Four Speed top loader in Bronco?

[Jr.mudflinger]

Could I replace my stock 3 on the tree that's hooked up to my stock 170 I6 with a Ford 4spd top loader from a 1966 Mustange coupe? Any imput?

Thanks
-Colton T.

 

[DirtDonk]

Should be almost a bolt-on proposition. Friend with a '69 is using one.
The 4speed might have a taller first gear, so that's not necessarily a good thing, but with the low-rpm powerband of the inline six, that might play into your needs if you don't off-road too much.
Better one-two shifts on the street usually, but not as good off-road.

Bell housing bolt pattern should be the same. Input should be the same. It's the output and the shifter that might have to be modified.
Not sure about the output and adapter to the t-case, but you'll need to swap to a 4-speed floor-shifter that you can get from Hurst or Duff. Duff's being the better choice.

Paul

 

[broncnaz]

X2 a toploader tranny has higher gearing and wouldnt be the best idea for a bronco especailly if you do any offroading.
Pretty much all ford tranny's from 65 up will bolt onto either 6cyl or V8 bellhousings. input shaft is the same but to convert to a toploader you need a output shaft and have the stock V8 intermediate housing machined for a larger bearing. I've yet to hear of anyone using a 6cyl housing as it 3in shorter than the V8 housing and none makes a output shaft for it.
If you do this swap I would be interested in the mustang tail housing and output shaft. or at least the tailhousing. Might even be up for some kind of trade as I have a toploader setup for a V8 bronco sitting in my shed.

 

[Jebus]

The six cylinder 3 spd box itself is a differen't length than the V8 box, it is approximately 1 inch shorter.

 

[Broncobowsher]

The six cylinder 3 spd box itself is a differen't length than the V8 box, it is approximately 1 inch shorter.

But that isn't the issue.

The output shaft and adaptor length are different. All the conversion pieces out there are for a V8. So you will be looking at doing a V8 length transmission in all likelyhood. That pushes the transfer case back about 3". This is how it is done when swapping a NP435 into an I6 powered Bronco.

I don't know if the toploader output shaft can be shortened 3" to use the I6 tailhousing. It might, but I am doubtful until I see one. As far as I know it would be a first, and that is not that common with a Bronco.

 

[Explorer]

I do know of one. "Broncitis" over on fordsix.com is running one behind a turbo charged 200ci I6. He is from Raton, New Mexico. Talked to him when I started my 66 build, but I have long forgotten the specifics of doing it.

 

[Jebus]

But that isn't the issue.

The output shaft and adaptor length are different. All the conversion pieces out there are for a V8. So you will be looking at doing a V8 length transmission in all likelyhood. That pushes the transfer case back about 3". This is how it is done when swapping a NP435 into an I6 powered Bronco.

I don't know if the toploader output shaft can be shortened 3" to use the I6 tailhousing. It might, but I am doubtful until I see one. As far as I know it would be a first, and that is not that common with a Bronco.

I know that is not an issue, was just sayin, and the output shaft is. It is better to go with the V8 parts for a TL four spd conversion. This keeps your crossmember closer to the same location. The transfer case does not change location, just the tailshaft housing is different. I just changed my six cyl setup to the V8 3 spd parts, to install a 3.8 SC engine. It's in place and the crossmember and transfer case is in the exact same location.
The best bet for a TL 4 spd conversion is Toms. Then you bolt up to V8 3spd housing. Kinda spendy, but you will have fewer headaches if you do.

...JJG

 

[broncnaz]

But it is a issue when your keeping the straight 6 cyl motor as you will have to move the crossmember close to 4in using the V8 adapter. In your case when swapping a V6 then yes the V8 adapter is needed because the V6 doesnt clear the firewall like the straight 6.

 

[Jebus]

Ahh, understood. Would using the V8 short trans tailshaft and a shortened spud shaft work for this?

 

[broncnaz]

It will work for your 3.8 swap just fine but for the straight 6 he would have to move the crossmember. as the tranny probably wouldnt reach the engine if you try to keep the corssmember in the stock location.. Shouldnt need to shorten the spud shaft. its been awhile I cant even remember how long the inner splines are but I would want as much spline contact as possible.

 

[Jebus]

It will work for your 3.8 swap just fine but for the straight 6 he would have to move the crossmember. as the tranny probably wouldnt reach the engine if you try to keep the corssmember in the stock location.. Shouldnt need to shorten the spud shaft. its been awhile I cant even remember how long the inner splines are but I would want as much spline contact as possible.

