66 Newport T56 Swap

[Ben Herman]

1st isn't any taller than an NP833 factory 4 speed. 2.66 was an 833 1st gear ratio and the 2.97 is pretty close to the 3.09 ratio for /6 and OD 833s.

Kevin

I did some looking and couldn't find any proof anything was ever a 2.76 and a 4 speed. If that's the case I ought to be fine. Its certainly going to be a different world from my Dodge that its the governor at 4mph in low 1st.

 

[Dads300]

I don’t think you’ll have any issue with clutches, the first gear is similar to an 833 and plenty of guys have run 2.76 gears in 4 speed cars over the last 50 years without issue. A big engine with a heavy flywheel will drive away fine without needing to fry the clutch, so long as you know how to drive a manual correctly.

I think a Dana 60 would be counter to you efficiency goals. Everything about an 8 3/4” is lighter which would rob less power. You aren’t going to be hard launching or power shifting this thing if you want economy, so I would personally skip the giant diff.

I’m interested to see how it works for you, so be sure to update

Travis..

 

[fury fan]

I'm not telling you what to do, or not to do, just want to expand on something others have mentioned.

Fuel economy and fuel efficiency are NOT the same, and lugging an engine (especially one with old-school cylinder heads) does NOT usually lead to good MPG.
Many engines (at least those without adjustable valve timing, swirl-and-tumble cylinder heads, active intake manifolds, ECU-controlled ign timing, etc) want to have some RPM in order to have intake air velocity that leads to good combustion.
So putting an old-school engine with the drivetrain gearing of a modern car (remember to calc with tire dia also) isn't guaranteed to give the same results as what the factory engineers came up with.

T56 gear ratios for a Viper seem to be (2.66, 1.78, 1.3, 1.00, 0.84, 0.74) - actually not as bad as I expected for 6th.

So, axle gears with 6th OD -
2.76 * .74 = 2.04
3.23 * .74 = 2.39
3.55 * .74 = 2.62
3.73 * .74 = 2.76
3.91 * .74 = 2.89

Lowest axle ratios I have seen from Mopar is 2.20, and I can tell you that is a terrible ratio for anything other than a factory-built malaise-era car.
(80 Diplomat, 318-2 barrel, 904 trans with lockup TC - a very consistent 20mpg highway)

Also, what would be your baseline MPG for a 383 Newport on level ground with 2.76? You should exceed that by eliminating the TC slippage and losses in the AT.
But - how much can you realistically gain - and is it worth it?
How much can you improve MPG with a heavier car, larger engine, less aerodymanics? (vs my Diplomat example, I'm not saying the Diplomat was optimized, it's just a data point to compare)
I would be very surprised if any bigblock C-body, even with the optimum drivetrain combination, could exceed 25 mpg at 60 mph on level ground.

I'm not really interested in burning rubber or stoplight racing. I am interested in how far I can stretch 25 gallons of gas across Kansas.

I doubt you will get good MPG at 60mph with the 2.04.
You might with the 2.39 IF you can drive with a very soft/deliberate foot AND MPG feedback. And your target speed will be important.
I've had a few late 80s cars with MPG readout and can tell you that if you are lugging the engine it is VERY easy to eat into your MPG with poor foot-control on the throttle. You can absent-mindedly give it the slightest increase in throttle with very little results in speed because the drivetrain responds so poorly.

If you are using cruise control, I can assure you that you will get worse MPG the lower that OTGR is. To get max MPG your roadspeed must vary somewhat - you need to slow down a little (to hold throttle) while cresting hills (when possible) and then pick up a few mph on the way down. This can be an annoyance to other drivers, though.

You should also research the factors that reduce MPG to make sure you're hitting the right ones - road speed, aerodynamic drag, weight, rolling resistance (tire tread design, tire width, all your vehicle bearings) also play a role besides engine rpm.

My recommendation:
If you plan to drive 55-60mph across Kansas, 3.55 'safer' choice, maybe 3.23 might be OK.
If you plan on driving 70+, you need more torque to push the wind, so look to 3.73 or 3.91.

 

[fury fan]

Read this:
https://www.cummins.com/sites/default/files/cummins_secrets_of_better_fuel_economy.pdf

 

[Ben Herman]

I'm not telling you what to do, or not to do, just want to expand on something others have mentioned.

Fuel economy and fuel efficiency are NOT the same, and lugging an engine (especially one with old-school cylinder heads) does NOT usually lead to good MPG.
Many engines (at least those without adjustable valve timing, swirl-and-tumble cylinder heads, active intake manifolds, ECU-controlled ign timing, etc) want to have some RPM in order to have intake air velocity that leads to good combustion.
So putting an old-school engine with the drivetrain gearing of a modern car (remember to calc with tire dia also) isn't guaranteed to give the same results as what the factory engineers came up with.

T56 gear ratios for a Viper seem to be (2.66, 1.78, 1.3, 1.00, 0.84, 0.74) - actually not as bad as I expected for 6th.

