Hi all,



Recently purchased Vehicle: 71 Olds Cutlass S

Engine:
-66 Toronado 425CI .030" over, 10.5:1 Federal Mogul pistons
-Steel rocker arches for added strength and durability
-Crane lifters and push rods
-Engle racing cam
-New timing chain & gear
-Edlebrock torker intake with new rochester Quadrajet
-Standard HEI ignition
-Cast manifolds, 2.25" exhaust with Flowmaster turbo mufflers


Transmission: TH400 with 2000 stall Converter


Rear: 10 bolt 8.2" housing, Posi with 390 gears, 295/50/15 tires


Suspension: Full Hotchkis TVS 1" drop suspension (in the process of installing) with extreme sway bars and rear braces.


Power Goal- 400HP/450TQ


I decided to completely remove the rear end from my car to replace the bushings on it and learned quickly that the BFH is not for removing bushings on cast iron, doh! I can purchase a new 8.2" housing for only $50 and have my machinist swap everything over for $250. Just thinking now might be the time to address my high RPM issue on the highway (engine screaming at 60mph, probably 3700rpm, dont have a tach so not exactly sure but its insane). I do not want to change the transmission right now unless there is absolutely no way to get the rpms down to a tolerable level on the highway without sacrificing performance too much and be able to take the car over 100mph without blowing up!

My machinist is recommending 3.36:1 gears to get the best of both worlds without changing the TH400 and 355s if I want to go to a 2004r/7004r later. He says the 10 bolt/8.2" can be built to withstand my power goals if I DONT wheel hop. He also says, get the 336s to be happy on the highway and spend the money on ignition and fuel upgrades NOW to get to my power goal sooner. I never go to the track but would like good off the line accelleration, or at least 2nd/3rd gears to be awesome to catch up with other faster cars plus top speed of 100mph+ if possible especially if I were to spend $3000 on a 200r4 setup.

I am not sure which cam is in my engine, guy didnt give me a build sheet- its probably #1- 2725H but might be #2- 2728H.

Here is the link to Engles site, I also copy pasted both cam specs below

http://www.englecams.com/downloads/2010_engle_catalog.pdf

#1 Street & strip, brackets, jet boats. 10.0 to 11.0:1 compression IN .523” 282° .327” 236° 108° Powerband 2200-6200 RPM. 2725H EP-25/28HYD EX .555” 292° .327” 248°

#2 Drag racing, circle track modified engines. 10.5 to IN .555” 292° .347” 248° 108° 11.0:1 compression. Powerband 2500-6500 RPM. 2728H EP-28/29HYD EX .555” 300° .347” 256°

Options:
TH400- 308s,336s,355s
2004r/7004r-308s,336s,355s,390s,411s or 456s

Questions:
#1 Is my Converter stall too low for my setup in regards to power, fuel economy etc...?

#2 Does anyone have personal experience w/mating these gears with an overdrive transmission or a TH400 3speed? Will it be a total slug if I went 308s?

#3 What will happen to my acceleration in 1st and 2nd gears just driving around fast in-town and also vice versa, driving slow in-town trying to save fuel, will the trans shift later?

#4 Are 411s or 456s too much gear for my car? I was thinking put a huge gear in it, drive the car, save money and get the Overdrive Trans VERY VERY soon. Once the OD trans is in will I be in the same boat as far as high RPMs on the highway but now in 4th/OD gear? As mentioned before I would like to take the car to 100mph+ if possible, if so, is going with a 336 or 355 the highest gear I should run to acheive this in an OD transmission without blowing the engine?

 

Welcome to the site! Are you sure its an 8.2 rear end? The reason I ask is the factory rear end for a 1971 Cutlass should be the corporate 8.5 rear. If you have the 8.5 I'd go with 3.23 or 3.42 with the TH400. If you change to the overdrive then 3.73 or 3.91 might be better. I believe the 200R4 is a .67 overdrive. That would make a 3.91 rear end somewhere around a 2.70 in overdrive. This is all approximate as your tire height could noticeably change that. John

 

Thank you!

