Greetings fellow Mustang Fans. First time posting here, looking to pick your brains on a topic.

I am interested in making the 4th gear in my 4 speed Toploader into an "overdrive" gear. I have read on the net that one can take certain gears from a later model 4 speed toploader and install them into a conventional toploader, resulting in a 1 to 1 3d gear ratio and a .82 to 1 fourth gear ratio.

Has anyone out there tried this? Does it work? Or will the power of a 428 CJ motor snap the gears like twigs?

Any information or other ideas would be greatly appreciated.

Thanks

 

The overdrive toploader from the late-70's used a thin overdrive gear where 3rd normally was - activated by reversing the 3/4 shift fork. By all accounts, it's extremely weak. Not good for performance use at all. Some info here.

If you're dead-set on a toploader, I'd recommend dropping an email or phone call to Mark at Toploader Heaven - good guy. If anyone knows how to do this, it'd be him.

Why not just use a TKO-500/600? Met a guy last year with one in his GT500 - worked out pretty slick...

 

TKO can handle it no problem and it's got 5 GEARS!

 

Weak gears, that's what I thought when I heard the gears had to come from a 70's vintage transmission. You confirmed my suspicions.

My delimma is this....I have a 1970 SCJ Mustang. A rare car no doubt (1 of 857). The car has 3:91 gears and I hit 4500 rpm at about 65 MPH. That means you are getting passed by VW's here in Southern California.

I don't want to do anything to the car that would require cutting up the floor pans. I was hoping that I could just switch gears but I also figured that if it was possible, someone would have thought of it already.

So I guess I will continue to research this project. And I thank you all for taking the time to give me your input. Every suggestion and opinion is appreciated.

Doug

 

you shouldn't have to cut anything to fit the TKO in a 70. it was only the 65-66 cars that had the big problems.

 

The 5-speed's should work w/out a prob., but if you are dead-set on a top-loader, you should look into a Jerico. The NASCAR boys use'em all the time w/ od. on the Superspeedways!! Sorry, no link but I'm sure you can find out something, just Google it. John

 

A Jerico. *blink*
________
Live sex

 

How are you intending to use the car? While I agree a TKO 5spd is probably your best bet to solve everything and would be unoticable with a stock shift ****, your 3:91 gears are really designed for 1/4 mile driving. While a 428 is never going to be a practical cruiser no matter what, just swapping to a more conventional 3:50 gear set may at least get you another 10 to 15 more MPH at the same RPM's you are in now.

 

Yea, I know, Jerico=$$$, but the guy said he was looking for ideas. Its a custom tranny based off the top-loader. Just putting my 2 cents in, I've heard of guys driving them on the street, just not often. And I agree, put some higher gears in it, 3.50's or even 3.27's should help a lot, especially w/ that stump puller of a motor.

 

I plan on just driving this car around town, but an occasional road trip is also planned. I'd love to be able to drive the car on the freeway, but I am torn between keepiong the car looking original, and modifying the car so I can enjoy it.

I am not opposed to bolting on stuff that can easily be changed back to stock, but I will not start cutting and chopping on the sheet metal. The car is just too valuable for that.

I guess I have a problem that most classic car owners have, Keep it stock i.e. gas guzzling quarter mile bruiser, or upgrade to a more modern and more driveable car.

I'm not complaining either way, just looking at my options and all of your input is appreciated.

 

With today's technology, putting a modern 5-speed in is not that bad, and can be returned to original also. Swapping rear gears is even easier, and has been done for years. With a 9-inch, you could just buy a complete center section(also called pumpkin, third member,etc.), pull the axles and just unbolt the driveshaft and center section, then install the new one. No cutting or messing up your classic!!

 

If your looking at doing a 4 to 5 speed conversion check out Modern Driveline. Modern Driveline

They have all the parts you need to do the conversion. I would go with a G-Force T-5 if I were going to do the conversion. THe G-Force T-5 is good for 600ft/lbs of torque and it's lighter than a Tremec.

G-Force Transmissions

 

If you want to do an easy bolt-on and keep it stock - go to 3.0 or 3.25 gears. Easy swap, no cutting, save the originals in a box, and that 428 will make burnouts no problem.