Hello I have a 1985 Buick Le Sabre with 307 V8 and 4-speed automatic. I was wondering if anyone knows the standard rear axle ratio for the car? I checked the RPO codes on the trunk sticker (as I do not have the sales sticker) and they simply indicate that it has the standard axle ratio, with 7.5 inch pinion gear. I'm assuming that it is geared ungodly high judging by my slow acceleration (slow even for a 307, and yes I am familiar with them). I want to upgrade to at least 3.08 or higher. What is interchsngeable between Buick-Olds-Cadillac-Pontiac-Chevy-GMC? And do I need to use something with 7.5 inch gears or can I use the bigger size too (which I can't remember off the top of my head)? Guess my main concern is that my axle shafts will match up too.
And also what can i expect to pay for a good used diff, either Posi or open. Not looking to drag race just want to get some more snap out of an old gutless turd. so 3.08 or higher gears is what i would want.
most likely a 2.56 open end since you got youreself a 307 i'd choose a 3.42 r/p i beleive you can use an 8.5 gearset..just need a spacer...but i would imagine since its a v8car it should already have a 8.6 axle..atleast i'd hope
Well if you have a 7.5 ring gear rear you have to stick with those SIZE gears and posi unit etc. IF you replace the WHOLE rear you can up grade to any B-body rear from ANY RWD GM caddy Chevy Olds Pontiac or Buick. ALL the rear were the same mounting. BUT if you do the 8.5 swap you will need to shorten the drive shaft. You can get the newer 10 bolt 8.5 1990-1996 impala or Roadmaster (they are 30 spline axle rear too) rear for pretty cheap around here for 200-300 with posi and 3.08 3.23 and if your lucky maybe 3.42 tow package option. NO wagon rears they are wider than the sedans. You can also use the 1973-1977 A-body rear in the 1978-1985 B-body also BUT the bolt pattern for the wheel will be 5 on 4 3/4 ...If it is a c-clip rear you can just swap out 8.5 b-body 1978-1985 axle for the 73-77 a-body 28 spline axles and you have your 5 on 5 full size car bolt pattern again. Neat huh? Jim:3gears: :3gears: :3gears:
Oh and if you need a 3.42 corporate 12 bolt that will fit your Lesabre it was from a 1978 Cadillac b-body it would bolt into your car too. Check the classifieds. Jim
Ok I did some RPO code searching and found out it has 2.73's. Part of my problem may be that I need a tranny rebuild too, or at least a fluid change. So if I understand correctly i will need to stick with 7.5" ring gears if I don't want to do any modifaications such as changing axles and shortening drive shafts? Anyone happen to know what the quickest ratios were in the 7.5 inch size? So I guess next question is what will bolt right in (as a full unit or just gear replacement) without having to change axle or driveshaft? Also wondering if the Regal/Cutlass rear ends were typically the same size and will fit in here? Positration would be nice but the main thing I am looking for is just a little more snap.
Yes, thank you, we established that above. Now anyone know quickest ratios in 7.5 inch gears. Or where I can order new ones that will fit?
monzaz will hook you up with the ring and pinion and install kit and posi he'll most likely have the best prices jegs and summit should have them.. randys ring and pinion definatly has them, but theyre overpriced
The quickest, of course, will be the highest numerically. You can go to a 3.73 ratio, and your final drive will still be 2.50:1 because of the .67 OD 4th gear. You can order ring and pinions for the 7.5 from Jegs or Sumitt. http://www.jegs.com/i/Richmond+Gear/836/49-0007-1K/10002/-1
7.5 ratio can go all the way up to 4.56 if you really want...lol You have a 2.73 ratio SO understand that that carrier can only hold 3.08 ratio as a GM gear. If you want a 3.23 3.42 3.73 4.10 4.30 4.56 gear ratio you will have to either get another carrier (posi or open) OR a set of THICK aftermarket gears. Again I can help you with either ways. You carrier will be a 26 spline axle unit. This should give you ALL the info to get the right parts. ALL malibu and regal G-BODY car WILL NOT physically bolt into your le Sabre chassis. The posi and gears fro the inside WILL. YOU can USE a a-body rear differential from a 1973-1977 A-body regal cutlas grand grix malibu etc. as a direct bolt in BUT the wheel bolt pattern will be wrong. And this rear will be a 8.5 NOT a 7.5...That to me is a good thing...lol. But you said you did not want drive shaft mods. A SMALL PRICE TO PAY FOR ALL THE EXTRA STRENGTH YOU WOULD GET. :beers2: give a call I will help you understand. sometimes it is hard to explain it all in a thread.... our use of terms will sometimes confuse each other in what we call certain items in the diff. Jim 330 659 7117
Hey Jim, I think I would be interested in going with a 3.42 or 3.73 and keeping my axles/diff size as is. I still would like to maintain some highway fuel economy. I would even consider 4.11's if the RPM's were low enough at highway speeds. So long as my motor won't be screaming at 3200 RPMs at 70 MPH. (3200 RPM's is pretty much screaming for a stock 307) As I said I am just looking to get a little more snap of of the poor little 307 for now. Any idea what my RPM's at a given speed would be with the above mentioned ratios vs. the 2.73 it has now? So if i understand right I just need a new carrier unit and the gear set, anything else? i would definately appreciate some help as to where to order or pick all this stuff up. ...Dumb question, but will I be able to leave the rear end in the car while having the gears replaced Thank you in advance for your help...
The 200R4 has a .67 4th gear overdrive. Your final drive will be the rear axle ratio multiplied by .67 So, if you went with 4.11's, it would be 4.11 X .67 = 2.75 RPM without converter slip would be = 336/tire height X final drive ratio X MPH Stock tire height is usually about 26.6", so 336/26.6 X 2.75 X 70 MPH = 2431 RPM. Since the 200R4 has a lock up torque converter, that would be your RPM's on the highway at 70 MPH with 4.11 gears out back. The entire rear does not need to be removed to replace the carrier and gears.
If that's the case I would probably just go with 3.42, 4.11 would definately be overkill. Are you sure tire height is 26.6 inches with only 15 inch rims? Standard tires for these cars are usually 215 75R15 or something very close.
A 215/75R-15 will be taller, about 27.7" For our A bodies, most tire heights stock were right around 26.6". My point is that you must take into account tire height when use the formulas I posted.
I doubt a gear change will increase the performance of your 307 as much as you hope it will. My dad had a '90 Estate wagon with the factory towing package, 307 4bbl, and 3.23 limited slip rear, man was that thing a DOG! The engine just wasnt powerful enough even with the 3.23 rear, and it was rated to tow 5000 lbs. It was a whopping 140 hp, and 240 torque. Good running little V-8 but gutless:eek2:
Well being that its a sedan and not a wagon there is some weight savings, plus going from a 2.73 to a 3.23 it should gain a little. I understand the fact that a 307 will not be fast, but I've driven them before and this one is especially slow, even for a 307
Ok so I found this old post archived. Sorry if I'm beating this to death. If I understand correctly, I can install 3.23 or above ring and pinion (keeping the carrier I have now) if I buy thick aftermarket gears, but not the original GM ones? and I have to use ones that say 26 spline right? Because I am seeing a lot of them on jeggs advertised as 27 spline that claim they will fit my car. I believe ringpinion.com says the have the 26 spline. Also are the install kits necessary, or are they a good idea in your opinion? usually they are sold separately.
