Old School vs. New School Differential Gearing

[robbie_d68]

So, I have a question as far as Rear Differential Gearing.

Background: I currently have a 1972 C10, 350 SBC (1992 crate engine), 700r4 Auto Trans (1992), 3.73 gears (we think), long wheel base.

I have a 2007 Ford Edge with a V6. I have a quicker take off speed with my ford edge and I have a lower/smoother cruising RPM with my ford edge.

Question: how can a smaller engine, run smoother at higher speeds (80-90 MPH) than a bigger engine? I know there is a lot of discussion on here regarding rear differential gearing, so why is the current gearing ratios on vehicles today are so much better than the older models? I can run all day long in my Ford V6 at 80-90 MPH, but at 80-90 MPH in my C10, I am worried about messing something up. I do not have a tachometer on my truck, I am just going by sound.

Any advise would be greatly appreciated. I am looking at my next purchase to be gearing if I decide to change it.

[special-K]

Nothing to do with gearing. Engine-wise you are comparing apples to oranges/ old school to new technology/ carburetor to FI, etc. Engines give more from less these days. The broader available torque, the taller gearing you can run. Compare a 5.3 LS to a 327

[Mike C]

Some of it is gearing. How many speeds are in your new cars transmission? Typically they have way more total numeric multiplication in first gear AND they have more overdrive.

And manufacturers have spent a ton of time and money on reducing noise, vibration, and harshness (NVH).

Go drive a brand new GM V8 powered truck with the new 8 speed transmission in it.

[robbie_d68]

Originally Posted by special-K

Nothing to do with gearing. Engine-wise you are comparing apples to oranges/ old school to new technology/ carburetor to FI, etc. Engines give more from less these days. The broader available torque, the taller gearing you can run. Compare a 5.3 LS to a 327

It is just very frustrating when you pay $2K+ for a new transmission and have a 350 SBC that sounds awesome, but you cannot even stay up with a Toyota Yaris starting from a stop light.

[robbie_d68]

Originally Posted by Mike C

Some of it is gearing. How many speeds are in your new cars transmission? Typically they have way more total numeric multiplication in first gear AND they have more overdrive.

And manufacturers have spent a ton of time and money on reducing noise, vibration, and harshness (NVH).

Go drive a brand new GM V8 powered truck with the new 8 speed transmission in it.

6 Speed Automatic for my Ford, 4 speed with OverDrive for my Chevy. 8 SPEED Transmission? Wow, had no idea they had that many gears in trucks today.

[robbie_d68]

..

[geezer#99]

Originally Posted by robbie_d68

It is just very frustrating when you pay $2K+ for a new transmission and have a 350 SBC that sounds awesome, but you cannot even stay up with a Toyota Yaris starting from a stop light.

Sux, doesn't it!!
I blew off a challenger srt8 from a light here on the big Island highway with my wifes Kia 4 banger! I had him right up to 140 kph (85 mph) until he finally got up to full warp!
It was hilarious!!

[RustyBucket]

I dunno, with a 3.06 first gear ratio and a 3.73 rear gear your truck should jump off the line pretty briskly.

[RustyBucket]

Originally Posted by robbie_d68

It is just very frustrating when you pay $2K+ for a new transmission and have a 350 SBC that sounds awesome, but you cannot even stay up with a Toyota Yaris starting from a stop light.

Still thinkin' about this thread.... when you're next to this YARIS, what happens when you slap the gas pedal real hard from a standing stop? Your awesome sounding 350 should blast the right rear tire if you don't have a posi rear or maybe both of 'em if you do.. depending how awesome it really is. I looked up a road test on an '07 Ford Edge and they claimed a 16.0@87mph quarter mi. which is respectable for a truck or SUV but not FAST. I'd think a '67-'72 with a good runnin' 350 with a 700r4 & 3.73 gears should have comparable or better performance.
Don't mean for this post to sound argumentative, just feel like my old trucks keep up with traffic pretty good. Both have OD transmissions and I cruise 'em 70-75mph on the interstate. They don't have late model safety features or stop, handle great, but they do GO pretty good.

