Opinions on 4 speed with OD

Phreakish

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@AJ/FormS

28 inch tires fit. Larger of you roll the lip. “assumptions”, key word, often a mistake, this is why it’s not wasting a post since better information cuts down on your long winded posts that don’t help as well as you think they do.

And the mighty Bible thumper has failed again !!!!

You should get your head out of your ass & out of the calculators and actually do some wrenching.

Tell us (really lie) again how you get 38 mpg’s from your 7,000 shift point 360.

My dart runs a 25.5" tire. The absolute largest I could fit would be around 26.5, and it would rub at ride height, let alone with some compression. I've moved my rear end back about 1/2" to make enough room for some tires that are available in a~27" height though. A 28" absolutely will not fit, even with rolling on my car. I'd have to clip the front edge of the opening.
 

rumblefish360

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My dart runs a 25.5" tire. The absolute largest I could fit would be around 26.5, and it would rub at ride height, let alone with some compression. I've moved my rear end back about 1/2" to make enough room for some tires that are available in a~27" height though. A 28" absolutely will not fit, even with rolling on my car. I'd have to clip the front edge of the opening.
That would have been excellent in the first post because the more information available there is the quicker you can get an answer. Just saying, not bashing.
Different size wheel wells on different cars create different outcomes.

An example is a Duster which can take a 28” tire and if anyone wanted to go to a 30 inch, there is a little metal work to be done in front of the tire. Some consider that a big deal in ether work load or they don’t want to ruin the car in that fashion.
 

Phreakish

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That would have been excellent in the first post because the more information available there is the quicker you can get an answer. Just saying, not bashing.
Different size wheel wells on different cars create different outcomes.

An example is a Duster which can take a 28” tire and if anyone wanted to go to a 30 inch, there is a little metal work to be done in front of the tire. Some consider that a big deal in ether work load or they don’t want to ruin the car in that fashion.

100% Agree. More info is always better than less.
Since different cars can take different tire sizes, and different cams/builds can change the target cruising RPM, this thread is a lot of shooting in the dark.. lots of members have contributed a ton of useful info, but since OP omitted so much it's not as constructive as it could be.
 

rumblefish360

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Yep! Often the case and that’s OK, it is what it is.

I just don’t see a point in a long winded post with absolutes when non of the math could possibly work since I would be a matter of getting a dart thrown on the board and not the wall when drunk, blind folded and in the dark after being spun around 30 times.

But of course AJ is well versed in that.
 

Steve welder

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383 engine, 355 rear ratio, tires 25 inches tall
Comp cam .477 lift intake .480 lift exhaust
I called Passon and left message
If the first to second shift is acceptable I might go with that trans or have him do mine over
Thanks again
 

Darter6

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I'd have to clip the front edge of the opening.
Yeah, I had that problem on my 67 Dart.
Just a thought,,I'm pretty sure that both Passon and Brewer would do the 23 spline or a 18.
Ours from Passon was a 23 spline.
 

dodgedifferent2

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Do you know the specs on your cam?

lunati 40200734
Advertised Duration (Int/Exh): 285/293; Duration @ .050 (Int/Exh): 255/263; Gross Valve Lift (Int/Exh): .600/.600; LSA/ICL: 110/106; Valve Lash (Int/Exh): 016/016; RPM Range: 3200-7200

Installed lunati 40200733 now
 

Ivan Baez

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I have a manual 4 speed with 1:1 final gear and 2.7 ratio at the differential. Very good for cruising speeds. the 426 stroker has enough torque to push you back at any gear and wheel spin is minimized.
 

jos51700

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Can we define 'abuse' in terms of what kills the aluminum case a833's? Is it burnouts and clutch drops? Lots of shifting loading and unloading the countershaft? Heavy downshifting? Or...?

I've little experience with them (and own at least three of them), but seems to me it would do fine even in a high torque car if you're running mild street tires and aren't clutch dropping frequently, but I don't really know.

In a street car driven reasonably most of the time, I'm wondering if it would really have trouble keeping up.
 

gzig5

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Can we define 'abuse' in terms of what kills the aluminum case a833's? Is it burnouts and clutch drops? Lots of shifting loading and unloading the countershaft? Heavy downshifting? Or...?

I've little experience with them (and own at least three of them), but seems to me it would do fine even in a high torque car if you're running mild street tires and aren't clutch dropping frequently, but I don't really know.

In a street car driven reasonably most of the time, I'm wondering if it would really have trouble keeping up.