So, axle gears with 6th OD -
2.76 * .74 = 2.04
3.23 * .74 = 2.39
3.55 * .74 = 2.62
3.73 * .74 = 2.76
3.91 * .74 = 2.89

Lowest axle ratios I have seen from Mopar is 2.20, and I can tell you that is a terrible ratio for anything other than a factory-built malaise-era car.
(80 Diplomat, 318-2 barrel, 904 trans with lockup TC - a very consistent 20mpg highway)

Also, what would be your baseline MPG for a 383 Newport on level ground with 2.76? You should exceed that by eliminating the TC slippage and losses in the AT.
But - how much can you realistically gain - and is it worth it?
How much can you improve MPG with a heavier car, larger engine, less aerodymanics? (vs my Diplomat example, I'm not saying the Diplomat was optimized, it's just a data point to compare)
I would be very surprised if any bigblock C-body, even with the optimum drivetrain combination, could exceed 25 mpg at 60 mph on level ground.


I doubt you will get good MPG at 60mph with the 2.04.
You might with the 2.39 IF you can drive with a very soft/deliberate foot AND MPG feedback. And your target speed will be important.
I've had a few late 80s cars with MPG readout and can tell you that if you are lugging the engine it is VERY easy to eat into your MPG with poor foot-control on the throttle. You can absent-mindedly give it the slightest increase in throttle with very little results in speed because the drivetrain responds so poorly.

If you are using cruise control, I can assure you that you will get worse MPG the lower that OTGR is. To get max MPG your roadspeed must vary somewhat - you need to slow down a little (to hold throttle) while cresting hills (when possible) and then pick up a few mph on the way down. This can be an annoyance to other drivers, though.

You should also research the factors that reduce MPG to make sure you're hitting the right ones - road speed, aerodynamic drag, weight, rolling resistance (tire tread design, tire width, all your vehicle bearings) also play a role besides engine rpm.

My recommendation:
If you plan to drive 55-60mph across Kansas, 3.55 'safer' choice, maybe 3.23 might be OK.
If you plan on driving 70+, you need more torque to push the wind, so look to 3.73 or 3.91.

6th on a Viper T56 is .5, not .74. I have no interest in how it will do at 60 or at 70. I've crossed Kansas at 4300 rpm before and don't care to do it again. Feel free to do the math at what speed that puts me at with 1:1 and a 2.76. A 3,23 gear is more likely what I'll end up with when its time to swap. I already have ecu controlled timing (FiTech) and the 440 will have better heads and cam when it gets put in. I aware that to absolutely maximise mpg I should slow down. I should probably swap it for a 4cyl as well or electric. Obviously the goal is to do as well as I can with a 440 and the speed I want.

 

[Ben Herman]

I don’t think you’ll have any issue with clutches, the first gear is similar to an 833 and plenty of guys have run 2.76 gears in 4 speed cars over the last 50 years without issue. A big engine with a heavy flywheel will drive away fine without needing to fry the clutch, so long as you know how to drive a manual correctly.

I think a Dana 60 would be counter to you efficiency goals. Everything about an 8 3/4” is lighter which would rob less power. You aren’t going to be hard launching or power shifting this thing if you want economy, so I would personally skip the giant diff.

I’m interested to see how it works for you, so be sure to update

Travis..

That seems like solid logic. Based on what I've seen here it seems like the Dana60 may not be the best choice for me. I've fallen for the "car show" and "hot rod" solutions before and been burned for it. Nearly every comment here can be used as an example. I'll be sure to take lots of pictures and post updates as it goes. I'm hoping to get the parts together this spring and start cutting. If all goes well I should have results by this summer.

 

[NitrousTuner1]

Unless you live in BFE & have miles & miles to cruise @ 130mph I'd definitely change that rear gear as you'll be missing 1 of the huge advantages of doing a T-56 swap....
And unless you've become use to shifting a Tremec versus a old school 4 speed DEFINITELY swap out shifter!! NOT just for the shorter throw advantages But for the billet stops you want.... These trannys can & will get damaged Easily by shifting with any force. So you want a aftermarket shifter base that has the travel stops to keep yourself from bending & or breaking the internal shift forks....
Lastly what rear tire you running? As those car's tuck a nice 275/60 easily even with skirts
#realcarshave3pedals

 

[Ben Herman]

Unless you live in BFE & have miles & miles to cruise @ 130mph I'd definitely change that rear gear as you'll be missing 1 of the huge advantages of doing a T-56 swap....
And unless you've become use to shifting a Tremec versus a old school 4 speed DEFINITELY swap out shifter!! NOT just for the shorter throw advantages But for the billet stops you want.... These trannys can & will get damaged Easily by shifting with any force. So you want a aftermarket shifter base that has the travel stops to keep yourself from bending & or breaking the internal shift forks....
Lastly what rear tire you running? As those car's tuck a nice 275/60 easily even with skirts
#realcarshave3pedals

A shifter with stops seems to be a requirement from what I've heard. With all the extra leverage of the long shifter I'd probably break something quick. My experience is almost entirely 4 speed truck transmissions and a bit of time with a Spicer with 30' of linkage between the trans and shifter. I was originallly planning on putting a NP435 or a similar OD trans in the Chrysler before I was told about the T56.

