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Old 01-11-2006, 01:53 AM
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7 hours, 33 phone calls, &30 pages of Threads later... Rearend? Tranny? Need Guidance

Hi all, newbie to the site and to restoring a muscle car so I got many questions I was hoping you could help me answer. I guess to give you guys a better understanding I'll explain my project car. I currently own a 68 Chevelle looking to overhaul entirely and be there to WORK on EVERY STEP of it. The body is good, interior is fairly decent, but right now i'm looking to beef up the drive train and rearend. It has a 350 SB in it with a 350T I believe and a 12 Bolt Open with .278 gears. I'm building the car intended as more of a street rod rather than taking it to the strip, however I do want to be able to stomp out the local rice burners and show them the best era of cars built. I'm prolly going to keep a small block in their for economic purposes however i do want some fire under my tires so what route should i take?

First, i want to know if i'm wrong for starting with the rearend when i am not entirely sure what size motor i'll be putting in... (most likely gonna stick with a 350 and beef it up, but considering a 383 stroker or 400 SB) So if you guys have suggestions, please do so. Going off my older friend/mechanic's advice, we were gonna put a posi rearend with .373 gears in it. Now, would it be insane to swap some guy even up my 12 bolt .278 one-legger for his 10 bolt posi with .373 gears? I'm sure u guys will be all over for me this question as I've done a lot of research and found that the 12 bolt is a lot stronger and worth a lot more in the long run. I am on a budget $8000 - 10,000 to redo the drivetrain and rear so I'm willing to spend the extra buck but not go overboard or spend lavishly. I found a link of some guy in NJ selling 12 bolt posi carrier for $700 or should I get one of those Eaton posi kits off eBay or elsewhere? Anyone know the prices on those or a site that sells them cheaper? I read the Auburns suck and Powertraxx are noisy as hell.

Moving on, what kind of manual tranny do you recommend? I currently have a 350T automatic with a shift kit looking to swap it back to its orginal 4-speed. [Could u rebuild this to be a 4-speed?] I read/heard the M20's are not as good as the M21's (bear in mind I want higher numerical gears) and I think the M22 might be out of my range and not neccessary for my purpose. It seems Saginaw's are good for the inexpensity of them but not as good as a Borg Warner which I have been offered one for $400-500 that will need rebuilt I believe. Is this a good deal? I found an older local who does a good job rebuilding trannies but isn't that expensive.

A few oddball questions - what HP and torque range can a 12 bolt posi .373 rear handle? (for future reference when it comes time to rebuild a small block). Also, does anyone know any of any excellent hot rod shops that exists within the state of Pennsylvania? Oh, and before you guys ask about the tire size, I don't know off hand and it's dark out but I'm willing to change the tire size according to whatever changes are made to my car. Lastly, what is the difference between an open and closed rear? I think that's all guys. So Deuce, Fulco, all you other experts lemme hear it from you guys. Thanks a lot and looking forward to hear suggestions from everyone!!!

- Justin

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Old 01-11-2006, 06:11 AM
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Hey 68; Since u asked this is what I ran in my 66 chevy short fleet pick-up and it was rice proof and bullet proof. 350/425hp,T350 with a stage three shift kit and a B&M slap shifter,3:73 posi gears in a 12 bolt. It was manual shift and when u shifted it from first to second it would wack your passengers head of the rear window. Personnaly I'd stick with what you got and just make it better. You should be able to stay within your $ window no problem. Good luck. Cheers!!!
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Old 01-11-2006, 07:11 AM
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When you say "stick with what i got", are you referring to my rearend or automatic with a shift kit? I like the idea of a 350/425hp setup that you have, I wouldn't mind getting more of a detailed description of your small block. Also was your 12 bolt a posi? I think i'm gonna hang onto this 12 bolt and convert it to a posi b/c they seem hard to get and what everyone wants. As far as the tranny, i think i wanna swap it to a 4 speed. Any suggestions? I was thinking of a Super T10 b/c it's aluminum and has a closer gear ratio... M22 Rock Crusher are a lil outta my range. Thanks a lot bud. I really appreciate your response as well as others. If it wasn't for you older guys, us younger guys wouldn't keep this era of cars alive... hope to hear back soon... thx, later.
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Old 01-11-2006, 07:11 AM
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as for 12 bolt vs 10 bolt in your application the 10 bolt will be plenty strong for street cruising with a mild 350. The Posi and the 373 gears are very desireable so I would recomend the swap with your buddy. No cost and you will get a very noticeable improvement in low end acceleration.

As for the transmission. Changing back to the stock 4 speed that came in the car will be plenty strong for your application but expensive. I would recomend staying with the turbo 350 for cost reasons. When you build the engine be sure to stay away from high duration cam shafts. Tell the cam supplier what the use of your vehicle is the gear ratio and the transmission type and they will hook you up with the right one.

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Old 01-11-2006, 07:30 AM
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Without getting too detailed if I were in your shoes I would build a mild 383, 200-4R or 700R4 OD and get a posi unit and 3.73's for the 12 Bolt. Personally unless you are towing or running a BIG big block I prefer the 200-4R, some people prefer the 700R4, either one is a good choice for your application. 4 speeds are fun but you WILL break stuff, been there done that but if you must have one consider a Richmond 5 speed instead, last time I checked they weren't that much more than a fully refurbished Muncie or B-W and you get much better gear multiplication and can gear your car for lower highway RPM to save some gas. Don't go hog wild on intake, heads and cam, build it for torque below 5,500. Take a look at the Lunati VooDoo cams, heads with around 180-185cc intake runners and an Edelbrock Performer. Hit the right combination and you'll have a car you can drive everyday if need be on whatever gas is available and that will use less of it than most new SUV's plus will easily run in the 13's and I would say well within your budget.
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Old 01-11-2006, 07:56 AM
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If you can get the 3.73/posi....Go for it. As said, if you have that gear, an overdrive auto trans is the way to go. A 4 speed on the street can be a pain.......clutch problems, etc.... The auto is much less hassle.
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Old 01-11-2006, 08:10 AM
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Keep it Simple

The 10 bolt posi is a good rear for mild apps. Make sure it will mount up without modification. If it does not I would add a posi unit to your rear. The turbo 350 is a good strong trans for the budget. I like the edelbrock head and intake combo on a rebuilt short block, nice power and reliable.
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Old 01-11-2006, 08:57 AM
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Dude if your building a street driver that runs on pump gas then keep the rearend and tranny that you have. They are more than enough.

Service them or whatever they need. Change gears etc.

If you go removing the rear end etc, you might end up breaking more than you fix during the R&R.

Have fun. Happy Hot Rodding
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Old 01-11-2006, 05:28 PM
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Hey 68; When I said stick with what u got I meant both rear end and the T350 and yes the rear end was posi. I'm still a believer in the T350 just for the sake it is bullet proof. I had a real good friend who was in quality control for GM in the tranny plant in Windsor. When a tranny came back after inspection it was checked and sent back, if it came back a second time he would make sure it never came back. He said it was the hardest tranny of all to scatter. For racin' them ricers the stage three shift kit will blow any four speed out of the water. It'll shift gears before the guy with the 4 speed can get to the neutral position let alone in the next gear. I raced more ricers and 5.0's with that ole truck and she never let me down. Just remember though, you can have all kinds of pwr but you got to get it from the front to the pavement. That's where it counts. Just one last thing. That setup has now run for over six years and its been run harder then any other rod I know of. My ex-brother in law has the running gear in a '56 chevy now for last three years. You will get alot of great ideas on here. There's a great bunch of knowledgeable guys on here that will jump in and help you any way they can, they've helped me alot. Good luck. Cheers!!!
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Old 01-11-2006, 05:36 PM
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7 hours, 33 phone calls, &30 pages of Threads later... Rearend? Tranny? Need Guidance

Hi Justin:

got your request for comments on your project.

