Rear-end, what will support my Olds 455?

[82-T/A]

Hey guys,

I've got a 1973 Oldsmobile Cutlass Supreme with a 350 and a Th-350 in it. My plan is to drop in my built-up 1969 Oldsmobile 455 big block. The engine is fairly hot... I'm expecting in the neighborhood of 380hp, and about 550 foot pounds of torque.

I'm going to bolt it up to a Th-400, and I'd like to use a 12-bolt rear-end since I just don't think the 10-bolt will be able to handle the torque and abuse that intend to dish out.

With that said... what are some cars in the junkyard that HAVE 12-bolt rear-ends that I can snag and simply "bolt in" to my 73 Cutlass?



Thanks!!!

[73CS]

I think it kind of depends on how much traction you are going to have. Is it going to hook up? I think the rear-ends on these cars are stronger than people give them credit for. If you are running street tires you will probably bust them loose and start spinning. At that point it doesn’t matter if you are spinning them with 250 foot pounds or 550 foot pounds. When I was young I beat the crap out of these cars, trashed a lot of transmissions, but never once broke a rear end. Just my .02 I am sure someone else will chime in. Zodiac Blue has a big block drag car and I think he has a 10 bolt. He could probably give you some info.

I see you have a Fiero, I just sold my 87 GT earlier this year, sure do miss it, but times are hard, and I chose to keep the Cutlass.

[82-T/A]

I think it kind of depends on how much traction you are going to have. Is it going to hook up? I think the rear-ends on these cars are stronger than people give them credit for. If you are running street tires you will probably bust them loose and start spinning. At that point it doesn’t matter if you are spinning them with 250 foot pounds or 550 foot pounds. When I was young I beat the crap out of these cars, trashed a lot of transmissions, but never once broke a rear end. Just my .02 I am sure someone else will chime in. Zodiac Blue has a big block drag car and I think he has a 10 bolt. He could probably give you some info.

I see you have a Fiero, I just sold my 87 GT earlier this year, sure do miss it, but times are hard, and I chose to keep the Cutlass.


That's interesting that you say that, because I didn't really consider that. Yeah... my ultimate goal with this 73 Olds Cutlass Supreme is to build a car that basically LOOKS stock.

This is it now:

http://www.pontiacperformance.net/CarImages/73_Olds/73_OldsMain.jpg

I plan on either repainting it this color (the factory burgundy color), or painting it the factory blue color that was offered that same year. This car was originally pea green, but it was repainted in this color (in the spirit of the factory burgundy) before I bought it.

I'll more or less keep it totally stock, but maybe add a few features that mine doesn't have like rear-defog, whatever... maybe go with slightly wider tires in the rear if I can (but still use the factory hub cabs... I have a spare set too), and then drop my Th-400 and my 69 Olds 455 big block in it and just tear around town in it.

I might take it to the track, simply to see what it will run, but not with the intent on competing with it. I want to build a nice street car.

Ideally, I might even go with those electronic cut-outs so I can keep a set of rather quiet and calm mufflers when I just want to drive around, and then switch to a more aggressive exhaust at the flip of a switch.

I'm debating whether or not to rebuild a switch pitch too...

[82-T/A]

I see you have a Fiero, I just sold my 87 GT earlier this year, sure do miss it, but times are hard, and I chose to keep the Cutlass.



Oh yeah, I forgot to respond to the Fiero statement.

Yeah, it was my first car. I bought it in 1995 when I was about ~17 years old. I saved up working at Mc.Donalds and CompUSA. ~13 years later, I still have it. I'm never going to get rid of it. It just sits in my garage now. I've blown the motor and rebuilt it, and then trashed the cam. It's got 150k miles on it now, but it's still in decent shape. The interior is in excellent condition and the paint, for the most part, is still pretty decent. There's no rust on the frame anywhere either. I've been buying parts for it for the past 4-5 years in hopes of one day getting the time to totally re-do it. I've got something like 5 grand in brand new parts for the Fiero just sitting in boxes. Completely new suspension components, everything from new springs, shocks, struts, to spring isolators, rubber bumpers. All new tie rods, bushings... all new brake components, stainless steel brake and fuel lines, new coolant lines for the heater core, new A/C compressor... just everything you can imagine... all sitting brand new in boxes for when I can get around to it.


