at the local pull it yard i found and early 80's elcamino and it has a limited slip rearend. they told me $75 for it and i was just wondering if it is worth it as the rear i have in my 86 cutlass is a peg leg and i cant find a posi unit. thanks
is this rearend worth it?
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allright thanks. i was thinking that posi and limited slip was different but after doing some searching i see they are the same. i am going in the morning to get it. thanks guys
Just be sure that the gears it has are worth your time. Bring a calculator and divide the teeth of the ring gear by the teeth count of the pinion gear. This is stamped on the ring gear and will look something like 41:10 (4.10). If it is lower than a 3.08, it may not be worth your while as a decent gear will require a spacer or a thicker ring gear to work.
well i got the rearend today. after i got home i pulled the cover and counted the teeth. looks like 16 and 41 which should be 2.56. are these gears decent if not can i swap the gears to a better gear? let me know your opinions
just so you guys know i am not going to a track or anything. i want decent mpg and a little power thats all. as far as the car i yanked the 307 and i just put a 305 from an 86 iroc camaro that was tpi but all the tpi was removed and it has an edelebrock performer rpm intake and a edelbrock 600 cab and a 700r4 transmission. just thought you should know all the info for honest opinions on the rearend
Well the 305 didn't make a lot of torque so a lower gear (numerically higher) will help you a lot. Also if you have an overdrive you can stand plenty of gear on the highway. Ideally a 3.73 or better would help you get the most 1/4 mile acceleration out of it and give you decent mileage / rpm on the highway. Only thing is I believe you can only go to a 3.08 with that gear. Except as 85 Cutty says more with spacers. But I don't know how much and how much less than ideal weaker etc useing the spacers are. Maybe he can fill us in. Why did you not keep the tpi? No computer?
garyl24 said:
Are they decent? Depends on what you have for a transmission and what you want to do with the car. My dad's El Camino has 2.56s in it with a 4L60E (700R4) and it actually gets the same mileage in D as in OD. He is on a quest for maximum mileage. If your present gears suck as hard as mine do (2.29), then it is a slight improvement.
You didn't mention whether you want to cruise or race. Take a look at this. It may help you decide if these 2.56s will work for you or not.
http://www.csgnetwork.com/multirpmcalc.html
From what you have posted, I would recommend getting a 3.23 gear installed in that housing before you install it in the car. It will improve around town fuel economy and acceleration at the possible (but not definite) cost of a little highway fuel economy. You will have to buy it new from a company like Richmond gear, or just go to a local rearend shop and have them do it. I have the 3.23 and a Th2004R and like the gearing combination very much. My engine makes decent low end torque, so I really don't need very short gears. It is a huge improvement over the 2.41's that used to be in it! Remember that the gear ratio reflects the effective torque multiplication from input to output. Also, you have to remember that the final drive ratio is a compound ratio, not a standalone number. So, given my car's .67 OD, and 3.23 rear gear, the effective ratio from the input shaft to the axle is 0.67 x 3.23=2.16. Effectively, the engine in my car turns slower than it would have with the TH200c and 2.41's that came with the original V6. The equation for the V6 would be 1.00 x 2.41 = 2.41. So, you can see that by combining the right transmission with the right rear axle, you can gain both acceleration and fuel economy in one package. Also, there is a reason why that Elky does not get better fuel economy in 4th than it does in 3rd. You can cut your cruising speed too much and be out of the effective torque curve of the engine. However, this bit of theory gets into some things I don't understand well enough to condense just yet, like Brake Specific Fuel Consumption ( BFSC). Just think of it this way: With the gearing matched well to the engine, you need less throttle input to accelerate the car and engine (you get more wheel torque via gearing instead of throttle), so you also reduce the need for fuel. Just remember that there is a narrow zone in which this can work. Go too far in either direction and you will hurt fuel economy and/or performance.
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