I've recently completed a swap from a C6 to a ZF5 out of an 88 F250 in my 79 F250 4x4. I'll post a few thoughts in hopes that they'll help the next guy. First, many thanks to FTE posters SolidRunner, 77f150got_sand, and kenmt. Without the pictures and information posted by these guys, I doubt I'd have even tried the project.

First of all, when converting from auto to manual, you will need to have driveline work done. I read in the previously mentioned folks threads that they didn't, but I think they were all going from manual 4 to manual 5spd. The ZF assembly is about 2.5" shorter overall than the C6 assembly.

Crossmember- Its been mentioned by the posters listed above that you do need to modify your crossmember attachment. My approach to this was to attach the crossmember attachment components from the C6 to the bottom of the ZF and then bring the crossmember up underneath them. Then I just welded the two pieces together. This isn't the most elegant solution, but it does work. Also, this connection is a bit redundant in a previously automatic truck as there is a transfercase "strut" that ties the transfer case to the frame and provides much of the support between the rear of the drivetrain and the frame. Also, I've checked, and my welded solution is removable for tranny service, etc.

Clutch and Flywheel- As has been noted many times, the 460 switched from an internal to external balance configuration around 1979. My engine is the older internal balance. My first approach was to take a late model 460 flywheel and machine off the balancing steel, but what I didn't realize is that the bolt pattern on an externally balanced flywheel is not the same as the internally balanced crankshaft I have (which makes sense, as you need to get the external balanced flywheel indexed properly to maintain engine balance) My next approach was to buy an internally balanced 460 flywheel from Jeff's Bronco Graveyard. (turns out this is made by L&L) This arrived and didn't have the 8 hole clutch bolt pattern of the factory late model clutch, so I was foiled again. I ended up contacting L&L products directly and purchasing a custom clutch to fit their flywheel. All of this ended up being quite expensive, so I'd advise trying to make something else work. Possibilities include starting with an externally balanced motor and using entirely factory clutch and flywheel components, or trying a 390 flywheel and having a custom clutch made locally. Moral of this story is that factory ford clutch for 5spd equipped trucks will NOT fit the 460 internally balanced flywheel that JBG sells.

Pilot and throwout bearings- Stock 1988 components work fine

Clutch Fork and Linkage- Due to an intense dislike for Ford's hydraulic clutch setup, I went with a manual clutch linkage for this project. I sourced a pedalbox, clutch pedal, and complete linkage off of ebay (junkyard would also work) Changing the pedal box from auto to manual proved to be an absolute nightmare, so in hindsight, I might have tried the hydraulic clutch. In the end, what I have works. I made my clutch fork similarly to SolidRunner and got_sand, but I didn't have a 4spd fork to start with, so I sectioned the ZF fork and added exactly 3 inches to it using some channel steel. One note about this: I didn't want my clutch fork to ever break, so I used a LOT of steel to section it. Problem is, its now quite heavy, which makes it hang down out of the bell housing. So far, with all the linkage buttoned up, this hasn't proven to be a problem. For a clutch rod, I used a heim joint to connect the equalizer bar to the clutch rod to prevent binding, then I built a sleeve to connect the heim to the threaded rod. At the fork end, I took a 3/8" bolt and ground the head into a mushroom shape similar to the plunger on the hydraulic slave cylinder. I recommend if using manual linkage that you replace all of the bushings in your linkage. I got all mine from LMC (yeah, I know they're a dirty word around here) for about $10.00. So far, everything works, so I must have gotten something right. Additional note: I did have to cut off one of the slave cylinder mounting ears in order to mount the linkage to the ZF, but once that was done, everything lined up perfectly.

Driveshafts- As mentioned above, the ZF is about 2.5" shorter than the C6 so I had to have my driveshafts modified.

Transfer Case Mounting- This has been largely covered by the previously mentioned posters, but I'll touch on a small change I had to make. The transfer case shift lever does mount on the ZF case just fine, but the linkage connecting the shift lever to the t-case was about 3 inches too long, so I had to shorten. I cut 3 inches out, butt welded the remaining pieces, and welded a sleeve over them for strength. Be careful to maintain proper rotation of the rod ends as they don't point the same direction.

Wiring- Backup light plug socket for the ZF is available from LMC.

Fitment/Finishing- As mentioned by others is the the cab "flange" needs to be cut and bent out of the way to allow the tranny to fit. My addition to this is to do this before you mount the flywheel, so you can be a bit more effective with the hammer. My truck had a tunnel cover for an auto, so all I had to do was locate and cut the hole for the tranny shifter. I also had to enlarge the transfer case shifter hole toward the drivers side because the shifter sits farther over on the zf than it did on the C6. My original plan was to mount a late 70's shifter to the tranny for "period correctness" and use a 70's shift boot and trim ring. The problem is the shift tower on the zf is too tall for this to work. So since my zf boot was torn beyond recognition, for now, I only have the inner boot on the shifter. I'm looking for some sort of universal boot that is round, so I can use the stock trim ring. Much easier said than done.

That's all I can remember for now, but if you have any questions, please ask. Unfortunately, my wife had my camera during this process, so I have no pictures, but I can probably take some after the fact if specifics are requested.

Again, many thanks to those who've gone before me.