This was it in 1998:
http://www.pontiacperformance.net/CarImages/87_FieroSE/FIERO_Main.jpg


And this is it now:
http://www.pontiacperformance.net/CarImages/87_FieroSE/87_Fiero_1_lrg.jpg

http://www.pontiacperformance.net/CarImages/87_FieroSE/87_Fiero_2_lrg.jpg



That's my 69 Olds big block in the 2nd pic on the far right.



But yeah, I could never let myself sell this car.

They only made 1,800 1987 Fiero SE / V6 cars back in the day, and... even though that doesn't make it worth more... it's still pretty rare and uncommon. I went to a huge Fiero show in Daytona back in March where there were over 100 Fieros... I was the ONLY one with an 87 SE / V6. It's basically identical to your 87 in every way, with the exception of the fastback body panels. Interior and engine layout are all identical though. It's very rare that someone gets the opportunity to keep their first car, so I have to make sure I hold on to this.

[73CS]

Hold on to it, I had mine for 12 years. I like the big block, I have one completely disassembled, waiting on some spare cash to start the rebuild.

[442MUCH]

My 455 puts out about 435 HP and I have a 10 bolt rear-end. I''ve never had an issue in the 30 years that I've owned her. I've read that if you plan on drag racing the car everyday for the next five years and you have a 10 bolt, you MIGHT have a problem at the end of the 5 years. "Might".

The 10 bold is a very sturdy, tough rear end. I suppose that anything is possible, but in my opinion, you'll be OK with the 10 bolt.

[W451973]

First, there are no 12 bolts that will 'bolt' into your car unless you buy an aftermarket one. Second, your 8.5 10 bolt will hold up just fine as long as it's built right. 1- Weld the axle tubes to the center housing. 2- Eaton carrior with 800 lb springs. 3- Good name brand ring & pinion such as Precision or Richmond. 4- Good set of axles like Moser. Do this and it will handle anything you throw at it. Then you'll just have to work on the rest of the suspension.

[82-T/A]

Thanks guys, I appreciate it. I did a couple of searches and I can't really find anyone that offers a direct bolt-in 12-bolt for our specific years of the "A" body. But I guess it should make sense that if it can support a 455 in stock form, I should still be ok.


Thanks!

[zodiacblue442]

duplicate post.

[zodiacblue442]

My 75 Cutlass drag car has a basically stock 10 bolt rear end with 4.10 posi. Gears are Richmond and axles are Moser. The GM 8.5" 10 bolts are incredibly strong. You won't have a problem with a 10 bolt and stock or a little wider tires. A 12 bolt rear end was not available for a 73-77 Cutlass. I don't know of a 12 bolt that would be a direct bolt in.

The drag car is a strip car only. It will sit in the water box and roast the tires all day with the engine roaring at 5,500 rpm, and they are P275 size "sitcky Mickeys". The engine is a 68 Toronado 455 bored out to a 461 with a few high performance goodies, and the transmission is a long shaft TH-400 with racing clutches, TCI Streetfighter torque converter (approx. 3,200-3,400 rpm stall), and auxillary trans. fluid cooler. I've never had the car on a dyno but my guess is the engine is putting out an honest 400 to 450 hp at the rear wheels. Attached is a pic. of the abuse the rear end is taking. I love the smell of tire smoke! :p

http://i69.photobucket.com/albums/i58/zodiacblue442/burnout_2.jpg

http://i69.photobucket.com/albums/i58/zodiacblue442/burnout_1.jpg

Regarding the color of your car... I have a cranberry red Supreme and a zodiac blue 442 so I think the cranberry or blue would be excellent choices to paint your car. The cranberry paint code is 74 and the zodiac blue paint code is 26. Both are factory colors for 1973. Oh yeah, I'm biased! :p

Good luck with your Olds!

[73431Cutlass]

I have a basically stock 10 bolt in my 73. I built it in 90 when my rear in my 76 came apart (center pin bolt broke so the pin slid out) It has a GM posi unit and 3.73 gears. I have been thru 4 motors and 5 transmissions since 1989 and this is the same rear in my 76 and now my 73. Both cars had medium built big blocks. I treat it nice now as I am older and wiser, but when I was young.... Every chance I had I was frying the tires....

[rcktpwrd]

I had the original 10 bolt rear in my '76 for a long while. After I dropped in a mild 455/th-400 I put 3:73 gears and a posi unit in there. It worked well for me.
Then after the 455 blew up I built a 468 that makes 540hp and 575lb-ft. The rear held up fine with plenty of street and track time using ET Street tires... Since the car is running in the 11's I wanted to upgrade to a nearly bullet proof rear so I put in a 9"
I could have upgraded the stock rear end to get rid of the c-clips and went with stronger axles, but the cost wasn't that much more to just swap the entire thing out...

[ragz442]

I agree the factory 8.5" 10 bolts are strong, but Drive Train Specialists out of Ionia Mi. offers a 12 bolt assy for the 73-77's with disc brakes. They advertise in the CruiseNews and have a pic of it, it looks like a sweet diff. I'd have to hit the lotto before I could afford one, but I thought it was cool that they made the effort for our years anyway.
www.drivetrainspecialists.com

[oldsmeister]

I hate to get off topic again but I always liked those Fieros too. I also love the Cadillac 4.9. Does that sound like a match made in heaven or what? It happens more than you may think.

http://www.fieroaddiction.com/caddy49b.html


I also think the 10 bolt is pretty strong especially when built up with quality parts, but Currie Enterprises will build a 9 inch for just about any car.

[82-T/A]

Thanks guys, I really feel confident about keeping this 10 bolt now. I don't know if it's a posi or not, haven't really gotten down there to check, but I would doubt it since it's a base Supreme with the 4bbl 350 in it.

It whines a little bit too... which is very similar to the whine I get in my Solstice (which does have limited slip)?

How difficult is it to service the rear-ends of these? I assume it's nothing more than removing the rear pan, and refilling it from the top (I believe there is a plug on the casing, right?

Do I just measure the fluid I take out, and then put the same amount back in?



Thanks for the paint codes Zodiac Blue... yeah, I'm really digging the blue color a lot. The color I have now is cool too, but I think I'm looking for something a bit more exciting (like the blue you have).


Oldmeister, yeah, I'm very familiar with those 4.9 swaps. The 3800 is also very common. Like I had mentioned, I have a friend that has two Citations, one with an 3800SC and one with a 4.9 Caddy V8. The Caddy V8 easily drops in and you get low to mid 14 second quarter mile performance on a stock 4.9 Caddy motor. There's a ton of performance parts too that'll get it well into the 12s if you so desired.

[zodiacblue442]

It whines a little bit too... which is very similar to the whine I get in my Solstice (which does have limited slip)?

How difficult is it to service the rear-ends of these? I assume it's nothing more than removing the rear pan, and refilling it from the top (I believe there is a plug on the casing, right?

Do I just measure the fluid I take out, and then put the same amount back in?

Thanks for the paint codes Zodiac Blue... yeah, I'm really digging the blue color a lot. The color I have now is cool too, but I think I'm looking for something a bit more exciting (like the blue you have).


Rear end "whine" is more common with posi rear ends, but I suppose if a conventional rear end ring and pinion is really worn, it will cause a whine too. If you can find the code on your axle tube (front of the tube, passenger side, about 4 to 6 inches away from the center differential) it will tell you if the rear is a posi or not and what the ratio is. In the case of your 73, if the code is AC, it will be a conventional rear end with 2.73:1 gear ratio. That is the standard rear for 73-74 Cutlass. If the code starts with a C (for example CC) it will be a posi. CC is a 2.73 posi. Get the code and I or someone else on the list can tell you what it is.

Don't worry about how much fluid you take out. To change the fluid, take the diff. cover off (have a big pan because the old gear oil dumps everywhere). Gear oil is a mess to clean up! :mad: Reseal with a new gasket. There is a plug in the diff. case. Fill the rear end with new gear oil. Stick your pinky finger in about a half inch into the hole where the plug goes. If the end of your finger has oil on it, the rear end is full. Overfilling where the oil starts running out of the hole isn't a big deal but if overfull, the gear oil may start blowing out of the differential vent when you drive the car which can be a little messy. Remember if you have a posi., you need to get gear oil with a posi. additive or you can buy the additive separate and mix it with the oil yourself.

The zodiac blue color is a really pretty medium silver blue. It also has hints of red in it. In different light, the silver and red "highlights" really show up in the paint. It is a very unique color.

[W451973]

A properly prepped 10 bolt will take just about anything you can throw at it. Plus they weigh less then a 9 inch or 12 bolt and use less horse power to turn. A 'properly' prepped 8.5 will hold up to a hi-torque heavy car, into the 10's. GN guys do it all the time.

[oldspeed_442]

the 72-xx? corprate 8.5 ten bolts with the bolt in axles built right will take everything, if not more, than an o type 12 bolt will, and probably close if not the same as a chevy 12 bolt... and there is no bolt in 12 bolt rear that fits a 73-77, so check your rear see which one it is. the c-clip rear axle tubes neck down out by the backing plate flange, and the bolt in axle ones have a straight tube.

