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Transmission & Driveline Transmissions and Differentials

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  #1  
Old Nov 24th, 12, 11:30 AM
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67Rally 67Rally is offline
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Brent
 
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Default Transmission questions...

I'm thinking about having my engine bored and stroked this winter to breath a little life into it, and if so, I'm looking at roughly 450hp/450tq. I'm fairly certain my 4 spd Saginaw is not going to be happy with that power. And while I'd love to upgrade to a TKO 500/600 or even a T56, it's probably not in the cards if I don't want to cut corners on the engine build. This is going into a street car than I like to beat the snot out of, it will likely never see a drag strip, although an occasional auto-x is not out of the question.

I have no idea what the current Saginaw has for gearing, but first gear feels like a granny gear to me, and I need something different.

1) What is an ideal final drive ratio for my first gear? I have a 12 bolt posi with 3.31's, and a 26.7" tire.

2) Is there any way to tell what gears my current Saginaw has without pulling it out?

3) If I leave the Saginaw in there and just drive it hard till it dies, do I risk doing damage to any other components?

4) Will an M20 (2.52, 1.88, 1.46, 1.00) work well with my current 3.31's? I think the M21 (2.20, 1.64, 1.28, 1.00) would be better suited to a higher rear end gear?

5) If I could swing the extra dough, would I be better off with a TKO500 (3.27, 1.98, 1.34, 1.00, .68) or with a TKO 600 (2.87, 1.89, 1.28, 1.00, .82 or .64)?

Thanks for any insight.
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  #2  
Old Nov 24th, 12, 01:24 PM
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Kevin
 
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Default Re: Transmission questions...

Brent,
I can't imagine what gears in the trans you could have that makes a car with 3:31 rear feel like a "Granny Gear" in first! Post some numbers of the transmission so we can check what gears it may have. I ran a Super T-10 with
3.42 =1st 2.28=2nd 1.46= 3rd 1.00= 4th and ran 4:10 12 bolt posi and BFG 255-60-15's on the rear. I would go 15 feet and need to shift to second but if I got on it..its was a rocket out of the hole This is why I say that the trans you have is geared too high (truck trans) or your rear isn't a 3:31. I would wait to get a TKO later on if I were you. Go with the .68 overdrive TKO ! PM me as I have some info for you.

Kev
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  #3  
Old Nov 24th, 12, 01:38 PM
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Brent
 
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Default Re: Transmission questions...

Thanks Kevin. The rear is definitely a 3.31. I had it apart earlier this year.

I'll post some pics of the tranny tonight or tomorrow.
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  #4  
Old Nov 24th, 12, 06:31 PM
Melrose RS Melrose RS is online now
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Default

Brent, worst case that you could possibly have in terms of a granny gear would be a Saginaw like mine with a 3.50 low. That would yield you an 11.5:1 overall first gear with your 3.31's. 9.55:1 in my car with 2.73's.

A combo many people like is the m20 with a 3.73 rear. That works out to a 9.3:1 overall first. Pretty good for take off. Now if you put the m20 with the 3.31's you get 8.3:1. So-so in my opinion but with enough torque should work good. I'd shoot for between 9.3-10:1 for a fun first gear.

If you took the tko500 with 3.27 low you'd have 10.8:1 first. With tko600 and 3.31's you'd have 9.5:1 first gear and 2.11 final with the .64 O/D or 2.71 with the .82 O/D.

Knowing how fast we drive on the highway around here, i'd probably go with the deeper o/d if the engine is happy down around 1,900-2000rpm range. With the .82 o/d you'll be around 2,400 - 2,500 at 70 mph.



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'67 rs - ordered new by my Grandfather
327 L30, K-K, Deluxe int, tach & gauges, 12 bolt posi, 4 speed.
the Melrose rs - L30 327/275hp

Last edited by Melrose RS; Nov 24th, 12 at 07:30 PM.
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  #5  
Old Nov 25th, 12, 04:54 AM
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Brent
 
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Default Re: Transmission questions...

Here are a couple of shots of the transmission. Sorry for the quality:


It looks like 2048 and 3925656?:




It looks like 2042N and K2D25 or K2B25?:

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  #6  
Old Nov 25th, 12, 06:03 AM
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Kevin
 
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Default Re: Transmission questions...

Brent,
The 3925656 is as follows;

Saginaw M20 68-69 3925656 2.54 1.80 1.44 1.00 V8 engine


What if any rings are on the input shaft? The 2:54 first is like my ST-10 2:28 second!

Kev
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  #7  
Old Nov 25th, 12, 06:12 AM
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Brent
 
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Default Re: Transmission questions...

Quote:
Originally Posted by SixtyAte View Post
Brent,
The 3925656 is as follows;

Saginaw M20 68-69 3925656 2.54 1.80 1.44 1.00 V8 engine


What if any rings are on the input shaft? The 2:54 first is like my ST-10 2:28 second!

Kev
I haven't pulled the tranny yet, everything is still in the car, so I don't know how many rings there are.

But wow, that's hard to believe that it's a 2.54. I feel like I'm shifting halfway through the stoplight right now.

FWIW, I don't believe the tranny is original to the car. Any chance that a later transmission could have the same id number with a different ratio?

Last edited by 67Rally; Nov 25th, 12 at 06:22 AM.
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  #8  
Old Nov 25th, 12, 06:40 AM
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Kevin
 
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Default Re: Transmission questions...