I did not say to use the tailshaft housing from the V8, that would be even longer, just the TL car 4spd 4x aftermarket output shaft. The inline six cylinder engine package is longer than the V8 package. Thats why the six cylinder tail housing is shorter.
The TL car 4spd is 1 inch longer than the six cylinder bronco 3spd box, minus the tail housing. How would that make the package too short, if keeping the inline six cylinder?
Slipping the TL car 4spd box in place of the 6cyl bronco TL 3spd, keeping the six cyl tail housing makes this package 1 inch or so longer. The only issue I see is the rev shift rail (doesn't it stick out into the tail housing when engaged?) and connecting the output shaft to the spud shaft. Look at the pic I posted. Not trying to argue, we may be sayin the same thing.

You are correct on my V6. It is in just fine using the V8 trans package. I started with an inline six cylinder.

 

[Boss351]

I have a shortened toploader output not pretty but works great forsale if your interested call Rob 508 962 0972

 

[broncnaz]

Right but the issue is no one makes a 6cyl lenght output shaft for the 4sp. thats the whole hangup on the swap if they made the output shaft then using the 6cyl housing would work. There was someone saying that the later 4sp OD trannys out of 4wd trucks have a bigger output shaft that could be resplined and shortened to work but I dont believe this swap has been finished yet. so the jury is still out on that. not to mention that theres a little more involved than just resplining a shaft as they should be rehardened so the splines hold up. the 1in differance in transmission lenght between 3and 4 sps s usually not a issue as the crossmember mounts are slotted worst case you may need longer slots.
Overall the 4sp toploader is not the best swap for either a V8 and especailly not a 6 cyl. the first gearing is worse than a stock v8 3sp and way worse than the 6cyl 3sp. any offroading at all and you really wont care for it. Thats why went to a NP435.

 

[Ranchtruck]

If you go with a mid-late seventies toploader with overdrive, you get lower 1st and overdrive. That's a better swap than putting in a normal toploader that has the same overall gear range as the 3 speed, just more shifts.

Here's how to ID one:
http://www.davidkeetoploaders.com/imposters.htm

People run them behind 460's, so I don't think the strength was reduced any when they swapped 3rd for an overdrive.

Overdrive lets you run lower gears in the differential without overrevving on the highway. Lower gears in the diff makes up for the lack of a granny first gear.

 

[Explorer]

Ranchtruck: His stock little 170 just isn't going to be able to use the overdrive.

 

[broncnaz]

X2 thats one of the issues with trying to use a OD toploader behind a 6cyl. While I dont doubt people use the toploader OD behind 460's a 460 has lots of lowend torque and will push just about any vehicle happily along in OD. but its by no means a performance tranny wouldnt want one behind a well built 460. Also have to consider that few people want to swap transmissions and axle gearing especailly in a 6cyl. Dont even know if you can get low enough gearing to make it feasible especailly if you run larger than stock tires.

 

[Jebus]

Could I replace my stock 3 on the tree that's hooked up to my stock 170 I6 with a Ford 4spd top loader from a 1966 Mustange coupe? Any imput?

Thanks
-Colton T.

LOL, and he asked for any input...
In short, yes you can...

 

[Explorer]

With my own engine, 4:11 gears and 30" tires, I could handle a wide ratio 4 speed toploader. The .81 overdrive would be entirely useless till faster than 80mph. Engine was designed for the torque curve and peaks at 2850rpm. 65mph in overdrive would put me 550 rpm below my peak torque. But there is a big diff between a stock 170 and my built 200.

 

[Ranchtruck]

Ranchtruck: His stock little 170 just isn't going to be able to use the overdrive.

Explain to me how it's going to use a 2.78 first in a toploader better than the stock 3 speed 3.41 first? Stock 3spd with 4.11's gives a 14:1 first reduction. Toploader gives a 11.4 first reduction, which you need a torquey engine to be able to pull off without smoking the clutch all the time.

The point of an OD is not faster highway speeds. It's being able to run really low gears in the axles without loosing highway speed.

So he could run 5.38/5.43's with the OD, which would work out to a 17.85 first gear reduction, and in OD be the equivalent of having 4.39's with the stock top gear. That's a decent improvement without loosing highway speed.

Now run the 2.5:1 low range into that, and you have a 44.6:1 crawl instead of the stock 35:1 crawl.

 

[broncnaz]

There's a whole lot more to OD than lowering engine RPM's and it does have to do with going faster. It s not like OD is used for going 10 mph. the problem is the engine(170ci) itself it has to run in the higher RPM ranges to push the bronco. That 170 just doesnt have the omf to do it and it take more torque to run in OD than it does in 1-1. yes lower axle gearing is required in most cases but on that note why would you spend the money to swap a tranny in swap gearing in when the outcome is virtually the same as staying stock your only getting one more gear to shift into and a slightly better gear reduction on the lowend. really the only thing lower axle gearing would let you do is run bigger tires and possibly still be able to use the OD function. You could just stay stock and go with bigger tires and get a free OD. Then if you find its not working out then axle gearing and tranny swap may be in order, but engine torque output has a lot to do with it. if it didnt we'd all be running 4cyl engines with OD tranny's