I was thinking about changing rearends or the gears in my rearend, but after reading it seems too complicated. I have an '86 Regal Limited w/ 307 crate motor, 5A heads, A5 intake (I think), Edelbrock 650cfm (#1400), True Duals (no cats), Turbo 350 Trans rebuilt last year when the 307 crate motor was put in. Over the past year since engine and trans install I have NEW....radiator, starter, battery(optima 1000 amp), water pump, fuel pump, gas tank & sending unit, A/C compressor & accumulator, +15" Buick Rally's. I don't want horrible gas mileage, I get about 15mpg street/ 17hwy. I won't be racing this car because I feel the engine isn't made for it and I don't wanna be embarrassed. But I do wanna have a good Street rod.....I like burnouts and donuts!:Brow: Not much more than that is expected from me. What do you guys suggest as far as a rearend goes for my setup (if u can call it that)? I was thinking that I wouldn't lose too much on gas mileage if I went to 3.42 rearend w/ an overdrive 200R4 trans swap. Since reading more, maybe 3.08 is better? Still kinda clueless. o No: E.P.
I woulden't attempt to do it yourself.(change gears) I changed my gears and thay whine. It would wake it up :3gears: If you are going to change the gears I would go with at least 3.42
If you change transmisions to the 2004R than yes a 3.42 or even 3.73. But if you are staying with the th350 then stick to a 3.08. The 307 runs out of breath at higher rpms. No cam and no heads. The gear change along with a limited slip usually referred to as a posi will be the best improvement for your goals and a 307. Hmnn ok along with an advance curve kit and somebody who can get it dialed in for you. All you need for cool burnouts and donuts is a little low end grunt (with gear & posi) and the 307 has that. I had a 307 with a 2004R and 2.56 gears. I swapped out the whole rear with that from a salvage yard Monte SS. It had a posi and 3.73s. It helped a lot but even with a .67 overdrive it could not use any more gear on the highway. Mileage droped on the highway but was better in town and overall dropped very little. PS With the right pipes I have even heard 307s that sound good. But I bet everybody who reads your post is thinking for the same or a little more money that you must have spent on that crate 307 that you could of had a way better motor. Even for simplicity/originality sake an Olds 350/403. Anyway best of luck.
As far as gear installs go, I'm a very uneducated person. But what I did was go to the junkyard, pulled out a Camaro open 3.08 and labelled everything. I pulled out my 2.41 and installed the 3.08 exactly as I took it out of the Camaro. I filled it up with gear oil and drove without any whine. Maybe I just got lucky but it was pretty easy to do. I don't think I would attempt a posi but who knows.
Don't want a WHOLE lot, just enough Firstly, Thanks for the replies guys. Vern, Whats this advance curve kit you speak of? And I know what you mean about getting a better motor for the same or less money, thats blamed on my youthful ignorance, generally not having anyone to give me direction, and my want to go original....wanted to keep cruise and A/C and stuff. Didn't know then that I would disconnect the computer to use the Edelbrock #1400 carb (650cfm I think). The 307 runs good tho, nice pull, just wanna do donuts and burnout. Um, I thought limited slip and posi were 2 different things. can someone clarify that? I plan swapping tranny's to a 200R4 the same time I get the rearend done, and I was thinking 3.23, or MAYBE 3.42, in order to maybe keep some gas mileage as its already 17mpg highway. And thats w/ stock rear, th350, and Edelbrock #1400 carb. Feedback E.P.
which rear is in the car already 8.5 or 7.5? The simple thing if you go with the 200r4 or 700r4 is swap the whole unit with the 8.5" turbo version. May be apples an oranges, but with the 3.42/200r4 in my 87 turbo engine rpms@60 mph are around 2200 with a 245-50-16 tire and if I drive it like an adult (which isn't easy; car has had some major changes) it gets mid 20's on highway driving.
An advance curve kit is a small kit with springs etc that fits under your HEI coil in cap distributor cap. Its used to change the amount and how fast the timeing comes in on your engine. Factory sets it very conservative and leaves a fair amount of power and crispness on the table. If adjusted on a roller dyno along with carb adjustments people often pull another 20 or more HP and torque out of most any given factory set old carberated v8 engine. I am no tuneing guru so thats about the limit of my knowlege in that area. I am suggesting you look into finding a shop or someone who can do it for you even if they don't have a roller dyno to measure your gains. It can be an inexpensive way to get a better running more powerfull motor without having almost anything (a couple dollars) in hard parts. Sometimes their is even gains in mileage. On the downside to much timeing/advance and it can get harder to start and or can require a little more octane in really hot weather to avoid pinging or detonation when under heavy load. Limited slip and posi are actually two different things but a limited slip rear is often generically referred to as a posi. For a street car you want an actual limited slip rear unit and not a full time two wheels always driveing rear. Happy motoring. :3gears:
Hey thanks for the info on the advance curve kit, I'ma look into that. About the rear, why don't I want a full time two wheels always driving rear? Gas mileage? And how do I tell? What do I call it, just a limited slip rearend? and Will both tires spin when I do a burnout w/ a Limited Slip rear? I am aware while typing this that I sound like a complete (searching for right word) ....newbie I guess, but I appreciate ur insight and patience. E.P
A true posi like a detroit locker or something always drives or turns both wheels at the same rate. Its not very street friendly as it is always tearing up a tire as you go around a corner. It also tends to want to push the car straight even when you are turning the wheel to go into a curve. They are generally noisy and make your car suspention become non road compliant when trying to turn especially on uneven pavement. They have their benefits but generally are not as well suited for regular street duty. A limited slip will allow a limited amount of slip to one wheel so that both wheels don't have to turn the same number of turns when going around a corner. One drives the car the other rolls freely. When doing a burn out if one tire has a lot more traction than the other the differential will alow the engine to turn over one tire maybe a revolution before forceing the other to be driven or turned over. So yes both tires will still spin during a burn out. A limited slip differential is even more sophisticated as it will also depending on traction send a different and varying amount of the available engine torque to a each wheel so that each wheel can be positively driven. It divides the available power between the two wheels depending on traction. Eaton makes a quality limited slip differential and has good info & pics on their site.
