Modern Drivetrain Swap into '65 Valiant

[AJ/FormS]

Hang on Scamper. If I understand you right, your car could 10 minutes or $100 bucks, from a new personality. You said

3.55s. Which is safer imo, but only accentuates the cars lack of performance. The trans will shift (in drive) at or below 2500 rpm so now instead of having the perfectly split gearset you described i have a package that will not pull until it’s in third gear but revs at 3000 while cruising at 65!

When you changed the rear, and the old one was NOT also 3.55s, then you have destroyed the relationship between the Governor and the Throttle pressure.
The governor pressure is directly linked to driveshaft rpm.
and Commands the shifts in "automatic mode" which is in drive.
In your case; lets say your previous gear ratio was 2.73s. Now with 3.55s, your Driveshaft rpm has risen by 3.55/2.73= Plus 30% !!
This causes all auto-shifts to come too early all the time. The only cure is to install a lighter-weight governor to reduce it's pressure.
But
Throttle pressure fights against governor pressure. So sometimes, you can increase the throttle pressure at the KD mechanism, to get back into the ballpark. I assume you have tried this, and did not receive satisfaction. This was the 10 minute shortcut.
Here comes the Hundreddollar fix;
Changing the governor out is gonna take a couple of hours but first, you need to get the right governor . This job is neither hard, nor complicated and requires no special tools. All it takes is time, and the part.
You can that part out of any transmission that was in a car that from the factory, had 3.55s, either 727, or 904. Or you can just call up somebody like A&A transmissions and for a bit of coin it will be in the mail to you. They can also hook you up with a new speed-O gear.
BTW, 727s and 904s can use the same governor parts.
After you get that installed, then you can fine tune the auto upshift speeds with Throttle pressure and Line pressure. This should be exciting to you, cuz in the end you will get exactly what you want, and it will be cheap.
As for the hiway rpm, there's nothing cheap about changing that!, lol.

In My Opinion, 3.55s are a great performance gear; I have been running them as my go-to gear since 1970 (no not the same ones,lol). But as you found out, they suck on the hiway.
In My Opinion, if you have to make significant hiway mileage, you HAVE to consider other options. A higher stall, more cylinder pressure, or a bigger engine would have solved your initial complaint, without the hiway rpm.

As to skidding out of control at speed; the posi/SureGrip will do that even easier than a peg-legger. So then; now that you have one, you will need to be even more careful on snow or ice or mud.
Happy HotRodding.

Governor Kits - A&A Transmissions

 

[ScamperTom]

Hang on Scamper. If I understand you right, your car could 10 minutes or $100 bucks, from a new personality. You said


When you changed the rear, and the old one was NOT also 3.55s, then you have destroyed the relationship between the Governor and the Throttle pressure.
The governor pressure is directly linked to driveshaft rpm.
and Commands the shifts in "automatic mode" which is in drive.
In your case; lets say your previous gear ratio was 2.73s. Now with 3.55s, your Driveshaft rpm has risen by 3.55/2.73= Plus 30% !!
This causes all auto-shifts to come too early all the time. The only cure is to install a lighter-weight governor to reduce it's pressure.
But
Throttle pressure fights against governor pressure. So sometimes, you can increase the throttle pressure at the KD mechanism, to get back into the ballpark. I assume you have tried this, and did not receive satisfaction. This was the 10 minute shortcut.
Here comes the Hundreddollar fix;
Changing the governor out is gonna take a couple of hours but first, you need to get the right governor . This job is neither hard, nor complicated and requires no special tools. All it takes is time, and the part.
You can that part out of any transmission that was in a car that from the factory, had 3.55s, either 727, or 904. Or you can just call up somebody like A&A transmissions and for a bit of coin it will be in the mail to you. They can also hook you up with a new speed-O gear.
BTW, 727s and 904s can use the same governor parts.
After you get that installed, then you can fine tune the auto upshift speeds with Throttle pressure and Line pressure. This should be exciting to you, cuz in the end you will get exactly what you want, and it will be cheap.
As for the hiway rpm, there's nothing cheap about changing that!, lol.

In My Opinion, 3.55s are a great performance gear; I have been running them as my go-to gear since 1970 (no not the same ones,lol). But as you found out, they suck on the hiway.
In My Opinion, if you have to make significant hiway mileage, you HAVE to consider other options. A higher stall, more cylinder pressure, or a bigger engine would have solved your initial complaint, without the hiway rpm.

As to skidding out of control at speed; the posi/SureGrip will do that even easier than a peg-legger. So then; now that you have one, you will need to be even more careful on snow or ice or mud.
Happy HotRodding.

Governor Kits - A&A Transmissions

Lots of info, thanks! Years of searching the forum and I still don’t know this.