The issue with the aluminum case is the lower shaft is a loose fit in the case which allows the gears to move in relation to each other under high loads that wouldn't affect the steel case. The case can be modified with a bushing that tightens up the fit and gives the same performance as the steel cases.
 

DionR

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The issue with the aluminum case is the lower shaft is a loose fit in the case which allows the gears to move in relation to each other under high loads that wouldn't affect the steel case. The case can be modified with a bushing that tightens up the fit and gives the same performance as the steel cases.

To add to that, I think the aluminum case can wear at that lower shaft and further increase how much the gears moving away from each other. And when the gears deflect the result can be breaking teeth off.

In addition, AJ/FormS has said that there are fewer splines on the OD gear and that gear can easily be broken under a hard shift to "4th".

I've never broken one myself, but I've never had what anyone would call a powerhouse in front of one either. Always been too poor to do much more than a bottom dollar rebuild and add a cam.
 

jos51700

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The issue with the aluminum case is the lower shaft is a loose fit in the case which allows the gears to move in relation to each other under high loads that wouldn't affect the steel case. The case can be modified with a bushing that tightens up the fit and gives the same performance as the steel cases.

To add to that, I think the aluminum case can wear at that lower shaft and further increase how much the gears moving away from each other. And when the gears deflect the result can be breaking teeth off.

In addition, AJ/FormS has said that there are fewer splines on the OD gear and that gear can easily be broken under a hard shift to "4th".

I've never broken one myself, but I've never had what anyone would call a powerhouse in front of one either. Always been too poor to do much more than a bottom dollar rebuild and add a cam.

I get all that. I guess I'm looking for first hand experience of what kills these gearboxes.

As in, "when MINE broke, I was....."
 

DionR

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I get all that. I guess I'm looking for first hand experience of what kills these gearboxes.

As in, "when MINE broke, I was....."

Gas price going up // Rethinking the new project car

Gas price going up // Rethinking the new project car

Any LowBuck but STRONG overdrive option?

Looks like I misunderstood and it isn't the number of splines but the number of teeth on the gear.

Looks like AJ/FormS has broken 3 of them and all of them were from stripping the teeth off the OD gear?
 

jos51700

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Gas price going up // Rethinking the new project car

Gas price going up // Rethinking the new project car

Any LowBuck but STRONG overdrive option?

Looks like I misunderstood and it isn't the number of splines but the number of teeth on the gear.

Looks like AJ/FormS has broken 3 of them and all of them were from stripping the teeth off the OD gear?

That's interesting that the flywheel ripped em out. @AJ/FormS I'm running an aluminum flywheel. I wonder if that would help the longevity of I chose to run this box
 

Josh owen

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I've got one of each.. one NON OD. One steel OD and one aluminum OD. Really wanted to use aluminum for weight wise but may use steel OD just for the cruising side of this. It's not a crazy small block 340 aluminum heads dual plane and 750 holley DP. Whiplash cam and 3.91 suregrip.
 

gzig5

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I get all that. I guess I'm looking for first hand experience of what kills these gearboxes.

As in, "when MINE broke, I was....."
Mainly shock in my opinion, like launching at high rpm on a strong motor with good grip. You are applying a ton of torque in a short time period (shock) and that will break parts. I'm sure a high HP engine could kill one eventually too even if you ease into it. On the other hand, I know a guy with a lot of racing experience with them that swears when they are properly built they will last. He has had them in B-bodies that carried the front tires at launch with no issues. The OD helps with the short gearing on the street.
 

Rat Bastid

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That's interesting that the flywheel ripped em out. @AJ/FormS I'm running an aluminum flywheel. I wonder if that would help the longevity of I chose to run this box


The clutch is what breaks transmissions. You have to have some way to control the application of the clutch. If not you’ll break it.
 

rumblefish360

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Shock from dumping the pedal
Clutch tamer… or
Excellent foot control
 

AJ/FormS

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As in, "when MINE broke, I was....."
1) one time, with deep 3.55s, I was banging thru the gears and in the excitement, I forgot which box was under the stick, and Zing od was history. see below.
2) one time, It was winter and I had my stock, low-compression 318 (allbeit with a TQ and the TTIs,) with a different od box, NOT acting crazy, but .... zing, od was gone.
3) one time, the 360 zinged off all the teeth of the input gear.
Now; there are TWO different tooth-counts of these boxes;
>one of them has a .71overdrive which it does with an 18tooth mainshaft gear. When the cluster engages this mini gear, it pretty much engages just one of those 18 teeth, atta time.
>The other has a .73overdrive, which IIRC has 21teeth, and has a bit more contact area.
NONE, I repeat, NONE of the gears between these two boxes will interchange, they have to be used as a set.
> that tooth-count difference is worth ~100rpm, so of course, I was trying desperately to use it. lol.
The 18 tooth gear, in my experience, cannot take much torque or abuse. The 21tooth seems to be a lil more robust.
As for the alloy box I was using at the time; I had a machine-shop machine out the front cluster pin-hole, and install a steel bushing, with a light press-fit to the pin. Just enough to not leak oil. BTW, The overdrive gear is AT THE BACK of the box, so any error on their part would NOT affect the od gear.