 

[Michael E Mason]

Swapping gears in the 8.75 would get me the gears I don't want and still no disc brakes. I won't be swapping away from 2.76 unless I am already swapping to a Dana60 because the Dana60 doesn't have any gear taller than a 3.23. If a Dana60 2.76 was available I'd get that.

I'm really not here to argue if my gearing is a good or bad idea. I can go to any car club meet to listen to people tell me I'm "doing it wrong" building something with a different goal than the usual. They usually quiet down after they watch me hit 115 in 2nd.

I want to see what I'm going to have to cut and see what clutch, flywheel, and bell housings people have used and how they like them.

I put front and rear discs on my 66 Newport Convertible. Let me know if you want pics and the name of the company that makes the kit.

 

[Ben Herman]

I put front and rear discs on my 66 Newport Convertible. Let me know if you want pics and the name of the company that makes the kit.

I'm definitely interested in pictures and how yours went and your opinions on it. I got a SSBC kit for the front and had a pretty terrible experience all around. Parts of the kit that didn't fit together, it was advertised as compatible with the factory booster, the rotors were warped out of the box, the pads seemed to be made of butter, and support was lacking.

 

[Michael E Mason]

Here are pictures of the front and rear disc setups. I had to put a spacers on the front and rear to clear the calipers because of drum style rims. I wanted to keep my original 14" rims and hubcaps and this setup worked perfectly! I had to adjust the side to side play on the 8 3/4" rear axles because I had the axles out putting new bearings on. Once I got them adjusted correctly, the brakes work great. The pads and calipers are 64-66 Ford Mustang units on the front. The kits for the front and rear came from Summit Racing and here are the details -

LEB-FC2003-8405 Disc Brake Kit, Front Conversion, Power Assist, Solid Surface Rotors, Cast Iron Calipers, Zinc Plated, 5 x 4.50 in. Bolt Pattern, Kit (Mfr. #: FC2003-8405)​ Ready to Ship Ground​ $1,150.99​ 1​ $1,150.99​

TSB-A155BK Disc Brake Kit, Drum to Disc Conversion, Rear, Solid Surface, Chrysler, Dodge, Plymouth, Kit (Mfr. #: A155BK)​ Ready to Ship Ground​ $777.10​ 1​ $777.10​

The best part is this kit allows you to use your existing spindles, no need to change to later disc style spindles. The only issue was with the brake pedal arm that attached to the booster. They sent three different lengths but none were correct. I had to modify the shortest one but I finally got it to work. Here is how it looks after the conversion with the spacers on. I also replaced all the emergency brake cables and they clicked into place perfectly on the calipers.

 

[Ben Herman]

Here are pictures of the front and rear disc setups. I had to put a spacers on the front and rear to clear the calipers because of drum style rims. I wanted to keep my original 14" rims and hubcaps and this setup worked perfectly! I had to adjust the side to side play on the 8 3/4" rear axles because I had the axles out putting new bearings on. Once I got them adjusted correctly, the brakes work great. The pads and calipers are 64-66 Ford Mustang units on the front. The kits for the front and rear came from Summit Racing and here are the details -

View attachment 581482​ LEB-FC2003-8405 Disc Brake Kit, Front Conversion, Power Assist, Solid Surface Rotors, Cast Iron Calipers, Zinc Plated, 5 x 4.50 in. Bolt Pattern, Kit (Mfr. #: FC2003-8405)​ Ready to Ship Ground​ $1,150.99​ 1​ $1,150.99​

View attachment 581483​ TSB-A155BK Disc Brake Kit, Drum to Disc Conversion, Rear, Solid Surface, Chrysler, Dodge, Plymouth, Kit (Mfr. #: A155BK)​ Ready to Ship Ground​ $777.10​ 1​ $777.10​

The best part is this kit allows you to use your existing spindles, no need to change to later disc style spindles. The only issue was with the brake pedal arm that attached to the booster. They sent three different lengths but none were correct. I had to modify the shortest one but I finally got it to work. Here is how it looks after the conversion with the spacers on. I also replaced all the emergency brake cables and they clicked into place perfectly on the calipers. View attachment 581481

View attachment 581479

View attachment 581480

That front kit is very similar to the one I got and includes the same calipers. I've heard lots of people say they had good luck with SSBC so maybe I'm the odd one out. I also had to modify the brake lever arm to get the correct length. I also went for the 14" wheel kit and regret it now. I switched to 15s a while later so I could actually buy decent affordable tires for it. At the time I was averaging 20k per year on the car so I didn't want to buy reproduction oem stuff.

 

[Unix]

Awesome. Didn't know there was a conversion kit for the rear drums. This is now on top of my shopping list for my 71 Newport!