Yea, I measured it at a little less than 8.25". I guess the guy I bought the car from got rid of the original 8.5" housing, so Im stuck with this thing. I hear 12Bolt housings are $1200 and I dont really want to do that and pay for a new 8.5" posi unit+gears if my 8.2" will hold the power. I was just on the Richmond gear website, punched in 26.6" tires with 3.08 gears and 80MPH, i should have an RPM of 3100 which is ok, but with 336s I would be @ 4krpm, this is very high for me. I REALLY want the OD trans and keep the 391s which will give me 2700rpm at 80MPH, 100MPH @3400rpm or 120MPH at 4000RPM! that would be $$$weet!!

 

Correct me if Im wrong, if I get the 336s now and then upgrade to the OD trans later I MUST change the gears back to 390s in order to get the cars gearing correct for performance?

If this is true, I will probably HAVE to get the new 8.2" 10bolt housing, swap my 391 gears n posi over and do a trans swap, whats the easiest, cheapest and best performing trans, the 2004r or 700r4?

I hear the 2004r costs more, doesnt need an adapter plate, can use the TH400 crossmember, but the whole TV cable adjustment thing bothers me.

The 700r4 needs an adapter plate, is 1000 bux cheaper for one that supports 400HP and doesnt have such an overly sensitive Cable adustment procedure.

 

NEW DEVELOPMENTS!!!

3.90s @ 70MPH I AM CURRENTLY AT 3450RPM

3.36s @ 70MPH I would be at 2970RPM, a 480 RPM drop

3.08s @ 70MPH I would be at 2700RPM, thats a 750RPM drop!!

Im thinkin of keeping the TH400 and going with 3.08s and calling it a day, ANY THOUGHTS?!

 

That will work! It won't launch off the line as hard, but the torque of your engine will still push you back in the seat. If you can pick up another housing or complete rear end, the setup you have will be easier to sell complete. Also... I'd still like you to post pictures of the one you have right now, and get the casting numbers off the pumpkin and the stamp from the axle tube, pass side. I'm not an expert with rear ends but there's a couple guys here who are. They can help you identify it, figure out what a fair market price would be, and even provide the 3.08 posi you want. John

 

Thank you very much John, but I think I would like to hold on to the 390s just in case I end up getting a 2004r later on and want to upgrade since the 308s might cause my engine to choke on fuel in overdrive (extrmely low RPMS on the highway). Also as a side note the tubes did not have a code stamp, not sure as to why, either way its goin to the scrap yard.

I hate to go back and forth with this but the 336s seem like they are only 270 to 300 rpms higher on the highway, will the performance be a huge gain over the 308s??

 

I don't know your exact situation, but if you had room to store the rear end you have now that might save you money in the future. I haven't had it done but local shops here would charge at least a couple hundred dollars to change gears in a rear end. But I can find extra rear end housings easily for $50-75. So for me, it would be better to get another housing to install the posi carrier and other gears in. Or find a complete rear end with a posi and higher gears. Then at some future date you can just unbolt the complete rear end and swap the other one in if you want to.

Plus... do you have something rare? A 3.91 type O posi with 31 spline axles is worth twice as much as a more common 8.5 3.08 posi rear. Please take the time to figure out what you have before tossing parts in the scrap pile.

My 2 cents John

 

I have not spoken to my machinist today, he should have it all apart by tomorrow, I will definitely check to see how many splines the axles have and if anything is worth saving, duplicating or of any value, thx again John.

 

If you are building another rear,there's no real treason to take the 3:90 rear apart.You can keep it for later,when you get an overdrive.You could also get the correct 8.5" 10-bolt that should be in the car now.Where are you located?

 

Brooklyn NYC. I am having a hard time locating a used or new 8.2" BOP housing. What I really want is to just get my posi out of the damaged housing and swap it over to a new housing with some new Richmond 355s or 336s gears install it and call it a day. What do you have for me?

