overdrive trans comparisons

[696pack]

Although I have not bought one yet (and will eventually for my 6 pack bee) I have always been an advocate for Passon's 4 speed overdrive rather than the 5 speed or 6 speeds available.

I just don't understand the big facination with the 1 or 2 extra gears.

For those that want more top end, how much can you use? There are few wide open spaces that you can safely drive 150 mph+ and if you get caught these days you can lose your car and go to jail. The areo dynamics of our old cars make it difficult as well.

I suspect that many want an overdrive for the same reasons I do, to reduce engine wear and for an attempt at improving mileage. If you are only looking at one of these then you better figure out how many miles per year you plan to drive your car and do the math as to how many years you are going to have to drive it just to break even on the cost of conversion.

The Passon 4 speed overdrive does not require a different shifter or any other parts to replace your existing trans except for a different clutch disc if you have a 23 spline rather than an 18 spline trans. Unless you are the one driving the car or a passenger watching the tach on the 3rd to 4th shift no one ever suspects you have had a modification to the trans.

With a 5 speed Passon you at least have to buy a new shifter mechanisum and I have not researched it for possible other items needing replacement such as the above mentioned clutch disc for the 4 speed.

With the Tremac conversions we all know there is MUCH more to buy and invasive modifications. These mods may not be a big concern for the pro touring types but I don't want those types of invasive mods to MY car.

Below is an easy comparison of the Passon 4 speed/over drive and the 5 speed. I don't see enough difference to justify the extra gear. I also like the fact that with my car/engine/rear combo (1969 6 pack bee, 523 stroker, 4.56 gears) that with the 4 speed overdrive I will be running throug the 1/4 in 3 gears just like an auto trans and one less possible gear to miss. You will note below that the first 3 gears of the passon 4 speed overdrive are nearly identical to an auto trans 727.

Gearset TireSize RPM Speed Rear End Ratio
Stock 1:1 28“ 3248 65 m.p.h. 4.10 : 1

Passon Performance
Overdrive .80:1 28“ 2580 65 m.p.h. 4.10 : 1



4 speed overdrive gear ratios 5 speed

1st 2.65 : 1 2.66 : 1 2.64 : 1

2nd 1.93 : 1 1.59 : 1 1.92 : 1

3rd 1.39 : 1 1.00 : 1 1.40 : 1

4th 1.00 : 1 .80 : 1 1.00 : 1

5th 0.70 :




Passon 4 speed/overdrive unit
Stock Rear Ratio
(1:1 4th Gear) Adjusted Rear Ratio
with Overdrive
3.23 : 1 2.58 : 1
3.54 : 1 2.83 : 1
3.55 : 1 2.84 : 1
3.91 : 1 3.13 : 1
4.10 : 1 3.28 : 1
4.56 : 1 3.65 : 1

 

[Cranky]

Missed gears? Good drivers with good equipment don't miss gears I like close ratio 4 speeds so I'd be going for the extra OD gear.....

 

[696pack]

Missed gears? Good drivers with good equipment don't miss gears I like close ratio 4 speeds so I'd be going for the extra OD gear.....

I agree. I don't think I have missed a gear in 40 years but I AM getting old.:3gears:

 

[Revhendo]

I've done a fair amount of 5 speed conversions. For a Mopar, I would definately go with the Passon unit. He's done his homework on it and it is a very well thought out set up. You're right about the Tremec based kits requiring some major mods. It can be really vicious on an A body.

Understanding that the 4spd OD unit and the 5spd OD both get you an overdrive ratio, the big factor is in the split in the gears. With the 5 speed unit, you're keeping your engine in a better powerband with less RPM drop between gears. OK, that's the technical end of it. It's kinda like if you do a full throttle boogie and every gear has it's sweet spot, 'cept when you're cruising around you always feel like you could use one more gear. There's that 5th one working for you.

Sorry I can't explain it better right now, I worked all day and I'm wiped.

 

[72Fourspeed]

Passon

In a review/preview of the Passon 5 speed,it was stated that the Passon 5 speed would come with the linkage. Just screw on your shifter ball & go. Supposed to be an absolute bolt in, stock speedo hookup,everything.
For what it`s worth,I been down this road twice on other vehicles. I had a 6 speed conversion done on my Harley.Best mod done to it so far. Dropped rpm almost 600 when you are at 75 mph. I also did a tranny swap on a half ton Ford I owned years ago. Went from 3 speed/3.50 rear to 4 speed OD/3.50 rear.Too much rpm drop for me. Ended up with a 4 speed granny/3.00 combo and a little tire swapping. Best for my needs. You have to figure what you need to accomplish & balance gear/rpm/overall tire diameter. That said,you have to love the idea of that Passon 5er.

 

[696pack]

No explaination needed Revhendo I do understand the gear split differences.

As 63postcar mentioned "You have to figure what you need to accomplish & balance gear/rpm/overall tire diameter." I will take this a step further and say that you have to do what is right for you, your car, and for what you want to accomplish.

For me it is about creating a good all around car for both daily and strip driving. With my 523 stroker engine and 4.56 rear gears it is not exactly street friendly except with it's intimate relationship with the gas station. I plan to drive this car fairly often and living in AZ. I am aslo converting the car to a factory A/C interior for comfort. I may also add aftermarket power windows. I know, not exactly what an A12 was meant to be from the factory but hey I have come to appreciate these thing as well as being a gearhead why can't I have both?

There is certainly nothing wrong with the gear split of a 727 as they are typically faster in identical cars sans the trans.

