Put an IS-F differential in a ISx50…
07-07-08, 08:38 PM
#20
Tech Info Resource
iTrader: (2)
07-07-08, 08:47 PM
#21
Tech Info Resource
iTrader: (2)
07-08-08, 06:40 AM
#24
Lowering your final drive ratio could easily reduce your city mileage as much or more than it raises your highway mileage. When I swapped my ring and pinion in my S2000 to go from 4.10:1 to 4.77:1, my city mileage went from 19 to 24 (25% improvement) in the city. My highway mileage only dropped from 29 to 26 (10% loss).
I also find it hard to believe an IS-F differential would only be $1500. I would have expected more like $5000. Even if it was only $2000 installed, how many miles do you think it would take to make that up in fuel savings if you get 5% better mileage? My calcs show that you would have to spend at least $40,000 on gas before a 5% savings will break even on the $2000 modification.
I also find it hard to believe an IS-F differential would only be $1500. I would have expected more like $5000. Even if it was only $2000 installed, how many miles do you think it would take to make that up in fuel savings if you get 5% better mileage? My calcs show that you would have to spend at least $40,000 on gas before a 5% savings will break even on the $2000 modification.
07-08-08, 09:53 AM
#27
Pole Position
ISF diff. 41110-53270 Lexus' MSRP = $2,132.95
Like lobux says, it will not bolt in. It's completely different. The 350 and ISF share the same rear subframe but the 250 doesn't.
Like lobux says, it will not bolt in. It's completely different. The 350 and ISF share the same rear subframe but the 250 doesn't.
Last edited by IS350jet; 07-08-08 at 10:03 AM.
07-08-08, 10:11 AM
#28
Here is my 2 cent. I dont think he meant literally changing to IS-F diff. I think he meant changing to the same gear ratio as the IS-F diff. Much cheaper in that sense.
You dont have to change the diff to get different ratio. You can change tire size to get the same result.
My Z28 originally had 3.73 but when i blew it out they put in a 4.10 because of a TSB they recommended it. Like Gernby said you lose certain things and gain others. I lost mileage 19 city to 14 city but gain hwy 22 to 24. I also gained a couple tenths at the strip.
Just an FYI for the non-gear heads. if the number gear ratio goes up the lower the gearing.
You dont have to change the diff to get different ratio. You can change tire size to get the same result.
My Z28 originally had 3.73 but when i blew it out they put in a 4.10 because of a TSB they recommended it. Like Gernby said you lose certain things and gain others. I lost mileage 19 city to 14 city but gain hwy 22 to 24. I also gained a couple tenths at the strip.
Just an FYI for the non-gear heads. if the number gear ratio goes up the lower the gearing.
07-08-08, 10:35 AM
#29
Here is my 2 cent. I dont think he meant literally changing to IS-F diff. I think he meant changing to the same gear ratio as the IS-F diff. Much cheaper in that sense.
You dont have to change the diff to get different ratio. You can change tire size to get the same result.
My Z28 originally had 3.73 but when i blew it out they put in a 4.10 because of a TSB they recommended it. Like Gernby said you lose certain things and gain others. I lost mileage 19 city to 14 city but gain hwy 22 to 24. I also gained a couple tenths at the strip.
Just an FYI for the non-gear heads. if the number gear ratio goes up the lower the gearing.
You dont have to change the diff to get different ratio. You can change tire size to get the same result.
My Z28 originally had 3.73 but when i blew it out they put in a 4.10 because of a TSB they recommended it. Like Gernby said you lose certain things and gain others. I lost mileage 19 city to 14 city but gain hwy 22 to 24. I also gained a couple tenths at the strip.
Just an FYI for the non-gear heads. if the number gear ratio goes up the lower the gearing.
Either way, going from a 3.9x to a 2.97 in a car that weighs over 3200 lbs and makes barely 200 at the crank is a waste of time. My buddy did it in his Firebird because he does an NY to FL run doing 120-140 and likes to hold on to his gas mileage. But that car had torque, unlike an IS250.
07-08-08, 11:26 AM
#30
Kind in mind someone order my 1991 Z28 but they didnt buy it. It is a rare police package in a civilian car. There were only about 1500 built for that. I have been clocked at a top speed of 168. It has no speed limiter and all the goodies of a police package without the lights and sirens!
What sucks is when i have to take it in I have to remind my mechanic that so when he orders parts. broke my mechanics foot because of a fuel tank. He order a stock and mine is about 1 gallon bigger. He put the straps on and it slipped out of the straps.
Enough about that... I agree change the gearing will make the car boog on the street. I wouldnt recommend it
Too bad they dont make a over-under system like they do for trucks. 