No mechanic here, just a man with a truck.

I have a '78 F250 4WD, 351m. Since I bought it two years ago, I've been wanting to pull the C6 and put a ZF5 in it. Through various research I've discovered that the 351m calls for some custom machining to push the flywheel back into the tranny as far as it needs to go. (Knowledgeable corrections to this theory are welcome.)

Fast forward a bit: Two months ago I found a ZF5 S-42 complete with a married case. I was elated.

Now just this past weekend I inherited a '79 F350 DRW 2WD, 400. Is my suspicion correct that I'll be able to simply swap in the (newly rebuilt) 400, bolt up the ZF5 to it and scoot down the road with no custom work needed? (FWIW, I've already noticed that the input shaft on the old 4sp tranny is smaller dia. than the ZF's.)

Things just seem to be getting better all the time.

Thanks,
Jeff Bowman
Fairbanks, Alaska

 

Well this swap isn't just bolt in and go, unfortunately. For starters, you'll need to find a manual pedal assembly for your 78. The auto is different from the manual.

Next up, the ZF has a hydraulic clutch system and not a mechanical like these trucks had. That means there is a master and slave cylinder setup. The master cylinder goes on the firewall near the brake master cylinder, and has a pushrod that goes from the clutch pedal into it similar to how the brake pushrod works. Then a line runs down to the slave cylinder (internal for a small block trans, external for a big block trans).

The transmission crossmember will need to be modified/fabricated to accommodate the ZF. the older NP435 and T18 transmissions were shorter and smaller than the ZF transmission.

So it's not quite as simple as bolt in and go. If it was, more people would have done the swap.


-Jameson

 

the 400 isn't any different than the 351M, in that you should space the flywheel back 1/4" to 3/8", and at a minimum, space the pilot bearing out. What you are describing is exactly what I have done, and for me, everything that touches or is near the transmission had to be modified/fabricated. Im not quite ready to drive it yet, but am excited to cruise at 75+ mph!!

 

go to the 80 - 86 bullnose forum and look up gary lewis's thread dads zf swap. He seems to have the swap perfected

 

Hm... I was pretty sure it wasn't going to be a snap fit. Mostly what I was wondering about was the 400/ZF match. I was hoping it'd be better than the 351m, but I see by BigPerm's reply that it's the same situation. Phutz.



I may have that one solved; I may be able to use the setup from the '79. I'll look closer and see what I can find out.



I believe I'm going to be out of luck on that one. The owner of the auction yard where I got the tranny was careless, unfortunately. When he was swinging it around on a chain on his skid steer bucket, he dropped it in a pile of other trannies and broke off the top fork of the slave cylinder bracket.

Here, have a look:




I'm going to head back over there after the snow melts a month from now and see if I can find it. Then I'll have to find a decent aluminum welder who can tell me whether it can be fixed or not.

Since I'm considering a manual linkage, however, this may not be an issue at all. I may be able to just step around it. We'll see.



And that's another one. Grrr... he also broke off one of the little nubs that the frame mount bolts into. That one's going to be tougher, I think.

But wouldn't I just want to find a cross beam from a truck that shipped with the ZF from the factory? Seems like that'd do it.



Actually, all the other is peripheral (to me at least, at this point). The main thing is the 400/ZF matchup. And now that I've found out I'm in the same boat as with the 351m, well...

The fella who sold the ZF to the auction house still has the 460 that was in front of the tranny originally. He says he'll let it go cheap. I may just be better off to do that. But it's got original miles and the 400 is halfway through a rebuild. I like the idea of sticking a new motor in, since I'm going to all this trouble anyway.

Damn! Nothing's ever easy, is it?

Thanks,
Jeff Bowman
Fairbanks, Alaska

 

I might end up going back to get that 460. Might be I can do a little horse trading and get -it- rebuilt instead.



How'd you handle the starter?



That's exactly what I'm after--low RPMs on 4.10s at 75+

Thanks,
Jeff Bowman
Fairbanks, Alaska

 

That sounds like a good lead.

I believe I'll do just that.

Thanks,
Jeff Bowman
Fairbanks, Alaska

 

You'd need to check on frame widths. Also, the zf cross member bolts to both the bottom and top of the frame rail. You would need a way to drill holes to get bolts through the top.

 

Stock 79 cross member will work, just use the mount off the C6. Drill new holes in the cross member as the mount is further back on the ZF. If your C6 has the shorter transfercase adapter the ZF will be within a half inch in length. Notch ZF for NP205 shift rod, some have used manual clutch I think solidrunner did. I installed An 89 460/ZF in my 79 f150 4x4, dropprd right in with some L and L mounts and was only half an inch longer than the 351m/NP435 that it replaced. Got alot of help from this site just search around.

 

OK, sounds good.

Thanks,
Jeff Bowman
Fairbanks, Alaska

 

That's music to my ears :-)



I think that 460's going to be the way to go. I'd better go back and get it. I have neither the setup, expertise nor time to customize for the 351m/400. Of course, since my end goal is better mileage through lower RPMs, it may end up being a wash considering the 351m vs. the 460. Oh well...



Will do.


Thanks,
Jeff Bowman
Fairbanks, Alaska

 

FWIW, I went and bought a slave cylinder today and pressed it into the broken saddle. I wanted to see where the pressure points are.

With the flange around the cylinder that sits against the saddle's side, it doesn't seem like that fork's going to get a lot of stress. So if I can find it up there I may just be in luck. (I'm trying hard not to think about the broken cross member ear.)

I don't know much about aluminum welding, but I found some info at Lincoln's website. It seems I'm going to have to find out the alloy series for the ZF to even know whether it can be welded at all.

I imagine I ought to be able to find that data at the local dealer.

Thanks,
Jeff Bowman
Fairbanks, Alaska

 

You should be able to get the actual manufacturers name from your trans tag. Chase down your trans metallurgy through the manufacturer. They should be able to tell you exactly what kind of rod you need to weld that trans. I was thinking about the 400 zf combo myself until I found out it wasn't as straight forwards as I was told. I'm not in the position to afford a break down in that area. If it was a common swap that had a proven adapter kit, it may have been a different call as I like the light weight of the 400.

 

Nothing's ever perfect, is it? ;-)

I'll have a look at that tag.

Thanks,
Jeff Bowman
Fairbanks, Alaska

 

I busted out the threads around the transfer case shifter on the zf and had to get it welded. Took it to a Welder and he TIG'd it up for me. He said it was really nice aluminium to weld too. Cost me about $35.