[azbirds]

3.42's seem like a great gear for that trans. Mine is a 72 T/A with the 455HO, mild cam, stock manifolds, Cliffs Q-jet, Pypes 2.5 with x and transverse muffler. My factory tech is goofing up right now so I don't know the rpm's. Before the swap, if I was going over 50 and slightly let of the gas the car would immediately start slowing down, not with this new trans. I am having issues with the shiftworks detents in my stock shifter not matching the transmission detents. Has anyone figured out the linkage to make these two play well together?

[hgerhardt]

I've got 3.73's in my '66 GTO with 428 and 26" tires and non-lockup 10" converter. I'd go a little less, like 3.42's next time. As it is now, with 255-section tires, I still get wheelspin at any speed below 55 mph (which is 2nd gear). So it's a bit ridiculous on the street.

[Navy Horn 16]

I've got the 3.42s and haven't conquered the wheel spin issue. Torque is a hell of a drug.

[azbirds]

Post #14 used 2.93 gears and still has wheelspin! Torque baby!! Someone could drop in some 2.41's and go to Bonneville with it.😁

[azbirds]

I'm having problems with the shifter detent matching the detente on the transmission. I'm using the shiftworks parts in a stock shifter. Has anyone else had this problem and what was the fix?

[Navy Horn 16]

Originally Posted by azbirds

I'm having problems with the shifter detent matching the detente on the transmission. I'm using the shiftworks parts in a stock shifter. Has anyone else had this problem and what was the fix?

I had the same problem. This is the fix:



Make sure you get the B&M cable and shifter brackets, including the arm that goes on the transmission.

The Shiftworks parts don't work.

[Steve C.]

I use the same shifter from B&M.


.

[Bobalong]

Originally Posted by azbirds

I'm having problems with the shifter detent matching the detente on the transmission. I'm using the shiftworks parts in a stock shifter. Has anyone else had this problem and what was the fix?

After massaging the linkage and cable and hours of adjusting I got my
shiftworks shifter to do everything EXCEPT still can't start engine in N.

I bought their cable.

[azbirds]

I'll start messing with the arm length because I just don't like the way those shifters look, especially for a 72 T/A. I have an advantage since I run a machine shop and can build anything I need.

[455'73inElCamino]

I have been running 3.73 gears and due to some rear end vibration, will have the opportunity to change gears.

Anyone swap from 3.73 to 3.08 and wish that they didn't?

[T/A addict]

No one here mentioned 4.10 gears...... guess that even with the OD 4.10 gears suck?

[Cliff R]

Pick the gears for best vehicle performance based on the 1 to 1 third gear ratio and let the rest sort itself out.

Here is the formula I use here: MPH x GEAR RATIO x 336 divided by tire diameter times the OD or 4th gear ratio.

For example, 55MPH x 3.42 x 336 divided by 26" puts the engine at 2430 rpms at 55mph. Multiply 2430 x .67 and you'll be at 1628rpm at 55mph in OD or 4th gear.

Plug in 70mph and those numbers change to 3093rpm and 2072 respectively.

For the 700-R4/4L60's with it's .70 OD the engine will be at 2430 and 1701 @ 55mph and 3093 and 2165rpms @ 70mph.

If you are drag racing the car and it's got the power to run decent MPH, you might want to plug those numbers in as well to make sure you don't put too much gear in the car and run out of motor on the top end of the track.

For my car I'd plug in 120mph x 3.42 x 336 divided by 26 so would go thru right at 5300rpm's.

None of these formula account for converter slip, so if you are using a non-LU converter there may be a few more RPM's seen at every point, but with a good converter it woln't really be enough to worry about.....Cliff

[455'73inElCamino]

Cliff, that is the analysis that I typically do.

But, since I have lost a fair amount of interest in going to the track, primarily due to lack of time, I was wondering if anyone who has dropped from a high gear ratio to a lower one (for better highway cruising) missed the acceleration far more than the comfy "highway" gearing and wish they never did the conversion.

My car has had 3.73 gears for a long time but my car has not had any issues with cruising at 2500 rpms for long periods of time. I am just agonizing over choosing a better cruising gear vs 3.73.

[JLMounce]

For a cruiser, I don't honestly know if you'd really notice it all that much. No it's not going to be as quick off the line, but I just don't see it making that large of a difference. Your starting line ratio changes from 10.22 to 8.44 and since you've got a torque converter helping you out, it shouldn't be too much of an issue.

If you're really worried about it, you could split the difference and go to something like a 3.36 which gets your starting line ratio to 9.20.

The one thing that you may want to determine is where your engine may or may not have an inherent drone or odd cackle that you may wish to avoid while cruising. Not all cars will exhibit such behavior, but lets say that you have a good bit of drone at 1700 rpm. Using Cliff's suggested math, going with a 3.08 and your 200r4, would put your 70mph cruise right in that zone. While the rpm may be lower and ostensibly "better" for cruising, you may find the car is actually making more noise which may wear on the driver.

Just something to think about.

[ta man]

Originally Posted by 455'73inElCamino

I have been running 3.73 gears and due to some rear end vibration, will have the opportunity to change gears.

Anyone swap from 3.73 to 3.08 and wish that they didn't?

I assume no overdrive? You may lose a little acceleration at lower speeds or from a stop but on the highway the car will feel faster.

[Cliff R]

Tire diameter is a big player, so I recommend using the formula I supplied above when trying to "target" you RPM's at any give speed in 3rd and 4th.....Cliff

[455'73inElCamino]

I am running the 2004r which is why I posted under this thread. So I do have an overdrive.

So I have elected to go to a 3.42 which is not a big change but will get my speedometer corrected. Not a great reason to change it but it keeps me "close" to the 3.73.

At this time I guess I am not really ready to drop the RPM a lot for highway cruising speeds.

10 years from now "they" might not even allow us to use gas powered cars and cruising will be a non issue.

[footjoy]

I am curious to know what gas mileage your getting with 3.73 and your 2004r?

My 400 2004r with 3.73 get 11 mpg.

Greg

[455'73inElCamino]

Originally Posted by footjoy

I am curious to know what gas mileage your getting with 3.73 and your 2004r?

My 400 2004r with 3.73 get 11 mpg.

Greg

I have been getting 13-14 MPG.

[Cliff R]

Those numbers seem really "low" to me.....FWIW.....