??'s about Car style Toploader 4 speed into 72 Long Bed

[frankentrucks]

Hello,

New to the site, but not to 60's-70's Ford cars and trucks. I recently picked up a 72 F100 long bed with a small block and a 3 on the tree. I have a cherry RUG toploader 4 speed out of a 72 Mustang that I am planning to swap in. I know this will require cutting a hole in the floor, and I'm cool with that. I also know that I'll have to fabricate a shifter mount and linkages to put the shifter where it needs to be, ahead of the seat.

My question is regarding the drive shaft. Being a long bed, this truck currently has a 2-piece driveshaft with a short tailhousing transmission with a fixed output yoke. The new Mustang toploader has a long tailhousing and takes a sliding output yoke. Drievshaft mods will be necessary.

My questions are:

1) Should I replace the 2-piece driveshaft with a really long 1-piece shaft? I am worried about harmonics with doing doing so.

2) If I decide to keep the 2-piece shaft, are there any issues with shortening the front piece of the shaft and converting for compatibility with the slip yoke? Will this potentially cause pre-mature failure of the carrier bearing between the two shafts, as there will be a potentail for motion for and aft, as each half of the driveshaft will allow movement?

Has anyone here had any real world experience with a similiar swap in their trucks?

Thanks in advance, Brett

[67mann]

Kinda curious what people got to say about this,because I put RUGM3 behind a 390 in my project truck and plan on just shortening the front shaft. There is a difference between truck and car bellhouses that could cause a problem with your input shaft length...at least as far as FE'a are concerned..not sure about smallblocks. A smallblock toploader will work with a bigblock and it's bellhousing,but a bigblock toploader will not without changing the input shaft or bellhousing

[frankentrucks]

Yeah, I'm aware of the input shaft length concerns as well. Like you said, the big block toploaders had a shorter input shaft, and corresponding shallower bellhousing, than small block toploaders. The small block toploaders and truck transmissions all had the same input shaft length, and in fact many small block equipped cars used bellhousings with truck part numbers. Only reason I can figure for Ford to do this would be either to avoid potential assembly line mix ups with the sturdier and more expensive transmissions in the lower powered cars, or because of firewall issues in the cars that required a shorter bell. Who knows? The trans I have came out of a 351C car that should have used a D1TA bellhousing, so I should be good there...

Thanks for the input.

[frankentrucks]

67mann and I can't be the only people to ever attempt this...

[67fordkc]

I have a small block toploader RUG E3 behind my 390 and have the two piece drive shaft. I had it shortened and have had no issues with driveability. It runs up to 90 mph very fast and smooth.

[Nitekruizer]

I have a small block toploader RUG E3 behind my 390 and have the two piece drive shaft. I had it shortened and have had no issues with driveability. It runs up to 90 mph very fast and smooth.

• So you're using a slip yoke at the transmission?

[67fordkc]

I have a small block toploader RUG E3 behind my 390 and have the two piece drive shaft. I had it shortened and have had no issues with driveability. It runs up to 90 mph very fast and smooth.

• So you're using a slip yoke at the transmission?

I am using the original setup for the long bed to include the short drive shart, carrier bearing and the long drive shaft. I had the short drive shaft shortened that goes from the transmission to the carrier bearing. I purchased a slip yoke from David Kee Top loader website to connect the short drive shaft to the transmission. Does that give the info you were needing?

[frankentrucks]

Thanks for the info on your personal experience, 67fordkc. I was leaning toward doing the exact same thing. Glad to know it works!

[67mann]

Thanks for the info on your personal experience, 67fordkc. I was leaning toward doing the exact same thing. Glad to know it works!

X2

[67fordkc]

No problem guys, glad to help. Let me know if you have any other questions and I will do my best to help. If you need photos of the install let me know and I will take some. Have a great Memorial weekend!!!

[frankentrucks]

Yeah, if it's not too much trouble, pics would be awesome! Especially of the shifter brackets and mounting location. I plan on keeping the bench seat in mine, was figuring that I'd make a bracket to put the shifter as far forward on the tailshaft housing as possible, in a similiar location to where the early Falcon/Comets placed them.

Thanks again, Happy Memorial Day to you too! And to all of our service men for that matter...

[frankentrucks]

Finally got around to completing the swap this weekend. Like what was said above, I merely shortened the front section of the driveshaft and installed a slip yoke to mate to the transmission. For the shifter, I used the mounting bracket from a late 70's 3+1 overdrive toploader (originally installed in vans and trucks, moves the shifter far enough forward to clear the bench seat) that I modified for use with a Hurst shifter. Shifter pops up far enough away from the seat to allow adjustment, but isn't buried under the dash either. An early (64-65) Falcon/Comet tailshaft housing and shifter would probably work too, but those are rare and expensive. I was able to use the stock crossmember, just drilled 2 holes to work with the Mustang rubber isolator (the tailshaft housing on my 72 Mustang trans wouldn't take the stock truck mount, some earlier ones will). Everything works great, so far. I overlooked needing to swap to a left hand rotation speedometer driven gear, and haven't wired in the backup lights yet, but other than that I'm pretty stoked. HUGE improvement in driveablity with the tighter gear spreads and syncronized first gear. First gear isn't quite as low (2.78 vs. 2.99), but I have a 3.50 rear gear, so it's not really an issue.

[gregamorton]

I just got mine done last week. I put a rug 3 speed od behind a 300 and put it in my crewcab. My truck was a 390 4 speed np435 with a 2 piece drive shaft. I bought a new slip yoke and had the front short piece shortened and balanced with all new u joints. I have not cranked the 300 yet but I hope there is no driveability issues. I think the front shaft was around 20.5" center to center on joints.

[Freightrain]

I put 4 spds in a couple long bed trucks. Yup, got me another front shaft, had it shortened and fitted with slip yoke on the front. Bolted in, worked perfect for years.