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cellblock_g
11-13-2009, 09:11 PM
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.

cellblock_g
11-13-2009, 09:20 PM
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.

Nothingface5384
11-13-2009, 09:25 PM
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

gsgns4me
11-13-2009, 10:13 PM
One of the "G" codes on the RPO label should translate into the ratio with a GM parts manual.

monzaz
11-13-2009, 10:21 PM
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:

monzaz
11-13-2009, 10:24 PM
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

cellblock_g
11-13-2009, 10:54 PM
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.

Bad Boattail
11-14-2009, 05:27 AM
Model year 1985 LeSabre:
2.73 for petrol cars, 2.93 for diesels :TU:!

cellblock_g
11-14-2009, 08:43 AM
Model year 1985 LeSabre:
2.73 for petrol cars, 2.93 for diesels :TU:!


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?

Nothingface5384
11-14-2009, 03:54 PM
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

LARRY70GS
11-14-2009, 04:50 PM
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?

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

monzaz
11-15-2009, 09:59 AM
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

cellblock_g
11-18-2009, 09:08 PM
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...

cellblock_g
11-18-2009, 11:12 PM
oh and forgot to mention i would probably want a posi

LARRY70GS
11-19-2009, 11:26 AM
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?
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.

cellblock_g
11-20-2009, 09:21 PM
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.

LARRY70GS
11-21-2009, 04:10 PM
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.

Mark Demko
12-20-2009, 07:51 AM
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:

cellblock_g
04-19-2010, 12:03 PM
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

cellblock_g
08-12-2010, 09:24 AM
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

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.

LARRY70GS
08-12-2010, 10:56 AM
The problem with the 307 is that it runs out of breath so early. The 307 in my 86 Regal would literally stop pulling at 3500 RPM. Putting higher numerical gears won't help that engine. It doesn't breathe at higher RPM.

cellblock_g
08-12-2010, 12:34 PM
The problem with the 307 is that it runs out of breath so early. The 307 in my 86 Regal would literally stop pulling at 3500 RPM. Putting higher numerical gears won't help that engine. It doesn't breathe at higher RPM.

I understand a 307 will never be fast, you don't need to remind me. I don't plan on drag racing or running 110 MPH.

I am trying to keep the car from downshifting more than it needs to on hills, since I live in a hilly area. At 70 MPH with 2.73 gears, my car is barely turning 1600 RPM. It is especially slow in the 45-60MPH range with the lockup engaged. Even a slight improvement is worth the money in my book.

Another problem with the 1985 and newer 307 is the new heads that further castrated an already gutless motor. Had I known this I never would have bought the current car. The 1983 I had in high school was no speed demon either, but it would literally run circles around my current car. It literally runs as smooth as my 2008 Mustang, but very poor acceleration when compared to the older 307 motor.

LARRY70GS
08-12-2010, 05:29 PM
I understand a 307 will never be fast, you don't need to remind me. I don't plan on drag racing or running 110 MPH.

I am trying to keep the car from downshifting more than it needs to on hills, since I live in a hilly area. At 70 MPH with 2.73 gears, my car is barely turning 1600 RPM. It is especially slow in the 45-60MPH range with the lockup engaged. Even a slight improvement is worth the money in my book.

Another problem with the 1985 and newer 307 is the new heads that further castrated an already gutless motor. Had I known this I never would have bought the current car. The 1983 I had in high school was no speed demon either, but it would literally run circles around my current car. It literally runs as smooth as my 2008 Mustang, but very poor acceleration when compared to the older 307 motor.

Sorry if I seem to be beating a dead horse:laugh: , but I had an 86 Regal with that engine, and I despised it. Mine had the 200C with a 2.41 rear. There were several things I did that made a bit of a difference. I discovered that my timing was a bit retarded. My engine had the electronic spark timing, and there was a specific way to set the timing. The 4 way electronic connection had to be disconnected to return the engine to base timing. Not sure if the 85 is the same, but worth checking since you mentioned that your engine seems to be slow even for a 307. Another thing that made a difference was installing a chip that delayed the torque converter lock up as well as providing a faster spark advance curve. Also, I replaced my catalytic converter with a more modern high performance one. That seemed to help throttle response on the highway immensely. Just some things you might want to consider before changing gear ratio.

