Hey everyone,

I've got a 2.8 V6 MPFi with the T5 manual transmission and a 3.42 rear end at the moment and it's running at around 2kRPM at 60mph and by using the 2.73 I can get down to 1.4kRPM at 60 mph for gas mileage (UK = extortionate prices).

My question is aside from the obvious difference in acceleration, are there any other things I should know/be made aware of, good or bad, I'm listening; before I commit to the sale of the 2.73. It's not a posi and its on drums before anyone asks!

Thanks in advance!

 

If you are only looking at it from a fuel economy aspect, probably the way to go. Gotta think though, will it be worth it when you can barely get out of your own way?
What kind of fuel economy are you currently getting? There may be other ways to improve mileage without changing out rear gears. I used to get mid 20s average with a modded 3.4L running rich and 3.42 LSD. I didn't baby it either.

 

At the moment I'm seeing 21 which aint great and I'm trying to work out why its so low. I need to run it properly without lots of standing around on idle to see what it's really doing i think. But i have a chance on the 2.73 for not a lot of money and i do want to use this a lot more than i am now. My daily does 60mpg so I'm really feeling the difference in fuel. To put it into perspective my other toy, the 2.8 TD Daihatsu 4x4 does more to the gallon that the firebird at the moment!

 

21 probably isn't bad for how old the car/technology is on it. You'll never see 30s mpg or anything like that if that's what you're hoping for. Have you done a full tune up on the car? What kind of prices are they getting for unleaded gas over there, out of curiosity?
What are you driving for a daily to get 60mpg? One other question, are you converting from metric to english to get your numbers? 60 seems very high for even some hybrids around.

 

Gas is around $8.15 a gallon here. Really expensive.

I’ve read some guys get high 20’s with these MPFi’s with the T5?

Yeah the car is a full but and bolt restoration and I mean every nut and bolt, and component!

My daily is an Opel Vectra 1.9 CDTi and it’s been mapped. Google it!

No, although out gas is in litres our MPG is the same, although I think your gallons are different somehow. I remember when I owned a RAM the truck said it was getting 11 and when I looked into it that was actually like 9 in U.K. gallons!

 

The difference may be one of "Imperial Gallons" VS "US Gallons" .

I wouldn't go for the 2:73 because at the lower RPMs for the same MPH wouldn't you be having to step further into the gas pedal to get it to maintain the same speed at the lower RPM ?

And yea , I've traveled in Europe and seen the prices you folks pay for gas , there would be literal riots at the pumps if it ever went that high here ...

 

It'd be absolutely miserable to drive, and your gas mileage will most likely go down because you'll have to push the engine harder to make up for the lack of gearing.

I ran a 2.73 geared 8.8 in my 2.3L Mustang for awhile, both with the 4spd manual and 1bbl carbed engine, and later with the 2.3 turbocharged EFI setup, and T5. I got killer highway mileage with the carbed setup, but everything else sucked. After the EFI turbo swap the car was a real pain to drive around town because the gearing put the engine so far out of the power band that it was hard to find a gear where the car could keep pace with traffic without having to constantly be shifting up or down. Driveability went up exponentially when I turned the 2.73 ring and pinion into a paperweight and bolted in 3.55 gears.

Edit: I almost forgot to mention that the 2.73 gears kind of sucked on the interstate too. Rarely could cruise in 5th gear. Hills meant constantly downshifting and putting the pedal to the floor to try to keep up.

 

Hi, uk owner with a 2.8 t5 !
i wouldnt do it, the car dosnt have enough power, the slightest motorway (highway folks) hill and youl be down changing, or using a heavier right foot either way your moving away from the power band the engines guna stress more, i think youl ruin your gas millage and your car.
My car is an original rustbucket getting 25mpg easy on a cruise.

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Ok I’ll hang fire for now and see how it goes!