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Old 02-15-2006, 12:23 PM
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Will a 700R4 withstand BBC 500+ lb-ft of Torque?

Hey all, I will be inheriting a 1971 Camaro Z-28 with no tranny or engine in it.

I'm going to build a 496 BBC stroker for it and I wanted to use a 700R4 transmission because I like them a lot.

I know the main thing with big blocks is to bolt them to a TH-400 tranny, but I want a 700R4.

The car has a 3.73 rear end with (haven't confirmed yet) positraction.

Is this plausible? or will the 700R4 just crumple under the massive amount of torque my 496 will be putting out.

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Old 02-15-2006, 01:42 PM
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Trans

Need a little more info,

Is this going to be a drag race car only???

Is it never going to be raced???

Slicks?? What size???

Are you willing to spend any amount of money on the 700????

Keith
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Old 02-15-2006, 03:07 PM
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Malibu73,

I am doing the same thing, and, it appears there are Transmission Builders out there that say they build them to 575 h.p., 600# Torque-try Phoenix Transmissions. It seems like 575-600 h.p. is the top end-I am considering a 4L80E (Phoenix builds them up to 1000 h.p.). With all of the Torque of a 496, I don't think the lower 1st gear will be needed-

www.phoenixtrans.com
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Old 02-15-2006, 03:32 PM
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Thanks for that link 35window.

The car will be a street machine, with very occasional track use.

Mainly to be driven on street/highway and romped on regularly

I'm going to build a 496 BBC but I'm not exactly sure of the output numbers yet.

I would like something like 500HP/500TQ, but I want more torque than horsepower. So maybe 450HP and 550-575lb-ft Torque.


Like a I said earlier, the common thing to do would be to get a TH-400 and bolt it to the engine, but with the 3.73 gears I would kind of like the 4th gear of the 700R4.
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Old 02-16-2006, 12:52 AM
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I really want that 700R4 because I've been doing some calculating and if I had a TH-400 3spd, cruising at 60MPH with a 24" wheel+tire would be 3150RPMs! Now if I had the 700R4, that 4th gear overdrive with the same tire size would drop it down to 2200RPMs @ 60MPH, a much more economical and more fun cruising RPM (not that a 496 BBC would be economical anyway). Plus at 2200 RPMs the BBC would have MORE than enough torque to push the car along easily.

So do you see what I'm getting at? That's why I'd like to build a 700R4 to put behind that engine, I just need to know if it'll stand up to it.
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Old 02-16-2006, 07:18 AM
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24" Tire? Are you sure about that?
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Old 02-16-2006, 11:44 AM
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Try thinking of it a different way... The car is relatively light, and the engine makes gobs of torque, and you have a 3.73 rear. There is no way you need 3.73s. You'll probably actually give up acceleration with a first gear that low.

Do the TH400. You have lots of torque, the 700's first gear is a basement-low 3.06, and you're using tiny tires. That's granny gear territory with the 700. There is no way you'll get traction, you'll be out of first gear by 25 mph, and your accleration will be terrible. The TH400 has a much wiser gear spread, takes tons more torque, and then put some 3.42 or 3.23s in the rear. Heck, you could go with 2.73s and all you do is roast those tiny tires.

Its common to think that OD is the way to get better cruise RPMs, which is true, but ONLY if you need a low final drive to match the car's acceleration properties. When you have a light car with lots of torque, you don't need it. You have the ability to choose a rear ratio that does both; provides optimum leverage for acceleration, and proper cruise RPM.

I have a 66 Bonneville with a Caddy 500. It has a final drive of 2.95 and all it does is melt the 255 26" rubber through a TH400. Cruise RPMs are something like 1900. If I had chosen the 3.42s with an OD, I would have basically created an extra gear lower than my current first gear and that would really have messed me up. It would be useless.

More is not better. Right is better. The 700 is a very wide ratio 4-speed that really has no place in a light car with that much torque. The 400 is a close ratio 3-speed that will be perfect.
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Old 02-16-2006, 12:49 PM
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Well, the car is going to get new wheels and tires, I just have no idea what they're going to be yet. I want 15 inch wheels with wide tires in the back and smaller up front. Or, wide tires all around. I'm open to suggestions for this.

The current tires on my chevelle are 215/70R15, I'd like my camaro tires to be like 235-255.

The main reason I was thinking the 700R4 was for the cruising gear, 3rd on a TH-400 with the 3.73 would be something like 3000RPM's @ 60. I don't want to change out the rear end, unless I can find another one easily, but changing the rear end wasn't even in my plans.


What I'm hearing from you is that the TH-400 would have a better wider gear range that would go better with the amount of torque Iím going to have, which makes sense. I know for a fact that the 700R4 has a closer range of gearing;

1st: 3.06, 2nd: 1.62, 3rd: 1.00, 4th: .70

The TH-400 gear ratios are 1st: 2.48, 2nd: 1.48, 3rd: 1.00

First and second are significantly lower on the TH-400 than the 700R4, but to get those lower ratios I sacrifice that 4th gear.