I don’t fully understand, however. Driveshaft speed doesn’t change with respect to engine speed and throttle, since the trans ratios haven’t been changed. I would imagine that as long as I’m full throttle the governor would sense the engine speed and shift at the appropriate moment no matter how fast the wheels turn. Does the governor instead also somehow work in relation to car speed? I did adjust the kickdown linkage and I think it’s how it’s supposed to be.

As to losing traction, I don’t think you’re entirely right in this case about the posi being worse. My motor isn’t exactly a torque monster and having to break two wheels free is undoubtedly harder than just one. But more importantly, a skid is way easier to control when the behavior of the tires is predictable. At least you can control the amount and direction of wheelspin when both tires are loose.

 

[AJ/FormS]

Driveshaft speed doesn’t change with respect to engine speed and throttle, since the trans ratios haven’t been changed.

If you changed the rear gear ratio, then the rpmat any given roadspeed has changed by the percentage difference between the gears. You won't notice a small change on the speed-O (which is calibrated for the out=going gears, BUT
You most certainly will see it on the tach as a similar percentage change in rpm ...... for the corrected roadspeed.
Here's what I mean:
going from 3.23s to 3.55s, with no other changes;
With 3.23s, 65=2614rpm with 27" tires.
With 3.55s, 65=2873rpm still with 27s; and both are at zerp-slip.
This is a percent increase in driveshaft speed of 3.55/3.23= plus 9.907%
Your speed -O will now be in error by that 9.907%, reading higher because the driveshaft speed is higher. You may not find this out until you get a speeding ticket.
But; your tach will tell the tale. If you drive the 3.55s at 2614 rpm as you did the 3.23s, then you will be driving at 9.907% slower, or 6.44 mph slower = 60.8 mph.
Your Speed-O only has to be corrected if you can't do the math-correction in your head, or if someone else is gonna drive it.

This driveshaft rpm increase causes your governor flyweight to fly out at a quicker rate, which increases it's pressure, which then over-rides the line pressure+throttle pressure, and this action causes your shifts to occur earlier than before.
You can change your throttle-pressure at the KD mechanism, but if when it is maxed out, your auto upshifts are still too early, then the only other thing you can do is go into the governor and reduce the pressure by delaying the flyweight by making it lighter.

Now, if the auto-upshifts have become too high after the governor swap, then you have to go back to the KD mech and reduce the Throttle Pressure. If you cannot bring the auto upshift speed down far enough to make you happy, then you have installed a too-light governor and will have to swap it out for a slightly heavier one. They call this; Hot-Rodding, lol

You can get around all this Hot-Rodding, by simply manually downshifting the trans, and holding it in gear, until you think the engine is past it's prime, or until it has exploded, whichever comes first. There, I hope that is a lil more clear.

 

[AJ/FormS]

Does the governor instead also somehow work in relation to car speed?

The governor has NO IDEA about engine rpm;
The governor has no idea about the roadspeed;
The governor only knows driveshaft rpm, and only responds to increasing rpm , by increasing it's Shift-Command Pressure.

Anytime a rear gear ratio is changed, the governor will need to be re-educated. And the Speed-O will need a new drive-gear.

 

[AJ/FormS]

As to losing traction, I don’t think you’re entirely right in this case about the posi being worse. My motor isn’t exactly a torque monster and having to break two wheels free is undoubtedly harder than just one. But more importantly, a skid is way easier to control when the behavior of the tires is predictable. At least you can control the amount and direction of wheelspin when both tires are loose.

I think you misunderstood my meaning.
With an open diff, it is almost impossible to initiate a sideways skid, unless there is close to zero traction. This is because at least one wheel back there is always fully connected to the road. This is why you cannot make your one-legger fishtail, unless you get violent with the steering wheel..
However, with a Suregrip, both rear tires want to turn at the same rpm. So if you get into a skid, adding power will make it worse, and lifting off the throttle MAY make it worse. If you want to recover from the back-end stepping out, your only option is to restore the tires to the exact right roadspeed, so the rubber can do it's job.
A very long time ago, I figured out that the best way to do this is to disconnect the tires from the engine, by clutching it, or popping the auto-stick into neutral. If the road is icy, wet, or somehow slick, once a skid starts, you only have milliseconds to react, so you have to be prepared beforehand; this action has to be instinct. And that my friend, takes practice; lots and lots of practice. If the back-end steps out more than a few degrees and loses grip, it is coming around to pass you and there is capital ZERO that you can do about it. You only have milliseconds to restore grip, or pray.
Friend, this is why my car has 295s on it. I was tired of losing grip and spinning out, altho I must admit, I was pretty good at going off-road ....... backwards, lol. These 295s have a lot of sideways rubber, so when I sense an impending spin-out, I just disconnect the power and let the tires save me. I can't tell you how often this trick has saved the day. Nor can I tell you how many passengers have had their necks massaged by it, and they no longer beg for rides. lol.
A SureGrip is only good for two things, namely;
1) straight line torque-splitting for traction under power, and
2) show-off drifting
both of these are best done on a clean, dry, level, hard, and flat surface; I think that is called "prepped", lol.