[TwoFiftyShifter]

I have the same axle ratio without overdrive and I can run 70mph without much NVH considering the truck is 45 years old.

Don't compare it to new though.

[special-K]

I guess I meant more about modern engine vs old school than gering. We have no info on your Fords gearing to even compare and all we know is your 350 is a crate engine. Who's crate? Stock for '92? Carb, cam, compression, any specs at all to share? Everything is fast today. Faster than the average person should have available, and more than needed. people pull out of lights like a bat out of hell, even when they aren't in a hurry. They are moving out in a way only us guys who had hotted up stuff used to and got evil looks... and tickets!

Also, the 700r4 has a pretty low geared 1st. It's great for your truck, but doesn't grab a lot of speed for you real quick.

On Big Twin Harleys they put the same first gear as heavy full dressers in all of them. I put a taller first when I blueprinted the trans and my FLST weighs about 200# less. I can run another bike with matched HP and dust his but off the line. Mine lunges out ahead and stays there. It baffles them... since all they want to talk about is what they have for motor. I don't feel it's my responsibility to enlighten them on transmission specs (back-cut gears and other goodies don't hurt either) So it is about gearing in that scenario.

[robbie_d68]

Originally Posted by RustyBucket

Still thinkin' about this thread.... when you're next to this YARIS, what happens when you slap the gas pedal real hard from a standing stop? Your awesome sounding 350 should blast the right rear tire if you don't have a posi rear or maybe both of 'em if you do.. depending how awesome it really is. I looked up a road test on an '07 Ford Edge and they claimed a 16.0@87mph quarter mi. which is respectable for a truck or SUV but not FAST. I'd think a '67-'72 with a good runnin' 350 with a 700r4 & 3.73 gears should have comparable or better performance.
Don't mean for this post to sound argumentative, just feel like my old trucks keep up with traffic pretty good. Both have OD transmissions and I cruise 'em 70-75mph on the interstate. They don't have late model safety features or stop, handle great, but they do GO pretty good.

Not argumentative, just asking questions. If my truck was properly done, it may be better. I just do not know what to do to make it better.

If I hit my gas, it goes, but it is not quick at all. The RPM's rise, but the truck begins to pick up speed slower than expected. There is no burning rubber or chirping the tires. Inside, it feels pretty weak, outside with glass packs and dual exhaust, it sounds pretty good. My co-worker has a 07 Silverado and has worked on trucks before. He says my truck just doesn't feel right.

Again, we are not sure if it is gearing or the transmission is messing up.

[Bigdav160]

You've got to keep in mind that modern car drivetrains are heavily engineered to get that type of performance. It's not just gearing.

[Mike C]

With 3.73 and 3.06 it has gear. Now you need more converter and more motor and less weight.

New cars are amazing performance wise even if they are visually less than interesting.

Even in the 80's the little front wheel drive 100 hp cars were impossible to hang with from a dead stop. Once you hit 35 or so it was all over, but an interesting lesson in mass.

[robbie_d68]

Originally Posted by special-K

I guess I meant more about modern engine vs old school than gearing. We have no info on your Fords gearing to even compare and all we know is your 350 is a crate engine. Who's crate? Stock for '92? Carb, cam, compression, any specs at all to share? Everything is fast today. Faster than the average person should have available, and more than needed. people pull out of lights like a bat out of hell, even when they aren't in a hurry. They are moving out in a way only us guys who had hotted up stuff used to and got evil looks... and tickets!

Also, the 700r4 has a pretty low geared 1st. It's great for your truck, but doesn't grab a lot of speed for you real quick.

On Big Twin Harleys they put the same first gear as heavy full dressers in all of them. I put a taller first when I blueprinted the trans and my FLST weighs about 200# less. I can run another bike with matched HP and dust his but off the line. Mine lunges out ahead and stays there. It baffles them... since all they want to talk about is what they have for motor. I don't feel it's my responsibility to enlighten them on transmission specs (back-cut gears and other goodies don't hurt either) So it is about gearing in that scenario.