Why donít they make a wide ratio 700R4?
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Old 02-16-2006, 08:29 PM
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You have it backwards. Lower numbers mean a higher gear. The 400 is the closer ratio box. Notice the spread between numerical ratios. The 700 has a really low first gear at 3.06, then it jumps an incredible spread up to second at 1.62. That will make an RPM drop of 2800 RPMs when you shift up to second. Talk about falling out of peak power range. Not one of GMs wiser moves in my opinion.

If this were a small block in a heavy car, then yes... 3.73 with an OD. You need that low gearing to make up for the fact that the engine doesn't make as much torque. You also need it to get the heavy car moving. The math works out like this. If you go with your current plan, in first gear you'll be putting 5700 lb-ft of torque to the rear wheels of a light car. I put 3110 lb-ft to the rear wheels of a very heavy car with 255mm rubber and there is no such thing as traction.

Even if you put 3.08s in that car, you're still putting 3900 lb-ft of torque to the rear wheels in first with radials on a light car. You'll be wasting all that torque as tire smoke.

Set it up right. If you're unwilling to change the 3.73s (no offense intended) then you've chosen the path of least resistance and ultimate performance is not your goal. which is fine, I was just offering some advice on how I personally would set it up... But its not my car

Whatever you do... enjoy it. Sounds like a killer ride.
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Old 02-17-2006, 04:53 PM
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Back to your basic question, a stock 700R4 will not stand the HP and torque you are planning. Go with the the reputable builder specs that they warranty and you should be good.

Trees
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Old 02-18-2006, 03:52 PM
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Quote:
Originally Posted by curtis73
You have it backwards. Lower numbers mean a higher gear. The 400 is the closer ratio box. Notice the spread between numerical ratios. The 700 has a really low first gear at 3.06, then it jumps an incredible spread up to second at 1.62. That will make an RPM drop of 2800 RPMs when you shift up to second. Talk about falling out of peak power range. Not one of GMs wiser moves in my opinion.

If this were a small block in a heavy car, then yes... 3.73 with an OD. You need that low gearing to make up for the fact that the engine doesn't make as much torque. You also need it to get the heavy car moving. The math works out like this. If you go with your current plan, in first gear you'll be putting 5700 lb-ft of torque to the rear wheels of a light car. I put 3110 lb-ft to the rear wheels of a very heavy car with 255mm rubber and there is no such thing as traction.

Even if you put 3.08s in that car, you're still putting 3900 lb-ft of torque to the rear wheels in first with radials on a light car. You'll be wasting all that torque as tire smoke.

Set it up right. If you're unwilling to change the 3.73s (no offense intended) then you've chosen the path of least resistance and ultimate performance is not your goal. which is fine, I was just offering some advice on how I personally would set it up... But its not my car

Whatever you do... enjoy it. Sounds like a killer ride.
3.73 I've heard are suppose to be a good balance between acceleration/topspeed. If the gears were any higher, I would change them out.

However, I want to keep the 3.73 rear end. Maybe I just will end up having to use the TH-400. It would be the easiest, I could keep the stock floor shifter in there too
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Old 02-18-2006, 07:10 PM
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Quote:
Originally Posted by Malibu73
3.73 I've heard are suppose to be a good balance between acceleration/topspeed. If the gears were any higher, I would change them out.

However, I want to keep the 3.73 rear end. Maybe I just will end up having to use the TH-400. It would be the easiest, I could keep the stock floor shifter in there too
The best gears are the ones that work with your tranny ratios, the weight of the car, and where the torque peaks in the engine. Its entirely your choice, but I'm just trying to give you the whole picture. Saying 3.73s are the best balance is like saying that a small block is the best engine for everyone's car.

An example... My car currently has a 4L60E (same ratios as 700r4). I'm swapping it out for a T56 six speed manual. I'm going from the stock rear ratio of 3.08 down to 4.10s. That's a 34% change, but because of the gearing in the T56, my cruise RPMs will be LOWER after the swap. If I had kept the stock 3.08s, I would have been unable to use 6th at all, and 5th only above about 70 mph. My first gear would be like starting in 2nd. You have to take ALL of it into consideration when you plan it. There is no "best" gearing.

Just consider that simply a different tranny in my case is allowing me to change from 3.08s to 4.10s and drop my cruise RPM in the process. Many guys who are doing the same swap as me are going from 3.08s to 4.56 and it only makes a 100-RPM rise at cruise.

I'll leave you alone now I just wanted to make sure you have all the info. I truly think your unwillingness to change out the 3.73s is a little close-minded and it may lead to regrets later, but its your car. No arguments intended, just wanted to lay it out there
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Old 02-19-2006, 08:24 PM
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Quote:
Originally Posted by curtis73
The best gears are the ones that work with your tranny ratios, the weight of the car, and where the torque peaks in the engine. Its entirely your choice, but I'm just trying to give you the whole picture. Saying 3.73s are the best balance is like saying that a small block is the best engine for everyone's car.