My purpose is to have a car that when viewed at the parking lot show and they are looking under the hood and at the numbers they are saying "it is a real A12 but where are these extra hoses going?" on further inspection they will see a hidden low slung A/C compressor that also allows for the original air cleaner base. When they look inside the car they will see factory A/C vents and controls and a pistol grip shifter (1970 but a WAY better shifter than the 69) with the standard 4 speed pattern. If they get a ride in the car they will note that the car will be pulling with a lot of power put to the ground through the 4.56s in the first 3 gears which is EXACTLY what I need for racing but will cruise on the highway like it has between 3.55s and 3.73 rear gears.

I want a car that will make people scratch their heads when looking at it and riding in it.

I want a car that I can race with respectable power/speed.

I want a car that is comfortable to drive in hot weather on the highway.

I want a car that even though uses a lot of gas doesn't necessarily break me at the gas stations over a course of the year.

That is why at this point my vote is for the Passon 4 speed overdrive for MY car.

Certainly there are others with different combos and different purposes for their cars that the 5 speed will be better suited for them.

 

[Meep-Meep]

I too went with the Passon OD 4 spd. in my old 18 spline box however I don't have it running yet. But it's together and ready to go. Assembly was a little different because you need to have the cluster lying on the bottom of the case as you assemble the main shaft and the case.

I believe having a big gear spread requires a cam that is not so peaky. With a big inch engine you can run a 114 deg LC cam to spread you torque over a broader RPM range, which will make you car do everything you want it to do. Even though the TF and the Passon OD 4 spd have similar ratios the TF still has torque multiplication in the converter so I'm not sure if that's a fair comparison. I look at the Passon tranny as more of a three speed manual but with better ratios.

 

[696pack]

I too went with the Passon OD 4 spd. in my old 18 spline box however I don't have it running yet. But it's together and ready to go. Assembly was a little different because you need to have the cluster lying on the bottom of the case as you assemble the main shaft and the case.

I believe having a big gear spread requires a cam that is not so peaky. With a big inch engine you can run a 114 deg LC cam to spread you torque over a broader RPM range, which will make you car do everything you want it to do. Even though the TF and the Passon OD 4 spd have similar ratios the TF still has torque multiplication in the converter so I'm not sure if that's a fair comparison. I look at the Passon tranny as more of a three speed manual but with better ratios.

Back in the old days (1970) they said that the Mopar 3 speed had a better gear spreed for racing than the 4 speeds.

 

[Meep-Meep]

Back in the old days (1970) they said that the Mopar 3 speed had a better gear spreed for racing than the 4 speeds.

Well, they ran Max Wedges with three speeds so they couldn't have been all that bad.

I made an excel spread sheet showing the ratios and the RPM drop in each gear from 6000 RPM and 3000 RPM. The gear spread on the OEM unit is about 28% and the Passon is 35-40% if I remember correctly (spread sheet is on another computer). I'm going to run a 112 LC cam with a factory six pack so I'm not too worried about it.

 

[FridayGt]

Sorry to resurrect an old thread, but this is exactly what I've been thinking about for down the road. I'm going to throw bigger (numerically) gears in my car, but still want to be able to cruise the highway. I love the idea of a 4-speed, but I'm not sure if I'm up for the big expense and extensive modification. Besides, being able to manually ratchet through the gears in an automatc when you want to isn't so bad! I want to be able to put a lot of power through better ratio gears in the back, but still be able to comfortably cruise the highway on that nice weather Friday drive to work.

If you don't mind my asking, what was the overall cost this change set you back? I'm not talking rear diff's or shifters, just the cost to pull your 727 out and put this one in? What all apart from the trans did you need to pick up for this conversion?

Also, how is your 4th OD gear engaged? Automatically? Via shifter or switch under dash?

Finally, how has it stood up over the last 6 months? Have you raced with it? Were your times affected? Have you had to do any additional maintenance or repair? How has it handled the power compared to other over drive tranny's that I hear can't?

I know these are probably pretty simple questions, but I'm on the low end of the experience spectrum, so I appreciate the help.

 

[shag766]

i have the tremec 5 spd behind the hemi and i like it. the mods i thought were minimal. i run 3;90 rears. the tremec in 1st gear is equivlent to 4;30 ratio, approx. at 65 mph i am reving at 2100 rpm.

 

[FridayGt]

i have the tremec 5 spd behind the hemi and i like it. the mods i thought were minimal. i run 3;90 rears. the tremec in 1st gear is equivlent to 4;30 ratio, approx. at 65 mph i am reving at 2100 rpm.

What modifications did you have to do if any to put it in? Was it a direct swap?

I didn't realize they had a 5 speed auto. Cool, what are the details on that? Cost? What all did you have to change?

 

[shag766]

tremec

What modifications did you have to do if any to put it in? Was it a direct swap?

I didn't realize they had a 5 speed auto. Cool, what are the details on that? Cost? What all did you have to change?

x
it is a 5 spd std. the only mod was to cut a 5"x5" hole in the tunnel. i cut it exactly and would be able to reinstall it if i wanted to. it requires a shorter drive shaft also.

 

[moperformance]

i have the tremec 5 spd behind the hemi and i like it. the mods i thought were minimal. i run 3;90 rears. the tremec in 1st gear is equivlent to 4;30 ratio, approx. at 65 mph i am reving at 2100 rpm.

I put a tremec 5 speed in my 64 fury and it was the best single thing I've done to the car! It took major surgery on the trans tunnel and the only bitch I've got is that the shifter comes out under the dash and even with a creative bend in the shifter I have to sit close to the steering wheel since the shifter ball isn't in the stock location. Kiesler said it was a drop in and they really didn't have a clue as mine was the first or second kit they sold years ago. BUT all that aside I absolutely love rowing through 5 gears and running 65mph at a little over 2 grand puts a smile on my face every day as I have a 60 plus mile round trip to work 4 days a week. One day I'll have to find out what top end is :headbang: