well as far as gas milage im getting about 10mpg town and maybe 14to 15 highway ..i know the v-8 is going to hard on gas but im thinking that with a lower gear im not going to have to push the gas peddle down as far to maintain say 65mph.. looks to me the farther you push that pedlle the more gas your going to use ..even still if a gear change don't help improve mpg and it just stays the same then at liest i will have a better gear for my engine set up with better off line power.. if there isnt much i can do about my mpg then i;ll still want the better take off power so with that said , you guys suggest a 3.08 through maybe a 3.25 ratio.. if those are my only gear choices then back to my first question , what car and maybe where to look to find a complete rear end that will bolt in with no mods...thanks guys for helping ..this sight rocks..glad i found it...
85 monte carlo ss rear end
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The early 7.5's use the cone style, but the one I have from a MC SS is a Gov Lok. F bodies also used the Gov-Lok as well. I also have a cone style 2 series carrier from a 1978 Cutlass, so both were used, but the only ones I have seen with the 3.73's is the Gov Lok. The 2 series cone diff will be going in the Cutlass with a spacer soon as it is almost uncontrollable as a 1 wheel burner right now...
As for what car to get the axles from, you need to have the Service Parts ID codes so that you can look at the sticker to see what the car came with. Here are some of them: Posi is G80, 3.23 is GU5, 3.08 is GU4, and 3.73 is GT4. I do not have a listing in my 1985 FSM, so maybe someone else can list it. Oh, and a 7.5 axle is coded as a G89 while a 8.5 axle is coded G87.
As for what car to get the axles from, you need to have the Service Parts ID codes so that you can look at the sticker to see what the car came with. Here are some of them: Posi is G80, 3.23 is GU5, 3.08 is GU4, and 3.73 is GT4. I do not have a listing in my 1985 FSM, so maybe someone else can list it. Oh, and a 7.5 axle is coded as a G89 while a 8.5 axle is coded G87.
my 87 SS has the stock axle in it and it's a cone type. plus i checked alldata awhile back and they only show the eaton and auburn types, not the gov-loc.
Whoever told you that doesn't know what he's talking about. :?hddave1 said:
Granted, going from 2.41 to 3.xx gearing will do wonders for performance, but at the expense of gas mileage, especially on the highway.
Moreover, your theory about throttle position is backwards, if anything lower gears, (higher numerically), would require more throttle to keep RPM up to maintain speed. More engine rpm=more frictional loses=more fuel consumption.
With the non-OD TH350 trans I wouldn't go any higher than a 3.08 ratio if fuel economy is a concern. Forget about 3.73, the engine will be screaming on the highway and so will your wallet.
Unfortunately, G-body 3.08 rears are rare. The gearing in your El could be changed, but that costs big bucks and qualified installers are hard to find.
I think I'd give the engine a good going over first. A 250 horse crate engine in proper tune and 2.41 gearing should be able to deliver around 15 city/20hwy MPG no problem. What carb are you running, where is the timing set at, is the exhaust restricted, catalytic converter clogged? These are things I'd check out before swapping in a new rear.
Quadra-Jets are best for fuel ecomony with their small primaries and huge secondaries for WOT blasts, also a free flowing dual exhaust will help fuel economy and power.
i have a 3.73 gear in my car and hate it... i mean around the city its plenty fun but on the highway!?!? forget it.....
i only have a 3spd trans... it wouldnt be so bad if i had 2.73s...
i only have a 3spd trans... it wouldnt be so bad if i had 2.73s...
Your city MPG improves with more gear to a point. I get 2 mpg better in the city (16 mpg vs 12-14) with 3.23's as compared to 2.41's. It requires MUCH less throttle to get it off the line, and that is what is important in a car that sees constant stop and go driving. Now, 3.73's would be a bit much, and counter productive. I probably sacrificed some highway mileage with that gear, but highway mileage is pretty worthless if you live in an urban or suburban area like I do. I rarely ever even see 65mph, maybe once a week. For me, a 3.23 with a TH 200 4R is the best setup as it gives you 33% overdrive, knocking the gears back to a 2.16 in high gear. I ran it with the TH200 4R and 2.41 and got 12-14 mpg city. It was too much of a good thing. The compound ratio for that setup is a 1.61:1 !!! WAY too low to pull with my engine. Heck, the 231 V6 got 14 city and 29 highway with the 2.41 axle. That is because a 2.41 is great for highway cruising, but useless around town. I had to bury my foot in it to get it out of it's own way. You gotta remember that back when GM built these cars, they were using highway MPG for bragging rights, and so they tuned their cars to be optimized at the double nickel.
I can remember 12 years ago taking the car up the Sunshine Skyway bridge with the V6 and 2.41's. I had a technique: Top it out at it's max speed of 79 mph, and hold it to the floor the whole way to the top. By the time you crested the bridge, it was going 40-45mph! This is why high altitude G bodies with the 231 V6 came with the optional 3.23 gears. It was useless with the 2.41. I may, one day upgrade to the 3.42 gears for better performance (were I to find them cheap enough), but I am really happy with the 3.23's. I only need to add a posi diff to the rear end to make it perfect. It must also be added that my engine makes 380 ft lbs of torque at 1800 rpm, and 400+ from 2200-4500 RPM. It does not need much gearing to get it going, but it does need some.
I can remember 12 years ago taking the car up the Sunshine Skyway bridge with the V6 and 2.41's. I had a technique: Top it out at it's max speed of 79 mph, and hold it to the floor the whole way to the top. By the time you crested the bridge, it was going 40-45mph! This is why high altitude G bodies with the 231 V6 came with the optional 3.23 gears. It was useless with the 2.41. I may, one day upgrade to the 3.42 gears for better performance (were I to find them cheap enough), but I am really happy with the 3.23's. I only need to add a posi diff to the rear end to make it perfect. It must also be added that my engine makes 380 ft lbs of torque at 1800 rpm, and 400+ from 2200-4500 RPM. It does not need much gearing to get it going, but it does need some.
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