 

[ScamperTom]

This driveshaft rpm increase causes your governor flyweight to fly out at a quicker rate, which increases it's pressure, which then over-rides the line pressure+throttle pressure, and this action causes your shifts to occur earlier than before.
You can change your throttle-pressure at the KD mechanism, but if when it is maxed out, your auto upshifts are still too early, then the only other thing you can do is go into the governor and reduce the pressure by delaying the flyweight by making it lighter.

I understand how the interaction between the diff gearset and the trans gear ratios will change rpm at a given speed. Really i was asking about the mechanics of it. The sentence in bold seems important. A steeper rear will increase engine rpm at a faster rate. Is it this change in rate what actually causes the earlier shift? Because really when I’m matted I don’t care about what speed i shift at, only rpm, so that i can take full advantage of the motor. So even tho a different rear will have a different speed at a certain engine rpm, I’m still not positive how the governor (which you said is ONLY rpm dependent) will actually end up shifting at a different rpm. (Whether it shifts at a different speed is irrelevant in this particular case.)

I’ve helped blow a few motors, but I’d like to avoid it if possible, haha.

I think you misunderstood my meaning.
With an open diff, it is almost impossible to initiate a sideways skid, unless there is close to zero traction. This is because at least one wheel back there is always fully connected to the road. This is why you cannot make your one-legger fishtail, unless you get violent with the steering wheel..
However, with a Suregrip, both rear tires want to turn at the same rpm. So if you get into a skid, adding power will make it worse, and lifting off the throttle MAY make it worse. If you want to recover from the back-end stepping out, your only option is to restore the tires to the exact right roadspeed, so the rubber can do it's job.
A very long time ago, I figured out that the best way to do this is to disconnect the tires from the engine, by clutching it, or popping the auto-stick into neutral. If the road is icy, wet, or somehow slick, once a skid starts, you only have milliseconds to react, so you have to be prepared beforehand; this action has to be instinct. And that my friend, takes practice; lots and lots of practice. If the back-end steps out more than a few degrees and loses grip, it is coming around to pass you and there is capital ZERO that you can do about it. You only have milliseconds to restore grip, or pray.
Friend, this is why my car has 295s on it. I was tired of losing grip and spinning out, altho I must admit, I was pretty good at going off-road ....... backwards, lol. These 295s have a lot of sideways rubber, so when I sense an impending spin-out, I just disconnect the power and let the tires save me. I can't tell you how often this trick has saved the day. Nor can I tell you how many passengers have had their necks massaged by it, and they no longer beg for rides. lol.
A SureGrip is only good for two things, namely;
1) straight line torque-splitting for traction under power, and
2) show-off drifting
both of these are best done on a clean, dry, level, hard, and flat surface; I think that is called "prepped", lol.

I think in my case the 5” wheels may have had something to do with it… you’re absolutely right that more rubber usually makes for safer driving. But I’ve learned from the track that the most controlled way to recover from a slide is to slowly reintroduce traction which is easier with a posi because neither wheel will unexpectedly grip. With a peg-leg it can be hard to be sure which wheel will have traction, which makes controlling a slide by modulating throttle much more difficult. Certainly for guys like me who had all the wrong instincts anyway! Lifting off completely, overcorrecting on a slippery road! I was lucky traffic wasn’t close. Anyway maybe a driver mod was more important than the new rear, but I’ll still take it.

 

[dart4forte]

There’s a guy that lives north of Phoenix that owns my old 64 Dart vert. Last time I saw the car which was on FB he put a 5.7 in it. I’d sur like to get the old drive train out of that car.

 

[ScamperTom]

There’s a guy that lives north of Phoenix that owns my old 64 Dart vert. Last time I saw the car which was on FB he put a 5.7 in it. I’d sur like to get the old drive train out of that car.

View attachment 1715886994

Good looking car without the bumper

 

[ScamperTom]

Well the project is definitely turning into a lot more work than i had anticipated. Still, I’ve made some good progress! Made some budget choices with the frame design that I’m not completely sold on, but the new frame is in and square.