 

I need to hook you up with a guy in NJ that has a 64 Skylark with a 355 Chevy.He wants to put 4:11/posi guts into his existing 8.2" housing.
If that could all work-out,you could use the money towards a whole rebuilt rear.

 

Pm me his contact or just let me know his user name if hes on CO. Spoke to the machinist today, he said I have a 10bolt BOP housing and its going to be hard to find another 10 bolt BOP 10bolt 8.2" housing. He says the BOP 10bolt 8.2" housing is different than the chevy 10bolt 8.2" housing and I should start thinkin about a 12 bolt 8.875" housing with all new axles,posi, gears, wtf is this true? To add to this, I am completely confused about the gears I should use, I would really like 308s if its not going to make my car feel like a lead sled, boat aka slug on the street! I remember having stock 340s or 342s in my last cutlass with a 455/TH350 and they were still crappy on the highway when it comes to topping out RPMs, (getting frustrated) I hope I figure this out soon. In a perfect world I would get 355s or 373s and a 2004R and have it all, too bad I cant. So my question is, if I have to spend $1500 on a new rear end I would like to pick the gear that will be suitable for the TH400 that Im running now but still be good for a 2004R I hope to get later. I just hope whatever I choose for now (please be the 308s) dont suck, FML! PLEASE help!

 

No,you don't need a 12-bolt chevy.The 71-72 8.5" 10-bolt is all you will need for that car,and it is what came in that car originally.
After reading your first post,it looks like you broke one of the upper ears off your existing housing,so yes,that housing is junk.You now have a posi unit & gears.
I would still like to see a picture of the rear,to see if it really is an 8.2" or if it is an 8.5".Some 8.5's look just like the BOP 8.2's.

 

I measured the ring gear, its definitely an 8.2" ring gear and posi (POS, gonna toss it in the trash or sell on Ebay ). I guess the guy I bought the car from went the cheap route. So your saying the Olds 10bolt 8.5" is strong enough to handle some power and I shouldnt get the 12bolt chevy since its all getting swapped and i have to spend the money non? pics will be up very soon, i guess my phone is not sending for some reason

 

No offense,but you don't have enough motor to even begin to hurt the 8.5" 10-bolt.They can handle a bunch of power,and are less expensive to build than a 12-bolt Chevy because the cost of a 12-bolt chevy housing is steep,and that is what dictates the cost of the build. A good 8.5" 10-bolt core is about $100.00-$150.00,whereas a 12-bolt Chevy core is around $500.00,and you still have to rebuild both of them.

 

None taken. I actually found one, its a corporate 10 bolt 8.5 housing with 411 gears and a GM posi for 300BUX!! The Dood says its in great condition, says he had it in a 67 chevelle with a 468 but it was too wide and looked weird, duh! Only concern, will my huge 11 or 12" drum brakes fit on it and I think I need to inspect the case/axles/posi real well before I buy.

 

Heres a pic!http://i471.photobucket.com/albums/r...93429619_n.jpg

 

The rear pictured is an 8.2" 10-bolt BOP,with the original cone style posi unit.

 

Ok, cool, thanx!

 

Do you have a picture of the 8.5 that you found?

 

All of the ones I've been looking at are on CList. Do you have the app on your cell? Id love to send you a pic while I'm "on the scene" knowhatimean"?

 

You can send me pictures on my phone,but I can't send anything back.

 

Guy didn't contact me back yet. I found a different one: this ones a 10bolt 70-72 chevelle
Casting#3969277NF. Tube stamp AC204A. Guy says it has 273s and no posi, just wondering is this an 8.5 or anything strong? Does anyone know of a good web page or guide for future casting # referencing? Also at what RPMS does a 425 .030 over have the most torque and power? I think I might go with gear placement based on power level at rpm with the TH400 behind it...

 

That Chevelle rear is an 8.2" 10-bolt,not an 8.5". Do not pursue it.