Auto - v - manual
Thread Starter
Drifting
Joined: Sep 2004
Posts: 1,307
Likes: 1
From: Milford Haven Pembrokeshire
Auto - v - manual
Couple of questions.......
Anyone know the typical losses ( bhp ) through a th350 and th400 - unmodified....
Same question for a 4 speed manual....
Also, what sort of power will each each take ( unmodified ) before it all lets go.
Same question for a stock rearend - is a 383 stroker the first step to the dark side ??
Anyone know the typical losses ( bhp ) through a th350 and th400 - unmodified....
Same question for a 4 speed manual....
Also, what sort of power will each each take ( unmodified ) before it all lets go.
Same question for a stock rearend - is a 383 stroker the first step to the dark side ??
Burning Brakes
Joined: Oct 2004
Posts: 1,132
Likes: 0
ttt. I'm interested in this also
How much can the rear end take on an automatic 71 - given that it can hook up at any HP.
I'm looking to get some drag radials or slicks and some fast burn heads and am wondering if I need to upgrade anything else.
How much can the rear end take on an automatic 71 - given that it can hook up at any HP.
I'm looking to get some drag radials or slicks and some fast burn heads and am wondering if I need to upgrade anything else.
Last edited by majic1984; Oct 21, 2005 at 12:58 PM.
Racer
Joined: Aug 2005
Posts: 456
Likes: 0
From: Forty Fort PA
Just looking at what chevy did, the standard rear was used with the L-88 and LS6 engines. These produced well over 400 HP (rumor has it that the L-88 was much higher). These engines were offered with the Muncie M-22 4-speed. This transmission has a different helix angle on the gears to reduce the side loads on the internal shafting. The result is a box capable of withstanding higher torques.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
HP is not what breaks the parts. It is traction. If you are running street tires you can run lots of hp the tires are just going to spin. If you run drag radials or slicks the stock components will let go. I have seen 400 HP blow up a rear but they were running slicks. I always use 500 HP on street tires as a safe bet providing everything is in good shape. Past that you are asking for trouble. If you are running slicks go buy a bucket to carry your parts home in. Toms differential has heavy duty parts for the rear if you are going racing.
Drifting
Joined: Nov 2004
Posts: 1,971
Likes: 7
From: Longwood Florida
YES....
SLICKS WILL KILL YOUR CAR WITH LOTS OF HORSEPOWER AND A MANUAL TRANNY.
They say that manual tranny uses least amount of power.
Then a Power Glide..
then a TH350 or 700R or 200R
Then a TH400 takes the most power but is the strongest factory tranny.
People that have moved from one tranny to the other may see just a few 10ths difference is ET.
SLICKS WILL KILL YOUR CAR WITH LOTS OF HORSEPOWER AND A MANUAL TRANNY.
They say that manual tranny uses least amount of power.
Then a Power Glide..
then a TH350 or 700R or 200R
Then a TH400 takes the most power but is the strongest factory tranny.
People that have moved from one tranny to the other may see just a few 10ths difference is ET.
Melting Slicks
Joined: Sep 2004
Posts: 2,412
Likes: 3
I think the rule of thumb is 15% loss for a manual and 20% for an automatic.
And manuals are always faster until you start to reach ridiculous HP levels. Then an automatic will get you the lowest time despite the extra loss.
But don't let this be the determining factor, take in to consideration fun factor and the possibility of stop and go driving. Stiff clutches don't feel so bad until you hit a jam on the freeway.
But for me, its gotta be fun factor. If not for fun, then what else?
And manuals are always faster until you start to reach ridiculous HP levels. Then an automatic will get you the lowest time despite the extra loss.
But don't let this be the determining factor, take in to consideration fun factor and the possibility of stop and go driving. Stiff clutches don't feel so bad until you hit a jam on the freeway.
But for me, its gotta be fun factor. If not for fun, then what else?
Tech Contributor
Joined: Aug 1999
Posts: 15,166
Likes: 3,968
From: Connecticut, USA
You can beef up the rear end if you have it out but as the others say if you're going to use slicks all bets are off.
Tom's 12 bolt is nice but is it what you're really going to need? I've built some good HD diff's for street tire cars 400-500 hp but it all comes down to use. Push it hard enough, long enough, and something will break.
I snapped a NAPA1/2 shaft u-joint in half shifting at 3,000 rpm, hardly pushing the car and the jiont only had 18k miles on it.
Gary
Tom's 12 bolt is nice but is it what you're really going to need? I've built some good HD diff's for street tire cars 400-500 hp but it all comes down to use. Push it hard enough, long enough, and something will break.
I snapped a NAPA1/2 shaft u-joint in half shifting at 3,000 rpm, hardly pushing the car and the jiont only had 18k miles on it.
Gary
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Thread Starter
Drifting
Joined: Sep 2004
Posts: 1,307
Likes: 1
From: Milford Haven Pembrokeshire
So, are we saying the loss is a percentage rather than a fixed amount ??
A 350 will lose you 20 bhp hooked up to a 100 bhp engine, but the same box will lose you 100 bhp hooked behind a 500 bhp engine ??
I thought the loss would be a fixed amount due to internal frictions, etc,
Getting confused now -
need an expert to explain clearly.........
A 350 will lose you 20 bhp hooked up to a 100 bhp engine, but the same box will lose you 100 bhp hooked behind a 500 bhp engine ??
I thought the loss would be a fixed amount due to internal frictions, etc,
Getting confused now -
need an expert to explain clearly.........
Safety Car
Joined: Oct 2004
Posts: 3,924
Likes: 735
From: Youngstown Ohio
Originally Posted by hensen1954
So, are we saying the loss is a percentage rather than a fixed amount ??
A 350 will lose you 20 bhp hooked up to a 100 bhp engine, but the same box will lose you 100 bhp hooked behind a 500 bhp engine ??
I thought the loss would be a fixed amount due to internal frictions, etc,
Getting confused now -
need an expert to explain clearly.........
A 350 will lose you 20 bhp hooked up to a 100 bhp engine, but the same box will lose you 100 bhp hooked behind a 500 bhp engine ??
I thought the loss would be a fixed amount due to internal frictions, etc,
Getting confused now -
need an expert to explain clearly.........
Drifting
Joined: Nov 2001
Posts: 1,469
Likes: 6
From: 68 427 4.11s Roadster
I asked this same question and the same ? about the losses per hp.
I came to the conclusion or thought method that its not the same friction at all times. Friction would increase with an increase of pressure.
Like the friction on the gears. More torque is more pressure. Since all gears slide I figure even if the concept is wrong it makes it understandable.
Roller bearings might produce more heat, but oil wedge bearings definately do and so would gears. Heat is power.
I came to the conclusion or thought method that its not the same friction at all times. Friction would increase with an increase of pressure.
Like the friction on the gears. More torque is more pressure. Since all gears slide I figure even if the concept is wrong it makes it understandable.
Roller bearings might produce more heat, but oil wedge bearings definately do and so would gears. Heat is power.