200 Inline six 3spd to C4 swap

[JBrez]

Hey all,

My '72 Bronco is pretty much a daily driver. I am looking to swap the stock manual 3spd behind my 200 inline six with a c4. I was trying to do some research but I'm not finding much info for a six cylinder. Also, I was wondering if the gearing in the c4 would be better or worse then the stock 3 spd. It has the stock 4.10 gears in the rear. It cruises pretty good on the highway taching 3k rpm at 60mph.

Thanks,

Josh

 

[Viperwolf1]

Casadejohnson has done it. Look in his threads.

 

[blubuckaroo]

I'd say the three speed you've got is better suited for six cyl use than the C4.
The C4 has an extremely high 1st and 2nd gear.
There is a wide ratio planetary gear reduction kits for the C4 that would make it more appropriate. It would make a nice package, in my opinion.

Here are the tranny gear ratios we're talking about...

Manual Transmissions 1st 2nd 3rd
Bronco 3 spd (6 cyl) 3.41 1.86 1.00
Bronco 3 spd (8 cyl) 2.99 1.75 1.00

Automatic Transmission 1st 2nd 3rd
Bronco C4 2.46 1.46 1.00

 

[MPG_Bronco]

I'd say the three speed you've got is better suited for six cyl use than the C4.
The C4 has an extremely high 1st and 2nd gear.
There is a wide ratio planetary gear reduction kits for the C4 that would make it more appropriate. It would make a nice package, in my opinion.

Here are the tranny gear ratios we're talking about...

Manual Transmissions 1st 2nd 3rd
Bronco 3 spd (6 cyl) 3.41 1.86 1.00
Bronco 3 spd (8 cyl) 2.99 1.75 1.00

Automatic Transmission 1st 2nd 3rd
Bronco C4 2.46 1.46 1.00

you're forgetting the Torque Converter (TC)... 2.46 is when it's 'locked' 1:1 (engine Crank Shaft to Trans Shaft)... which we know c4's don't lock... but the slippage of the TC will act MUCH lower than what it REALLY is... if crusing at 3k rpm with manual EXPECT to be withing 300-500 MORE with auto... yup 3300 to 3500 rpm. it's just what it is...

now you can lower RPM by adding bigger tires, but remember, your take off will be much slower.

in newer trans (AOD AODE etc...) there is a TC that WILL lock once it hits the right RPM. IDK if these are transferable to C4's.

 

[JBrez]

Thanks for all of the responses!

Viperwolf, I checked out cascadejohnson's thread. A lot of good info. Seems like you are the man when it comes to the c4's.

MPG_Bronco, Thanks for the info! I have 31x10.50s now and I am not planning on going any bigger. I'll have to keep doing some homework. I don't mind the three speed...just wanted the wife to be able to drive it. She has no desire to learn the "three on the tree".

 

[Broncobowsher]

At 3000 RPM you are into the coupling phase of the convertor slippage with only 100-200 RPM slippage

 

[broncnaz]

Overall you wont see much difference between the 3sp and c4 just wont have to shift anymore. Take off may improve a little due to the torque converter. but 2nd and 3rd will be about the same.
You might want to do a few engine mods as autos take a little more power to turn and the 200 already lacks power.
For all the effort and modifications needed to put a c4 behind a 6cyl. I would really consider stepping up to a V8 and maybe a OD tranny.

 

[Viperwolf1]

Ford built millions of 170/C4 combos. Tell me some more why it can't work.

 

[JBrez]

Broncnaz- The previous owner did a mild performance rebuild on the 200...he used classicinlines.com stage 2 build as a guideline. The little 200 actually runs pretty darn good! He tricked it out with all the good stuff, but I also know there's no replacement for displacement.

 

[blubuckaroo]

Ford built millions of 170/C4 combos. Tell me some more why it can't work.

Oh sure, a C4 would work but the three speed that came in a six cylinder Bronco has a more appropriate 1st & 2nd gear.

Personally, I think a few lessons on manual shift driving would be much easier and more effective than swapping in an auto tranny.

 

[JBrez]

Oh sure, a C4 would work but the three speed that came in a six cylinder Bronco has a more appropriate 1st & 2nd gear.

Personally, I think a few lessons on manual shift driving would be much easier and more effective than swapping in an auto tranny.

HaHa....I'm considering that option!