I was able to toss in a mockup motor and trans and fabricate a new crossmember.

i realized that I’ll have to inset the firewall about 3”, which I was initially hoping to avoid. Still, that shouldn’t be a problem. The hood torsion bars do clear the motor, and I would rather keep them than go to struts. The most difficult part is likely to be rebuilding a new cowl and fresh air system, since I had to completely cut away the old one as it was just too rusty to trust.

I also built a basic unsupported 6 pt cage to help with rollover protection and to stiffen up the chassis. Because space at the shop is at a premium, I had to do all the fab work in sections, so unfortunately the new completed chassis is about 1/4” out of square. The new suspension should be perfectly capable of handling that, however, so I’m pretty pleased with how it’s turning out.

Next I’ll have to finalize the cowl and firewall, and widen the rear tunnel to allow the car to sit at its new ride height, which will probably comfortably be 3” lower than stock, since I no longer have to worry about header clearance or front tire scrubbing.

 

[fig]

A lot of work, it will be worth it when you are done.

 

[64_Barracuda]

Tom,
Any new updates? I have a 63 Dart Wagon, I am thinking of the V6 upgrade, wondering how your project is coming. I have good floors and sheet metal, looking to not hack the car to heck. Any pictures, help or tips would be great.

 

[ScamperTom]

Tom,
Any new updates? I have a 63 Dart Wagon, I am thinking of the V6 upgrade, wondering how your project is coming. I have good floors and sheet metal, looking to not hack the car to heck. Any pictures, help or tips would be great.

I hadn't touched it in about six months until last week. Just been busy with other things. I built the firewall and cowl, but no other progress so far. Six months is plenty of time to regret your design choices, haha!

If your car has good metal I would keep as much of it as you can! No sense creating unnecessary work. What V6 are you thinking of, the 3.6 Pentastar? There's a great thread on that swap you can look up.

 

[64_Barracuda]

Yeah I think the 3.6, the 63 has the wiper motor pop out on the fire wall, so I figure a V6 I should be able to stay away from the fire wall. It's a wagon, I just need performance and reliability

 

[ScamperTom]

You're not guaranteed fitment because it's missing a couple cylinders. The biggest issue is likely to be fitting the drag link around the oil pan. Without fabricating a new link, that will probably determine where you'll set the motor.

 

[GGs66GT]

The trans will determine where the back of the engine is in relation to the firewall , providing the trans is mounted in the stock location.

 

[ScamperTom]

Finally getting the energy to finish the interior sheet metal work. Really kicking myself for trying to save time by keeping the factory crossmember. I lost a couple inches of ground clearance and caused a lot of headaches for myself. Still, just want to move forward with the project. It is a poverty build after all; much more invested in labor than parts.

I still have to finish the floors and then I can revisit the engine bay and fix a couple of crucial rust spots. I really need to start painting as I go, outdoor storage has not been friendly…

 

[ScamperTom]

I got after the interior fabrication a bit more and was able to finish the floors.

Then I seam sealed the bottom of the car and sprayed epoxy primer on the interior raw steel.

I patched a few exterior rust holes that will let water inside and cause future problems. I'm not too concerned with the rust generally, just the spots that will cause issues with what I've built.

I had no idea there was so much lead filler on this car! Found out the hard way that lead doesn't weld to steel, lol. I don't have the time to remove it and weld in a full patch so the steel here will just have to act as the base for my bondo.

I also tagged the cage into the A-pillars and added a flange to allow me to glue the windshield in instead of using the OEM gasket.

Now "all" that's left is to fix a few more rust holes in tricky spots and finalize the engine bay sheet metal work!

Wish me luck!

 

[ScamperTom]

I just wanted to show how I modified the Valiant's steering column to fit the Miata pedal assembly and steering linkage. Of everything I've done to the car, this was by far the most interesting bit of fab work.

First I disassembled both the Valiant's and the Miata steering columns. Then I cut both shafts and columns to keep the steering wheel close to the OEM location.

I welded the shafts together with a sleeve and welded the Mopar column onto the Miata's base where it bolts to the firewall.

Using parts from both columns allowed me to keep the Plymouth upper column bearing and steering wheel assembly stock, while still keeping the stock bearing and bolt-in assembly from the Miata. The distance from the firewall to the steering rack itself is slightly different from the Mazda, so I'll likely have to extend the lower shaft with a sleeve in the same way.

I still have to fully brace the pedal assembly and perhaps modify the pedal positions, but overall I'm pretty happy with how it turned out! The good thing about using the Miata parts is that lots of kits exist to bolt in different motors to that subframe, which should all be pretty much plug-and-play should I choose to go that route in the future.

 

[mopowers]

Nice!! That's a TON of work. Nicely done.

 

[JDMopar]

Tom....there's some 63-66 A pillars for sale here. I'll tag you in the ad so you can see if they will help you.