Power Limitations of RAT/RAN Transmission

[R-Banger]

Hello everyone,

Tried searching but couldn't find anything on the forum regarding this. My 289 is getting pretty tired and on it's last leg so I am planning on doing a 1" body lift and squeezing in a 408 stroker. My brother in law needs a new engine for his 65 mustang so we are going to yank and rebuild that for him while I build my stroker. My question is how do the RAT/RAN transmissions hold up behind a 500hp/tq engine? Do they have clutches that can hold for this kind of power for these transmissions? It's not getting drag raced or anything, just making it more fun. 90% street driven and may take it on some trails here and there. I am very attached to my column shift so would really like to not get rid of that if at all possible. Anyway, thank you in advance for the help.

 

[1969]

Can’t answer to the strength of them but would suggest going to an AX15 or similar transmission to improve the drivability of your Bronco.

 

[Broncobowsher]

The 3-speed is pretty much a top loader 4-speed but with less gears in it. Really strong. The big block toploaders had a larger input shaft. But the 3-speed uses the same size input shaft as a small block top loader. There isn't an exact value they are rated at, but there really isn't anything bad in them. Ford offered the 3-speed factory behind the 390. Now the transfer case output shaft, that will fail first.

There are clutches out there that can take the power and send it through the 3-speed. I'm not up to date on the latest offerings. But they do exist. There is stuff that will take over 1,000 ft-lb. I doubt you are anywhere near that.

Just because you can do it, should you do it? Have you ever driven the stock 3-speed?

 

[R-Banger]

Appreciate the feedback! Looks like 500/500 shouldn't be an issue for the transmission. Honestly I have fun fast floor shifts when I want to drive hard. I use this car to go to the beach and the office daily. It really is just my surf wagon, not looking to slam gears and haul ass in it on the freeway. However, would love it to really have some pep in its step when I drive it and want to pass etc. Figure if I am going to spend the money on getting a 351 might as well through some more cubes while I am in there. With the weight of the truck feel like 500hp would make it fun and be able to at least keep pace with modern cars these days.

 

[Apogee]

Regardless of how much power the engine makes, how much traction do you have? At the end of the day, the transmission is only going to see the amount of power you can put to the ground, and the RAT/RAN transmissions are not exactly expensive or hard to find if you ever blow one up and need a spare or two or three.

 

[R-Banger]

That was exactly my thoughts. It's not going to be hooking hard or launching. Suspension is upgraded so hopefully won't wheel hop horrible if I punch it, but definitely not going to be hooking up hard. Also a good point I didn't think about, if they are cheap and easy to get I don't mind the risk of it blowing up. Now just need to find a clutch that won't slip at least. I don't want to deal with burning up clutches super prematurely.

 

[DirtDonk]

Replaced my original clutch with one from McLeod and loved it.
Heavier pedal, but I was younger so that didn’t cause me any trouble. And I’d already upgraded the pedal rod because the original had failed with the stock clutch not long before.
These days I’d probably just use a Centerforce II or III for the lighter pedal pressure.

 

[DirtDonk]

But back to the torque rating/capability of the three speed, what differential gear ratios and tire size are you running?
This has a big impact on how much of that pressure from the engine the transmission actually feels.

 

[R-Banger]

I am running 31X10 inch tires nothing crazy. Don't know the gear ratio. Will have to get it up on the stand and spin. Most likely whatever it came with from the factory as the previous owner didn't upgrade anything on it other than put discs up front. Will probably upgrade to 33s at some point but that'd be the largest I'd go.

 

[DirtDonk]

Probably 3.50 or 4.11 then.

 

[R-Banger]

Gotcha. Appreciate all the help with this! Will start putting together the parts list....

 

[roundhouse]

I ran a stock 351w and the stock 3 speed for years .

Had the shifter on the column for a couple of years then got the James Duff floor shifter

Adding power steering and the floor shifter made it feel like a sports car