Rear end gears

[Grandprixpaul]

Just checked in my service manual for my rear end gear size it says its a gh2 ----2.29 7.5 not to famular on these gears is that really bad withna sbc 350 or going to be ok untill i get new rear end

 

[Intragration]

It's not going to be very much fun, I wouldn't want to drive it this way for very long.

 

[DRIVEN]

I had the same ratio in my car when I got it. No powerhouse (especially with my stock 305) but got 20 mpg. FWIW, a tall gear set like yours is less likely to break. The pinion is larger (more teeth) and has more contact area. It also puts less torque to the axles.

 

[woody31]

x3 i had a 243 and it sucked swapped ina set of 373 and shazam ,,,, 8)

 

[olds307 and 403]

I had a 78 1/2 ton with 2 different sbc 350's with the stock 2.76 gears. I put in a stock Olds 307 Vin Y with 5A heads and killed either 350. I gained .3 in the 1/8 even running out of fuel half track, .6 with a new fuel pump on my CSC. This is when I swapped from 2.56 to 3.42 to 1, which about the lowest you should run with a 3spd trans.

 

[Phoenyx]

Just checked in my service manual for my rear end gear size it says its a gh2 ----2.29 7.5 not to famular on these gears is that really bad withna sbc 350 or going to be ok untill i get new rear end

Depends what you mean by 'bad'. If you mean bad for the engine or anything mechanical, then no it's fine. If you mean 'bad' for performance, then yeah it will not launch very good. But there's no problem running what you have until you can do a gear swap.

 

[Grandprixpaul]

Well thanks for the help guys ,i knew i had to replace but it sound like there going to be good on gas but suck ,so no racing mustangs yet, but i see most guys here run 373 gears are they good for highway use with a 350,350 turbo trans. And seams 8.5 is the way to go is it just not worth putting a posi unit into a 7.5 thanks

 

[Peter]

i run 4.56 just because i got an outstanding deal on them that i couldnt turn down. we'll see how much i like them after this summer

 

[Phoenyx]

I bought what I thought was 3.73s, but every gear calculator I try tells me they are 4.11s. From what I hear there isn't much difference between the two. I runs a tire very close to stock OD, and I can say it's not very highway friendly. At about 90kmh (about 55mph) I'm sitting close to 3000RPMs (approx.). My car sees very little highway time so that's OK with me. If you have to take yours on the highway, you might not want that much gear. Also, the OD of your rear tires makes a big difference in your final gear ratio too.

People say a 7.5 will hole up on street tires. But I can personally say I have broke 4-5 with stock 305s and a 301 (but they were old and abused rears). A rebuilt one would probably hold up. But getting a rear end rebuilt (at a shop) is expensive. It would be worth the extra cash to find an 8.5 that needs rebuilding and go with that. Or if you have the cash go for a bolt in 9" or 12 bolt.

 

[CHRIS.O]

Your fuel mileage may actually suffer. Sometimes the lowest numerical gear is the worst for everything. I bet if you switched to a 3.23 your mpg would improve, as well as performance.