stock 3 speed vs. c4

[rockinrich]

Hey guys,i have a 3 speed right now,besides being an auto is there any other benefits to going from a 3 speed manual to a c4 auto?I know it costs more to switch over to auto,but there is one possibly with 70,000 miles on it for 475,and whatever it costs to ship from colorado to california,which might kill me,is that a fair price? with whatever else parts i'd need am i still better off going with an ax15 moneywise?Thanks in advance!p.s. he also said his reverse gear failed on him if that helps.

 

[Broncobowsher]

Hope it comes with the transfer case adaptor. Lot of little things that go into an automatic swap that can really add up. Dipstick and tube, shifter and linkage, cooler lines and some sort of cooling, etc. The value of that buy would highly depend on how complete the transmission is. And budget a rebuild since they stated it has failed.

Depending on the tire and gearing you are running now things can get interesting. The manual is more tolerant of too tall of a tire for the gearing, it just drives a bit doggy. Try running 33" tires and 3.50 gears with a C4 and you will just burn it up as you will always be up against the convertor.

AX15 adds another twist, overdrive. You may have to regear the axles to make the overdrive usable.

 

[rockinrich]

thanks bud,on a 74 bronco what gears would come stock on it? Also i plan on going with 33's but the c4 compared to my 3 speed the only thing i'm gaining is not having to shift correct? they are virtually the same?

 

[Broncobowsher]

You will have to check what you have. The V8 had two different gear ratios. 3.50 and the optional 4.11s. There is a tag in the glovebox that has axle codes on it, but after 45+ years that only tells you what it was built with and not what has happened in the years since then. There is a tech article on the left of the page that tells you how to check it with a piece of string and a little tape, takes out the error people get when trying to do it by jacking a tire in the air and spinning it.

Both the stock 3-speed and the C4 have the same top gear (1:1 ratio). The C4 will cruise with a little more RPM due to converter slip. The 3-speed actually has a little lower first gear (2.99:1) over the C4 (2.46:1) so you have less engine braking, but you do gain a little from a dead stop since the convertor will multiply torque. But that multiplication quickly drops as you start moving.

 

[blubuckaroo]

If you can find a take-off from someone who has converted their Bronco to manual, you could get all the stuff needed, including the steering column. That's how I sold mine when I converted to manual. The guy pretty much got a C4 conversion kit including all the fasteners. He had his together and running in less than a week.

I'd plan on a rebuild on the C4 before installation.
My C4 was rebuilt twice in the 300K miles I had it. It's very inexpensive to rebuild since it doesn't have overdrive or locking torque converter.

With either of the conversions you're considering, you're going to want lower than the standard 3.50 gears.
BTW, if yours was originally a six cylinder car, it would have come with either 4.11 or the optional 4.56 gears.
Fingers crossed!

 

[DirtDonk]

I say that's $400 too much for a transmission that has already failed, needs to be shipped, and may actually have 170,000 or even 270,000 miles on it. Granted, not many Broncos can claim over 200k miles, but by now I bet most Broncos have well over 100k on the odometer but you'd never know it since it rolls around to zero at that 100k mark.

Usually low mileage claims from any Bronco, or Bronco part seller are exaggerated (can't verify), unknown because that's just what the person they bought it from said, or out and out lies by the seller.

Are Bronco C4's getting that rare now? Not sure what else the pan-fill 4wd versions came in, but seems like they used to be relatively easy to find. Maybe the price has gone up just for "Bronco" versions because of the popularity and pricing of the vehicles?

I don't know, but that still seems like an awful lot to gamble on an unknown and an out-of-state shipper.

Paul

 

[Broncobowsher]

Paul,

That is why I put the qualifier of how complete it is. You are right, if it is only the C4 that is a complete rip off. But if it is a complete kit, I think it is a decent deal. All that little stuff adds up. So it needs a rebuild, you have your local rebuilder do it and if there are issues it is your guy and local. As compared to who know who's rebuild from across the country without a warranty.

The big question really is how much is included with the transmission?

 

[Viperwolf1]

Not sure what else the pan-fill 4wd versions came in, but seems like they used to be relatively easy to find.

Nothing else. The Bronco had the only factory 4x4 C4 made. There were 4x4 C5s in rangers/B2s but they were very different.

 

[rockinrich]

You will have to check what you have. The V8 had two different gear ratios. 3.50 and the optional 4.11s. There is a tag in the glovebox that has axle codes on it, but after 45+ years that only tells you what it was built with and not what has happened in the years since then. There is a tech article on the left of the page that tells you how to check it with a piece of string and a little tape, takes out the error people get when trying to do it by jacking a tire in the air and spinning it.

Both the stock 3-speed and the C4 have the same top gear (1:1 ratio). The C4 will cruise with a little more RPM due to converter slip. The 3-speed actually has a little lower first gear (2.99:1) over the C4 (2.46:1) so you have less engine braking, but you do gain a little from a dead stop since the convertor will multiply torque. But that multiplication quickly drops as you start moving.