BTW, I believe the torque peak on that engine is about 1800 RPM, so your cruising RPM is pretty close at 70 MPH. I think if you could put the lock up on a switch so that you could manually select lock up would also help alot. You'd gain 150-200 RPM with just that. Like I said, just some things to think about.:)

cellblock_g
08-12-2010, 06:28 PM
Sorry if I seem to be beating a dead horse:laugh: , but I had an 86 Regal with that engine, and I despised it. Mine had the 200C with a 2.41 rear. There were several things I did that made a bit of a difference. I discovered that my timing was a bit retarded. My engine had the electronic spark timing, and there was a specific way to set the timing. The 4 way electronic connection had to be disconnected to return the engine to base timing. Not sure if the 85 is the same, but worth checking since you mentioned that your engine seems to be slow even for a 307. Another thing that made a difference was installing a chip that delayed the torque converter lock up as well as providing a faster spark advance curve. Also, I replaced my catalytic converter with a more modern high performance one. That seemed to help throttle response on the highway immensely. Just some things you might want to consider before changing gear ratio.

BTW, I believe the torque peak on that engine is about 1800 RPM, so your cruising RPM is pretty close at 70 MPH. I think if you could put the lock up on a switch so that you could manually select lock up would also help alot. You'd gain 150-200 RPM with just that. Like I said, just some things to think about.:)

Do you honestly think quicker gears will be no improvement at all? Even if the car can move better up to 3500 RPM I think that would be an improvement.

Funny thing is the car seems ok for normal driving, gets up to speed ok, but when you really step on it there's not much more there. :rant: Or when I need power on the hills it is pretty annoying too.

I think it is the 1985 and newer 7A heads that make the 307 so slow. The 1984 and older motors with 5A heads actually had some snap to them and could breathe much better, and were more close to 150 HP than commonly known.

I would rather keep the car looking original than install toggle switches for lockup, etc, if I ever sell it little things like that scream electrical nightmare. Where was that 4-way plug for the spark timing located?

LARRY70GS
08-12-2010, 06:42 PM
Do you honestly think quicker gears will be no improvement at all? Even if the car can move better up to 3500 RPM I think that would be an improvement.

Funny thing is the car seems ok for normal driving, gets up to speed ok, but when you really step on it there's not much more there. :rant: Or when I need power on the hills it is pretty annoying too.

I think it is the 1985 and newer 7A heads that make the 307 so slow. The 1984 and older motors with 5A heads actually had some snap to them and could breathe much better, and were more close to 150 HP than commonly known.

I would rather keep the car looking original than install toggle switches for lockup, etc, if I ever sell it little things like that scream electrical nightmare. Where was that 4-way plug for the spark timing located?

That sounds just like my Regal. For everyday driving around it was fine, but when you needed that snap, it wasn't there, at all. It's just an anemic engine.

I think the gears will help at low speed and from a dead stop, but they will not help out when you nail it on the highway, or on hills.

The 4 way connector is right by the distributor, you can't miss it. Take a look at the emissions decal on top of the radiator cover. It will describe the procedure for setting the timing.

cellblock_g
08-13-2010, 10:08 AM
That sounds just like my Regal. For everyday driving around it was fine, but when you needed that snap, it wasn't there, at all. It's just an anemic engine.

I think the gears will help at low speed and from a dead stop, but they will not help out when you nail it on the highway, or on hills.

The 4 way connector is right by the distributor, you can't miss it. Take a look at the emissions decal on top of the radiator cover. It will describe the procedure for setting the timing.

Just be glad you didn't have the standard 3.8 V6 with the 2 barrel carb.

Now that was a truly gutless anemic motor, even by 1980's standards. I drove a 83 regal Sedan with this motor for a while in high school. It drank more oil than an old dump truck, took forever just to get up to 55, and really was not that good on fuel with a 3-speed automatic. Choke would never adjust right, guaranteed to stall when putting it in gear after starting it up in the morning. Guaranteed to stall 3 or 4 times given the same scenario in the winter. I despised this car with all my heart.

One of my friends in high school had a 80 something Cutlass Supreme Coupe with this same motor, and it was even worse. We nicknamed it the "Gutless Supreme" The inside of the air cleaner was totally flooded with oil from blow-by. Climb a hill it would smoke. Go down the highway faster than 65 it would smoke. Pass someone on a two lane road (which took careful timing daring and skill) and it would smoke. It smelled like a tar truck going down the road. We even had an old guy in a newer Buick pass us and give us the finger one day because it took off so slow. :pp My regal seemed to mysteriously just make the oil disappear, the Cutless leaked from about every engine crevice known to man. Both cars had barely 100,000 miles on them.

All the V8's from GM during the 70's and 80's were much more reliable than the first Buick 3.8 V6.