I know nothing about my crate engine. I have only had the truck a month and have not torn it down or had it tested. 4 BBL Carb. is all I know. I did not know about the low first gear of the 700r4, that is something good to know now. Thank You for the information!

[my67c20]

Your last post sums it up pretty good, that you "know nothing about your crate engine". Sounds like maybe its time to freshen things up. When was the last time it was tuned up? Have you checked the compression? Hook a vacuum gauge up, what is that doing? How much staining is around the carburetor gaskets? What size tires? That combination should at least be good for some tire chirping. Granted its not going to have the snap off the line like most modern vehicles, but she should get up and go.

[geezer#99]

Gotta agree on that crate!!
Likely poor combo!
Low compression.
Poor heads.
Poser cam(all noise, no action).
Poor timing curve.
Doesn't much matter what tranny you have, it'll be struggling to get out of it's own way.

[RustyBucket]

Robbie, lets see some truck pictures... everybody likes 'em. Maybe a sound byte too. Somebody on here might have some good info for you on improving your truck's performance. May be just a tuning issue. Guy brought me a '68 Camaro years ago that ran and sounded ok but was SLOW. Somebody had installed a GM HEI distributor that had no vacuum or centrifugal advance. Changed distributors and it was a different car. Your truck running right should be kinda fun to drive and pull at least as strong as your FURD SUV.

[GASoline71]

2 words... "1992 GM crate engine".

Your truck also weighs 4,000+ pounds.

Your expectations for a stockish V8 in a heavy truck with an OD is a little too much.

Gary

[davepl]

Since I was planning to run an overdrive trans (first a 200-4R, now a 4L80E) I went with steeper rear gearing - 4.10s I believe. That, combined with the steep first gear means I have plenty of low speed torque and yet I still have overdrive.

More gears is nice, but the spread in between lowest and highest is likely more important. Within reason, of course... that crazy 4-speed in these trucks would be an exception.

I wonder with that four speed if you could run 2.56s and actually make use of first gear (I always just started in 2nd when I had one).

When my motor is more broken in I'll have to do a 0-60 time test. I think my Dad's old 307 was 16 seconds, so I wonder if I can break 10 with the 396?

[outfield]

Robbie,

I would start with a full tune up. Plugs, wires, cap and rotor. Are you running points or HEI? If you have points, consider an upgrade to HEI for a hotter spark.
Is your vacuum advance working? Search on the forum to find out how to check this.
Have you checked the timing? If your timing is retarded, you are not making power! Just a timing adjustment can make a world of difference. I just adjusted my timing from 2 degrees to 8 degrees and was surprised at the difference in power. Many guys on the forum are running up to 12 degrees, do some searches.
Good luck!

[special-K]

I've never been able to get an apple to taste like an orange

[garyd1961]

I have a 70 C10 long bed, L31-R crate 350, th350 trans, 3.07 gears. It looks like an old farm truck and I get my kicks by leaving the younger guys with their little japan cars sitting at the light. Sometimes I just keep up beside them so I can see the look on their faces, lol. I can still cruse 75 with no problem at all.
To the OP, you need to have figure out what motor you have, then make sure it's tuned right . If it still lacks power you can either upgrade heads, cam, intake and carb or just get another motor. Of course you could just keep on driving as is.

[RustyBucket]

Talking about new/old technology, here's a link to the mechanical specs on your Ford Edge ... http://www.myfordedge.com/specs/2007...ifications.php

interesting number comparison to our old trucks

[Mike C]

2.77 final drive and 4.48 first gear is a 12.42 overall first gear ratio. That is equal to 4.05 with the TH700.

That's one reason. The high rev limit, high compression is really a performance engine even if it is in a pedestrian application.

To get the same performance from the truck, you just need a performance engine. Most likely your crate motor just an 8.5:1 replacement truck engine. 240 hp which is really pretty much the same as a mid 70's 185 hp L-48.

Interesting read, thanks for posting that link.