Currently I run a Commando gearset in a Passon Performance alloy box, with the GVod behind it. No more problems. In the beginning I had a bit of elusive to diagnose vibration, that I traced to THREE sources and fixed them one by one. The first was the cruising pinion-angle, the Second was the short driveshaft. The third was the Diaphragm clutch with it's centrifugal flyweights, the take-away here is to not try and cruise at too-low an rpm because the flyweights may not all park in the same place at the same time. There is no solution to this, even at 65=2240rpm. My best solution is to, once cruising, clutch it and blip the throttle. Sometimes it takes a few tries.

Here's the thing;
if you run a street gear like a 3.55, then 5500 in "third gear" will be about 124 mph, and it is hardy likely that you would ever power-shift into overdrive. AND, because of the H-pattern shifter, it is impossible to powershift from Second into "Fourth". So for most guys, that 23tooth gear is relatively safe.
And the other thing is this;
With 3.55s again, 65mph is ~4800 in 1.67ratio/Second. This is just past peak torque with "a bit of a cam".. Since this is the speed limit up here in Manitoba, it was all too easy for me to skip Direct/Third, and go straight into Fourth/overdrive. Well with a CF-II disc and a factory heavy-flywheel, and the rpm forced to drop to 2040, you HAVE TO WAIT FOR THE RPM TO COME DOWN! else the inertia in the flywheel will rip the teeth right off. :(
SO;
if you promise to be kind to overdrive, then you should be fine.

But did you catch that 65=4800 in that 1.67 ratio? That is about where the factory 318 cam makes peak power. So at 4800 you are a good 300 to 500 below the powerpeak of a typical street cam and a good 500 to 800 below it's shift rpm. So I donno why the heck you would run 3.55s.
To hit 65 at say 5500, on the backside of the power curve of a "bit of a cam" would require a road gear of 6.795, and 6.795/1.67=4.07, so the right gear to run, is gonna be about 4.10s for 65=5540 with 27" tires. And that make 65=2420 a very nice place to be. But when you hit redline in Second, do yourself a favor and shift into THIRD
NOT OVERDRIVE!
, lol.
Cuz when it goes ZING, you better have a rev-limiter.....

If you do Strip off a gear, clutch it, and STOP THE CAR!
You have no control of where those pieces are gonna go. If they end up between teeth of another ratio, they will take the rest of the box out. But before they do, they could lock-up the rear wheels, and if/when that happens at 65mph, NOTHING GOOD will come of it. Tow the car home and drop the trans. After a good clean out, you can still drive it as a 3-speed until your new gears come in. But I gotta tell ya, I highly recommend having a spare one in the garage.
 

rumblefish360

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Wait, how the heck do you come up with “if you run a street gear like a 3.55, then 5500 in "third gear" will be about 124 mph?”
What size tire is this. You assume a bit here huh?
Have you personally done this?
Same with all the other math

This is all gotta be KPH
 

AJ/FormS

68 Formua-S fastback clone 367/A833/GVod/3.55s
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The clutch is what breaks transmissions. You have to have some way to control the application of the clutch. If not you’ll break it.
and that is why after the first time it happened, I did the following.
1) I swapped out he CF-ll disc, in favor of a factory 340 disc. They don't last as long but they are much more gentle.
2) I reduced the clamping of the CF pressure plate by spacing it away from the flywheel. It slips a lil off idle, but when the flyweights come in, it's all good. This makes for very pleasant and relaxing drive-aways. Starting off, with 3.55s is more or less a "dump it and go" routine, almost right off idle.
3) Every time I get in the car, I remind myself; this transmission is a 3+1.
4) I practiced NOT shifting into Fourth, EVER, unless I was going on a cruise; 1-2-3 STOP!, lol.

In the end, I pulled it out.
 

rumblefish360

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Smart thinking not abuse the 4-OD gear.
3+1, I like it and see it that way as well.
 

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