You have received some great advise so far. One point I might add is that, since this is your first project, you might want to consider saleability - with driveabilty. Don't go crazy spending a small fortune with the expectation of only 30% return of funds invested.

A decent motor, positraction, and an overdrive automatic tranny can get you there. Then, when you are ready, move on to your next project using the lessons learned from this one.

Animal
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Old 01-11-2006, 06:30 PM
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I also agree with most of the above posts. I would keep the TH350 and the rear end you have, both are plenty strong enough for what you are building and you will apreciate the higher 2.73 gears if you do much highway driving. You can fairly cheaply add a shift kit to the TH350. This is of course assuming it is in good condition now. Changing over to a standard from an automatic is not a small task. The days of everyone having to have a 4 speed with a Hurst shifter have passed. yes they are cool but shifting gets old afer a while.
Good luck with you project
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Old 01-12-2006, 12:31 AM
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Start with one question i have is the 10- bolt. Is it a 8.5" 10 bolt or the smaller version. if it is the 8.5" it will handle the power. we got people over at second gen running 9's with a 10 bolt 8.5" but he has the usual mods done, like better axles, c-clip eliminators. but for a car running 12's or higher it will be fine stock.

the 12 bolt is the better rearend of the two due to the bigger ring, but not very much. also the pinion bearing is better. need to make sure that the 12 bolt is in good shape, if it is i would keep it and swap the gears and such in it. but the cost of someone setting gears for ya can get high.

i rebuilt the 10 bolt 8.5" i got and it has 4.10 with posi in it. The reason behind this is i had it already like that, just needed to freshen it up. to stay in budget.

As for tranny, I perfer th400, due to it can handle high torque all day long. If you sent the th350 out to be beefed up it can handle any power you can get out of a N/A motor. meaning no blower, no turbo, little nitrious. The only draw back behind the th400 is you lose afew HP due to the rotating weight. it is heavier(in the right spots) then the th350 which makes it stronger. If you want to bracket race then auto will be better due to your shifting would stay the same and you won't break your time.
But if you want play toy fun then standard might be your way to go, which is what i want to do myself if i come across the complete setup for a 79 camaro in the area for a decent price. But as mention this can cause headaches too, you have to worry about the shifter linkage and the clutch setup and all of the stuff that is in the way to let the linkage work properly.
But for budget wise, i would send the tranny out and get it beefed up alittle. around here if you go out with it, they usually charge $600-$800.

then the motor, there is so many ways to go, that this makes it fun! you ain't got to follow someones else's buildup but it would be a good starting point. If you have the tools and know how on building a motor, then rebuild a 350 and add all of the normal goodies. for budget heads go vortec, but when you get to the intake you will have to get vortec specific intake. Also rocker arms have to be self-align, unless you put in guide plates and screw-in studs.
If you don't have the know how it might be cheaper to buy a long block and just put the normal goodies on it. Check out www.sdpc2000.com for ideas on crates motor and such. it might be cheaper down the road for ya.

If ya got anymore question let us know and i am sure someone will chime in!
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Old 01-12-2006, 12:32 AM
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Oh about shifting getting old, naw it just means everyone else is getting old!! lol

I perfer shifting my own gears.
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Old 01-12-2006, 03:21 AM
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You sound like your kinda set on a 4 speed. If thats the case you could find a junk M20 and M21erize it with new gears and parts. I'd also keep the 12 bolt and go through it with your upgrades. You can get the tools and learn how to do this and your own tranny work. Once you know how, your friends and their friends will keep you knee deep in rears and trannys. Narrowing housings also brings in money. You could actually rebuild a lot of the Chevelle with money made off of these services.
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Old 01-12-2006, 07:51 AM
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Quote:
Originally Posted by madison069
Oh about shifting getting old, naw it just means everyone else is getting old!! lol

.
Aint that the truth
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