An example... My car currently has a 4L60E (same ratios as 700r4). I'm swapping it out for a T56 six speed manual. I'm going from the stock rear ratio of 3.08 down to 4.10s. That's a 34% change, but because of the gearing in the T56, my cruise RPMs will be LOWER after the swap. If I had kept the stock 3.08s, I would have been unable to use 6th at all, and 5th only above about 70 mph. My first gear would be like starting in 2nd. You have to take ALL of it into consideration when you plan it. There is no "best" gearing.

Just consider that simply a different tranny in my case is allowing me to change from 3.08s to 4.10s and drop my cruise RPM in the process. Many guys who are doing the same swap as me are going from 3.08s to 4.56 and it only makes a 100-RPM rise at cruise.

I'll leave you alone now I just wanted to make sure you have all the info. I truly think your unwillingness to change out the 3.73s is a little close-minded and it may lead to regrets later, but its your car. No arguments intended, just wanted to lay it out there
Thank you for doing that. Maybe I will end up switching gear ratios to 3.08's or something else. It's not really a problem to do it, I just wasn't planning on it. Since I've talked here though, putting that 700R4 up to those 3.73's would give me an incredibly short first gear.

Maybe I'll do a TH-400 with 3.08's, that should give enough gear for the 496 to grab hold of

Or should I go with a lower gear + the 700R4?

Decisions decisions........
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Old 02-19-2006, 09:55 PM
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Well I suppose it all comes down to what you want to do with the car. I think it'd be a mistake to go to a 3.08 gear. The 3.73's should work well. With a 700r4 the first gear is quite low, but I'm not convinced that it's as detrimental as some claim. The real problem is there's quite a jump from 1st to 2nd. With a torquey big block, it'll probably cover the span well enough for a street/strip car. I've used 3.73 and 4.10 with a 700r4 and they've both worked well. Traction can be a potential issue in 1st, but a set of slicks and a good track will keep it hooked until you get really fast. On the street it'll spin the tires, but that'll happen anyway because the street doesn't have near the traction as a good track.

If this is going to be a mostly street car, I think you'd be happy with the performance of the 400 or 700. If you're going to be doing a lot of driving on the freeway the 700 might be worth it. BTW you won't be running 24" tires. My 265/50 bfg's are around 26". On that car you'll probably have 26-28" tires.

To get back to your original question, a 700r4 can take that power but it'll have to be built by somebody who specializes in performance 700's. It won't be cheap. If you want to do it right it's going to cost money. Half the price of building a powerful engine is putting together complimentar components that'll handle the power. If you want to play you have to pay. Another option would be a 400 with a gear vendors overdrive. In the long run it might be cheaper and it would certainly handle more power than a 700. Do a search for gear vendors.
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Old 02-20-2006, 10:08 PM
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Originally Posted by dh79
Well I suppose it all comes down to what you want to do with the car. I think it'd be a mistake to go to a 3.08 gear. The 3.73's should work well. With a 700r4 the first gear is quite low, but I'm not convinced that it's as detrimental as some claim. The real problem is there's quite a jump from 1st to 2nd. With a torquey big block, it'll probably cover the span well enough for a street/strip car. I've used 3.73 and 4.10 with a 700r4 and they've both worked well. Traction can be a potential issue in 1st, but a set of slicks and a good track will keep it hooked until you get really fast. On the street it'll spin the tires, but that'll happen anyway because the street doesn't have near the traction as a good track.

If this is going to be a mostly street car, I think you'd be happy with the performance of the 400 or 700. If you're going to be doing a lot of driving on the freeway the 700 might be worth it. BTW you won't be running 24" tires. My 265/50 bfg's are around 26". On that car you'll probably have 26-28" tires.

To get back to your original question, a 700r4 can take that power but it'll have to be built by somebody who specializes in performance 700's. It won't be cheap. If you want to do it right it's going to cost money. Half the price of building a powerful engine is putting together complimentar components that'll handle the power. If you want to play you have to pay. Another option would be a 400 with a gear vendors overdrive. In the long run it might be cheaper and it would certainly handle more power than a 700. Do a search for gear vendors.
Thank you for your point of view. I have seen the gearvendors before 9been to their website etc...). I'll have to investigate those two possibilities, but the last time I checked, a gearvendors gear splitter ran over $2200, which is a lot more than I care to spend on a tranny.

However, I also need to check into the cost of building up a 700R4 to handle that much torque, the costs might be similar.

I will probably be doing more highway driving, as well as around town driving too. That's the main reason I liked the idea of having the 700R4, was that 4th gear for the highway.

~~edit~~ I was just doing some calculations and with a 26" tire, and 3.73's, at 5500RPM's I'd only be going 114MPH.....Yeah....I think I'm gonna need that extra gear, or at least a higher rear end. I want to be able to hit 125-130...

Last edited by Malibu73; 02-20-2006 at 11:27 PM.
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