Thank you for the info bud,i'm sure whatever gears ford put in are still there as it is bone stock,i'll attach a pic maybe you can tell me about the gears,thank you for the help!

 

[rockinrich]

If you can find a take-off from someone who has converted their Bronco to manual, you could get all the stuff needed, including the steering column. That's how I sold mine when I converted to manual. The guy pretty much got a C4 conversion kit including all the fasteners. He had his together and running in less than a week.

I'd plan on a rebuild on the C4 before installation.
My C4 was rebuilt twice in the 300K miles I had it. It's very inexpensive to rebuild since it doesn't have overdrive or locking torque converter.

With either of the conversions you're considering, you're going to want lower than the standard 3.50 gears.
BTW, if yours was originally a six cylinder car, it would have come with either 4.11 or the optional 4.56 gears.
Fingers crossed!

I appreciate your help,hate to dissapoint but it's a 302 v8 and it's bone stock so i'm assuming it has the 3.50 gears but look at the pic i put up and let me know your thoughts,thanks!

 

[Broncobowsher]

IF I decoded it right, B9 is 3.50 gears with the factory limited slip. Pretty common axle.
It won't be happy with 33" tires. Those are freeway gears for a Bronco.

 

[rockinrich]

I say that's $400 too much for a transmission that has already failed, needs to be shipped, and may actually have 170,000 or even 270,000 miles on it. Granted, not many Broncos can claim over 200k miles, but by now I bet most Broncos have well over 100k on the odometer but you'd never know it since it rolls around to zero at that 100k mark.

Usually low mileage claims from any Bronco, or Bronco part seller are exaggerated (can't verify), unknown because that's just what the person they bought it from said, or out and out lies by the seller.

Are Bronco C4's getting that rare now? Not sure what else the pan-fill 4wd versions came in, but seems like they used to be relatively easy to find. Maybe the price has gone up just for "Bronco" versions because of the popularity and pricing of the vehicles?
I don't know, but that still seems like an awful lot to gamble on an unknown and an out-of-state shipper.

Paul

Thank you paul for your help,i just saw it on facebook and was curious if it was a decent price but the guy sold it yesterday anyway and like you say with shipping and then with the reverse gear going out and who knows if the guy or the guy before him was lying,thanks for your help!

 

[rockinrich]

IF I decoded it right, B9 is 3.50 gears with the factory limited slip. Pretty common axle.
It won't be happy with 33" tires. Those are freeway gears for a Bronco.

that's what i planned on putting on was 33's because i have heard going any bigger you'd need to change your gears so you're saying i will need to change the gears to be able to run that size?

 

[DirtDonk]

Yes, and maybe.
Lots of people have run, and some are still running 33's and 3.50 gears. Been doing it since Broncos came out and 33's became popular.
Most are not impressed with the performance, but many are still accepting of what it is and drive it around daily like that. Partly so they don't have to pay the price of admission to a gear change operation.
Especially if they have to farm out the work to the pros!

Pretty much everyone though, even those that were fairly satisfied with the 3.50's, has the same thing to say about swapping to a lower gear... Usually something starting and/or ending in "WOW!" or words to that effect.;D

Paul

 

[DirtDonk]

And I'll say it again, that I bet my '68 would run just fine with 33's and 3.50's. And I'd love to try it someday to see if I'm right. But it's too expensive to experiment and takes too much time (because I work slow as molasses) as well.
But I've got a full-on Explorer motor with 4R70W auto transmission. So nothing like a stock Early Bronco engine and C4 combo.

As it sits now though, with just little 31's and 4.56 gears, all I can say about it would start and/or end with WOW!

Paul

 

[rockinrich]

And I'll say it again, that I bet my '68 would run just fine with 33's and 3.50's. And I'd love to try it someday to see if I'm right. But it's too expensive to experiment and takes too much time (because I work slow as molasses) as well.
But I've got a full-on Explorer motor with 4R70W auto transmission. So nothing like a stock Early Bronco engine and C4 combo.

As it sits now though, with just little 31's and 4.56 gears, all I can say about it would start and/or end with WOW!

Paul

lol,thanks paul,so i take it you'd go with 4.56 gears? lol,Now i get that those would be for the rear axle but what about the front axle when you're in 4 wheel drive would i need to change those out as well? Thank you sir!

 

[DirtDonk]

Yes, always!
The Ford rear end and Dana front ends (which are just repurposed rear ends by the way) don't always have a matched set, but the small differences are not a problem.
So you might have a 3.50 in one end and a 3.54 in the other, and that's just fine. But you can't even consider a 4.11 and a 3.50 because they are way too far off to be compatible.
At the best it would drive squirrelly in 4-wheel drive, at the worst it will brake something.

About the only time you do just a rear gear change is as a temporary test to make sure you like it before you spend the money on the front end. Lots of people have had to do it twice when they really did not like their choice of gears. It gets VERY expensive quickly, so doing just the rear on a Bronco is a good idea. Then when you know for a fact that you like it for your needs, then you do the front.