[73CS]

See if the trunk has one of these.

[73CS]

Off topic again, I wish I had held on to this, was my daily driver for twelve years, I think the chevy V8 swap is the way I would have went if I had the money, the V6 5-speed was pretty fun though.

[Workingspy]

Hey guys,

I've got a 1973 Oldsmobile Cutlass Supreme with a 350 and a Th-350 in it. My plan is to drop in my built-up 1969 Oldsmobile 455 big block. The engine is fairly hot... I'm expecting in the neighborhood of 380hp, and about 550 foot pounds of torque.

I'm going to bolt it up to a Th-400, and I'd like to use a 12-bolt rear-end since I just don't think the 10-bolt will be able to handle the torque and abuse that intend to dish out.

With that said... what are some cars in the junkyard that HAVE 12-bolt rear-ends that I can snag and simply "bolt in" to my 73 Cutlass?

Thanks!!!

Hey how are you, it's nice to see another fast 73 comming along. I just put a 9" from quick performance in mine and it is a beautiful piece. Here is a link to my build up, if you have any questions about the 73 there is a good chance I have just been threw the same thing. Let me know if I can help as all my stuff is being setup for all out racing and strength, I also have a bunch of 73 and 455 parts laying around. Good Luck man.

Build
http://72.22.90.30/phpBB2/viewtopic.php?t=54023

Parts for Sale
http://www.73-77olds.com/forums/showthread.php?t=1942

Cheers,
Evan

[82-T/A]

Thanks Evan, I appreciate the link. I'm going to check out your project.

I'm going for a sleeper look. I think I'm going to keep the car looking mostly stock, but have my sick 455 in it. It should be a lot of fun. Obviously it'll have major problems hooking up off idle, but it should still have plenty of pull once it does hook up.

My goal really, is mid 14s I think... that's what I'm hoping to achive. I figure I can probably do this with a relatively stock 73 suspension, and a 400hp/550lbs of torque 455, on basically street tires.

Am I crazy to think I can get mid 14s out of it?

[Workingspy]

Thanks Evan, I appreciate the link. I'm going to check out your project.

I'm going for a sleeper look. I think I'm going to keep the car looking mostly stock, but have my sick 455 in it. It should be a lot of fun. Obviously it'll have major problems hooking up off idle, but it should still have plenty of pull once it does hook up.

My goal really, is mid 14s I think... that's what I'm hoping to achive. I figure I can probably do this with a relatively stock 73 suspension, and a 400hp/550lbs of torque 455, on basically street tires.

Am I crazy to think I can get mid 14s out of it?

Sounds like it will be a fun build and car, good luck with it all. As for your times I don't really know what to say. I am hoping that I am in the low 12's but I would not be supprised if I was around 14 for a while as i learn.

Cheers,
Evan

[rcktpwrd]

Thanks Evan, I appreciate the link. I'm going to check out your project.
I'm going for a sleeper look. I think I'm going to keep the car looking mostly stock, but have my sick 455 in it. It should be a lot of fun. Obviously it'll have major problems hooking up off idle, but it should still have plenty of pull once it does hook up.
My goal really, is mid 14s I think... that's what I'm hoping to achive. I figure I can probably do this with a relatively stock 73 suspension, and a 400hp/550lbs of torque 455, on basically street tires.
Am I crazy to think I can get mid 14s out of it?

Before my current engine, I had a mild/stock 455 in my Cutlass. It was a stock rebuild that I add and Edelbrock Performer intake, cam and carb too, along with headers and 2.5" dual exhaust. I also put 3:73 gears and a posi in the stock rear. With M/T ET Street 28x11.5 tires it ran 13.30's all day long.
The factory suspension and rearend should hold up just fine as long as everything is in good working order.

[Workingspy]

Before my current engine, I had a mild/stock 455 in my Cutlass. It was a stock rebuild that I add and Edelbrock Performer intake, cam and carb too, along with headers and 2.5" dual exhaust. I also put 3:73 gears and a posi in the stock rear. With M/T ET Street 28x11.5 tires it ran 13.30's all day long.
The factory suspension and rearend should hold up just fine as long as everything is in good working order.

After my moment of truth hopefully at the start of next month, I should be able to answer that question with a little more specifics. Believe me I am dying to know that answer also, however if I am not happy I have another much stouter engine in waiting.

Cheers,
Evan