 type gears ...... 3.73,4.11,4.30.4.56 for get it.......

frito1

iTrader: (12)

no lockup converter and no overdrive.... don't expect much. I will somewhat disagree with the above posted... I had a 2000 trans am that I built the ls1 in with a 4000 stall. With the lockup 4000 stall converter, I still got 23+ mpg on the highway and ran 11.20's at the track. Then turned the A/C on and drove home... not a bad deal

bozzhawg

I was really talking about the converter, rear, and 3 speed with no overdrive.... 3000+ rpms at 60 will not yeild 20 mpg ......

welldonecj7

iTrader: (13)

I wish i could have done the swap i origninally wanted to do with ls style engine and 4l60e trans. At this point i have it all set up though with the sbc th350, to change i would have to get a new adapter for the transfercase too and they are not cheap and i have a new relbuilt th350 in it, it is set up nice how it is, i just really like the ls style engine so much potiential effiecent and reliable.