 

Thank you for the write up. I would have been in the same position as you with my 73 460 and the flywheel problems. As far as your shifter boot goes. Down at our local parts store (NAPA) the sell " Universal Shift Boot " Its about 14.99. I hope everything stays in good shape for ya and have fun!

 

Transmission finally in place
Zf5 notched for shift rail
Pilot bearing and my nick in the 1991 flywheel bolted up to my 70s crank.
My shortened rod between transfer case a shifter
First off I'm glad there is this forum! I can't say enough about the valuable information I learned about projects that others have done so that I could copy their recipe. I have a 1978 f250 4x4 460 / c6 combo that I swapped in a zf5. My zf5 came from a 1991 f250 4x4. I harvested the transmission, flywheel, shifter, and hydraulic clutch system. I did a write up on how I tackled the hydraulic system to make the zf5 work. I have a family member that has a hoist and I feel without access to this there would be no way that I could lay under my truck to get this project accomplished. I would also like to say that I am not an accomplished mechanic, but thankfully my uncle is.

460 - not real clear on the history of my block and crank, I believe it to be a 70's. I took my 1991 flywheel and had the balance weights taken off and rebalanced. It bolted right up to my crank with no issues. The 1991 pilot bearing was a pain to get in. I accidentally hit my flywheel with a hammer when I set the bearing. You can see a small nick in the flywheel in my picture. The slight nick in the flywheel thankfully has not affected it's balance.

Clutch - brand new 1991 f250 sach replacement

zf5 - I cut off the firewall pinch weld with my cut off wheel. Getting this tranny in this spot is a pain. I loosened the motor mounts, dropped the exhaust, and than but a jack on the front of the motor so as to tilt the motor down to help line up my tranny. I was scarred it wasn't going to fit.

driveline- front one needed about an inch cut off and the rear needed 3 or so inches more.

transmission crossmember - if I had better fab skills I might have built my own. I slid the crossmember back a couple inches a redrilled my holes. Not too bad. Had to take out the frontbody mounts and pry between the body and frame to get the crossmember top bolts in. Be careful I squashed my finger pretty good.

Transmission tunnel. Cut a hole for the shifter. The 1991 gear shift looks like it is suppose to be there. No problems with banging into the dash or anything else. I did have to modify the transfer case shifter. i had to englarge the hole towards the seat because the transfer case now sits back a a little further. I'm in the process of rewelding some sheet metal back in on the front side near the gear shifter to make it a little cleaner. I will include a picture of this when I'm done. I'm not a welder either! I thought this might be nice for people to see.

If anyone wants a specific picture of what I have done let me know soon, cause it is coming of the lift hopefully tomorrow.

 

well I got my project all button up. My transfer case shifter got moved down because the zf5 is slightly shorter so added a patch panel to the front of that hole. I now have driven it and apparently everything works great. Now looking forward to my 4bt motor swap!

 

I used the 1991 f250 shift boot that I harvested from the truck I got the zf5. I had to build a 2" box to set the boot on for it to work with tranny cover. Unfortunately when I originally put my vinyl floor down I had cut the hole for the c6 / np205. Now with the zf5 /np 205 it changed the location slightly. I have the bigger hole covered with carpet for now and will possibly replace the vinyl when I have more $.

 

I hate to tell you this now........If you do end up going to a 4BT......You could have left the shifter holes and fore/aft mounting of the trans in the stock location....The only thing I had to do on mine was re drill the 3 holes where the transfer case mount on the drivers side attaches to the frame........they had to be moved back about an inch.....Then I had to trim a piece off of the drivers side hole in the floorboard that is covered by the trans tunnel.......this piece I trimmed was about 1/2" wide by about 8" long.....Of course I had both the 4BT and the ZF5 to install at the same time.....so I spent a lot of time juggling them around to find the "sweet spot" that required the least amount of modification......I'm currently working on mating my old 4 speed stick to the ZF5 shift stub.....I'm wanting to keep it looking original too......we shall see how my boot situation turns out.....I DID NOT want to butcher up my truck to do the swap......I'm sure the ZF5 is the best mod you have done to your truck!!!! And BTW....nice job!!!

 

I want to 5 speed my crewcab

 

I would think the process would be the same for your truck as mine. I built my set up in stages. I first found a 70's clutch assembly and built the hydraulic set up that I needed for the zf5. I did as much as I could before I crippled my truck. I than found my 1991 f250 donor truck parts and had them rebuilt or revamped for my purpose. I am no mechanic and without a lift I'm not sure I could have accomplished this build.

 

What transfer case did u use

 

I used the stock married np205

 

Did you notch the case. ?

How close are you to north Texas ?

Would love to see eyes on !

 

Yes I notched the case so the 4x4 shift rail would clear the zf5 transmission. I unfortunately live in Vancouver, WA very far away from Texas. I do enjoy working on others trucks to help with my own learning process.

 

Just got an 85 F-250 this afternoon. Price was right so didn't mind the C6 that it has. Had a 300-6 in highschool so this brings back memories.

Love the swap! Glad there is a more HD 5psd than the Mazda tranny. Might do this next summer will definitely hit you up!

 

Great work .. do you have any images of the clutch linkage you used and what side you fitted it on ? Thank you very much