Saginaw 4 speeds are id'd as follows:

no rings= 2.84-2.01-1.34-1.00
1 ring = 2.54-1.80-1.44-1.00 (very common ratio)
1 ring = 2.54-1.80-1.32-1.00 (very rare ratio)
2 rings = 3.11-2.20-1.47-1.00
3 rings = 3.50-2.46-1.65-1.00


Kev
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  #9  
Old Nov 25th, 12, 07:45 AM
Melrose RS Melrose RS is online now
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Default Re: Transmission questions...

Quote:
Originally Posted by 67Rally View Post
I haven't pulled the tranny yet, everything is still in the car, so I don't know how many rings there are.

But wow, that's hard to believe that it's a 2.54. I feel like I'm shifting halfway through the stoplight right now.

FWIW, I don't believe the tranny is original to the car. Any chance that a later transmission could have the same id number with a different ratio?
Now the bad news is a Muncie M20 is going to feel exactly the same.
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'67 rs - ordered new by my Grandfather
327 L30, K-K, Deluxe int, tach & gauges, 12 bolt posi, 4 speed.
the Melrose rs - L30 327/275hp
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  #10  
Old Nov 25th, 12, 08:24 AM
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Kevin
 
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Default Re: Transmission questions...

Quote:
Originally Posted by Melrose RS View Post
Now the bad news is a Muncie M20 is going to feel exactly the same.
Tom,
Sure is ....provided that he has the same first gear. To me it sounds like my ST-10 and its 3:42 first. The chart I posted shows it could have the 3:11 or the 3:50 first! A M21 would give him a 2:20 first which would be much better and be like taking off in second with the Saginaw now.

Kev
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  #11  
Old Nov 25th, 12, 09:55 AM
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Brent
 
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Default Re: Transmission questions...

As Tom already knows, one of the reasons for the engine rebuild is that my car really dies off after 4k rpm. I have spoken with a couple of engine guys, and after describing my symptoms it sounds like it could be a combination of valve float and low compression (rings ?).

I'm wondering if the sensation of a granny gear is in part because I'm revving to 4k so fast and having to shift soon because of the engine limitations and not the gearing?

Once I pull the engine, I'll know what I have for a first gear ratio. I'd love to see how the 383 feels with my current gearing and then make a transmission decision based on that. But it would be much easier to install the new engine and tranny as one piece.

Based on the above numbers, 2.54x3.31=8.40, I should have plenty of first gear, almost too much right?
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  #12  
Old Nov 25th, 12, 05:03 PM
Melrose RS Melrose RS is online now
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Default Re: Transmission questions...

Ya know... we could just jack it up, put it in first and turn the engine over 2.5 times and see if the driveshaft turns once. That would prove a 2.5 first gear.
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327 L30, K-K, Deluxe int, tach & gauges, 12 bolt posi, 4 speed.
the Melrose rs - L30 327/275hp
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  #13  
Old Nov 25th, 12, 05:31 PM
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Brent
 
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Default Re: Transmission questions...

Quote:
Originally Posted by Melrose RS View Post
Ya know... we could just jack it up, put it in first and turn the engine over 2.5 times and see if the driveshaft turns once. That would prove a 2.5 first gear.
Isn't it the other way around?

***Edit***

Nvm. I was thinking about rear end ratio.
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  #14  
Old Nov 26th, 12, 02:56 AM
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Kevin
 
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Default Re: Transmission questions...

Brent,

How old is the 383 since being built? Has it ever run powerful? Have you done a compression check? Have you tried a different distributor and coil setup? Are you running a MSD system? There have been issues with the MSD setup where they are fake, made in China and have no components like the real box! It should not did a 4 grand no matter what because the final gear of 1-1 is the same no matter what you start of with (3:42 or 2:50 )in first. As far as valve float...were stiffer springs installed when the heads were built? Stock springs will not cut it for sure. I would check the numbers off them to be sure. Also recheck where you are at #1 compression stroke as compared to the position on the cap...and check overall timing If using vacuum advance, look there also....could be way out Just some ideas before tear down of a possible good engine.
Kev
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  #15  
Old Nov 26th, 12, 03:07 AM
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Brent
 
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Default Re: Transmission questions...

Quote:
Originally Posted by SixtyAte View Post
Brent,

How old is the 383 since being built? Has it ever run powerful? Have you done a compression check? Have you tried a different distributor and coil setup? Are you running a MSD system? There have been issues with the MSD setup where they are fake, made in China and have no components like the real box! It should not did a 4 grand no matter what because the final gear of 1-1 is the same no matter what you start of with (3:42 or 2:50 )in first. As far as valve float...were stiffer springs installed when the heads were built? Stock springs will not cut it for sure. I would check the numbers off them to be sure. Also recheck where you are at #1 compression stroke as compared to the position on the cap...and check overall timing If using vacuum advance, look there also....could be way out Just some ideas before tear down of a possible good engine.
Kev
Kevin, the 383 hasn't been built yet. The current engine is a 350 that came in the car when I bought it. It's an early 90's truck engine out of a K series truck. I installed a new cam, some Vortec heads, and Performer RPM intake last winter. I installed a new set of the LS6 beehive springs in the heads at that time. The heads were used but "in great condition", and I did not shim the springs, I just installed them as is. The original heads that came off my engine were caked in sludge.

Tom helped with the camshaft install and also dropped the original distributor in for me.

I installed a new carb over the summer (Edelbrock 650 TVS) as wells as a new DUI distributor custom curved to my setup and a new set of plug wires at the same time. No MSD setup.

It will pull hard to 4k and then climb to 5k but it sounds like it's struggling bad from 4-5k. I have not done a compression check on it.

I've had a couple different threads going over the past few months and tried just about everything (timing, vacuum, carb, dizzy, etc) and eventually everyone gives up posting suggestions.
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