But no, in your case I would not go with 4.56's. I have an overdrive trans which lets me get away with it and still keep a friendly rpm on the highway. Even with the ridiculously low gearing for my tire size. About 29.5" in my case.
No, the 4.11 would probably be a better choice for 33" tires and a C4.
There is also a 4.30, but it depends on what you are going to do with the vehicle and how it's set up. More off-roading, the higher number is better. The more street, the more the lower numbers are better. But only up to a point...

If you have a carbureted engine that's old and tired with no mods, it likes the lower gearing (higher numbers) but if you've got a modern EFI setup with a good tune you can pull harder from a lower rpm and it runs well that way. Mine feels extremely strong, which is why I think it would tolerate the 3.50's. I know it would with the 31's, but I bet it would do just fine with the 33's as well.
Of course, it's kind of hard to tell for sure how much is engine torque and how much is gearing as it sits now. A 4.56 ratio is overkill-low especially for a street rig. It's definitely biased to off-roading and pulls so hard from a stand-still it feels unstoppable if you have traction.
Which is an issue on the street, as the tires break loose at the drop of a hat. Or the right pedal...

If you're going to spend 99% of the time on the street, plan to do some highway trips, and keep the C4, then going all the way to 4.56 would be somewhat overkill too.
If you intend to spend a lot of time off-roading and dune-jumping however, they might be just the ticket.

For comparison, a typical 33 inch flotation size tire (33x12.50-15 in other words) is likely about 31.5 to 32 inches overall height when mounted on the vehicle. Given that size here are the engine rpm ranges you would expect to see:
1. 3.50 @ 65mph = approx. 2500rpm
2. 4.11 @ 65mph = approx. 2900rpm
3. 4.56 @ 65mph = approx. 3300rpm

Number 1 is great on the highway, but would be sluggish off the line.
Number 3 is strong off the line, but revving too high on the highway.
Number 2 would be a good compromise.

When turning at those rpms on the highway, it sounds like your engine is screaming! Even at 3300 though, you're not hurting anything but fuel economy. However it sounds like it's close to redline according to most people who've driven their Broncos at higher speeds!
Even 2500 is a high rpm by today's standards, but common for an old truck. You have to keep a standard carbureted Bronco engine revved up to keep it feeling strong. And the 3-speeds of the C4 are always going to be a limiting factor. My trans with it's overdrive puts me at 2300-2400 rpm at the same speed, even with my smaller tires. Much more highway friendly, while still being super low for off-roading.
In the old days with my stock 3-speed manual and 32" rated tires, I spent a lot of time at 3,000 rpm and above when on the highway. Not a problem as long as you remembered your ear plugs and your gas cards!

Anyway, that's more info than you asked for, but it all plays in to your eventual decision on gearing. Normally I say change one thing at a time. Since we don't know how strong your engine pulls the best thing to do is keep the gearing as it is now, change the transmission and see how you like it.
But be ready to change the differential gearing if it's called for.

Paul

 

[Broncobowsher]

Paul's advise is solid. But I will add just a little. If you really are planning a NV3550 or other overdrive transmission that will play into the gearing as well. Paul's 4.56 with overdrive combo will net an effective ratio of about 3.23 which makes for a nice highway gear. But the actual 4.56 ratio is fun on the street and trail. (effective ratio is actual ratio x OD ratio)

I ran a 33" and 4.10 combo without overdrive for a few years. Was fun to drive. I could still run interstate speeds. These old school V8s are happy running that speed. The cooling fan just makes a lot of noise.
Later I went to the same overdrive that Paul is using and went to 4.88 gears. That was also a blast to drive, highway was better as the effective ratio was 3.42

 

[blubuckaroo]

This is where it's best to make a plan, for your build, and stick to it. Otherwise you can end up with an evolution of changes.
Back when I had a C4, I planned no bigger than 33" tires, because that's the limit for my 28 spline axles, and 2.5" lift.
The car was already poopy with 3.50 gears and 32" tires.
I knew that 4.11s would be fun, on the street, but a bit low for the highway.
I was considering something in between. There is gear options 3.70/3.73 or 3.89/3.92 for the Ford 9"/Dana 44.
If you plan to keep a three speed or C4, I would recommend either one of those combinations over a 4.11 gear set.

 

[rockinrich]

Paul,you never cease to amaze,you are a wealth of info and we are all very lucky to have you here,and thank you very much for the time you take to help everyone here,it's very much appreciated!Now as far as tranny's i'm not totally sure on going with auto that one deal got sold but right now i just have a 3 speed with about 88,000 original miles from what the older gentleman owner told me but it runs strong so could be true,anyways,is the original 3 speed just junk?I mean it is factory tranny,do people just want more out of a tranny,is that why they switch? Also if you were to replace it and mostly on road but want it capable off road would you go with an ax15 or nv3550?I heard jim at wild horses say on a video they are basically the same tranny,are there any differences? Thank you again for your help paul!!