87 F-350 C6 to ZF-5 Conversion + GV Overdrive Build Thread

[bookite03]

So here goes...been wanting to do a ZF 5-Speed swap on my 1987 F-350 CrewCab 4x4 since I bought it. Currently I have the original 6.9 with a strong C6 and a Gear Vendors OD behind it....but slush boxes aren't really my thing. I've been averaging 14ish mpg mixed driving, I'd like to see if I can improve that with some good shifting technique and running my current GV Overdrive behind it. Essentially having a double-overdrive of sorts.
Browsing Craigslist I came across a donor 88' F-250 Reg. Cab 4x4 with a newer ZF and transfer-case behind a N/A 7.3...axles/suspension/tires had been robbed by the previous owner, but that's not what I'm after. So we agreed on a price and the truck was delivered on Saturday.

Got it up on some stands and started the dis-assembly with Leeland another member on here, the sheet metal is surprisingly straight with no rust....it's too bad I can't use it. Hopefully I'll be able to sell some parts and get my money back on this project. Currently plans are to tear down the donor truck, pull the transmission/t-case and all parts necessary for the swap. Going to toss in a new clutch, hoping the flywheel is good to go... we will see when I get there. Anyways, here's a couple progress picks. Any tips along the way are always appreciated.

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[towcat]

you got all the parts there for a drop-in install. don't forget to surgical out the wiring harness off the trans. it's a plug-n-play unplugging the C6 stuff and plugging in the ZF goodies.
now you're going to hear the east coast guys howl about a reg cab truck getting killed for parts.

 

[bookite03]

Those east coast guys can always pay for shipping

 

[towcat]

Those east coast guys can always pay for shipping

only when hell freezes over.
i've been listening to them for years here.

 

[laserjock]

As predicted...



Got any use for the cruise control parts.....

 

[franklin2]

I hope you have a strong engine. My truck has a zf with 4.10's and 35 inch tires, and it barely turns over at speed. I don't know how hilly it is in Oregon, but here I barely make it up and down the hills around here empty in overdrive. I guess it would be ok if you never used the overdrive in 5th gear.

I think I would swap the zf in first by itself and try it out. And then add the other overdrive later if you though you needed it. My truck originally had the c6, and I was getting 12mpg. I swapped the zf in place, and with no other mods, I am now getting 15 mpg. So your torque convertor slip you have now might be that 1 mpg difference.

 

[bookite03]

As predicted...



Got any use for the cruise control parts.....

Nope cruise on my crew already works well...pm me if you're interested.

Franklin - my truck already has no problem turning over the 33's on it now...a friend has a ZF and his rpm's are similar to mine with the C6 and GV. I'm mainly planning on using the 2nd overdrive on long flat stretches and a 4th or 3rd over depending where the speed and rpm but me and if its within the operational range of the unit. Going to be a lot of trial/testing.

 

[Dieselcrawler]

my NA motored 86 when it was street legal had NO issues with 40's and 3.55 gears... you got something up with yours franklin

 

[smokin150]

Is the engine still good? I might be interested if it ain't *****'d and your not going to use it...

 

[stuborn nut]

That's the same thing i was up to this weekend 86 c6 to a zf5 all went great until I got to the down pipe and floor pan. Older pan hits top of the tranny newer one doesn't fit the carpet.I wish I would have worked over the firewall a little before I put the tranny in. Never thought about the bellhousings being a little differnt shape. I used the 208 t-case that was in the pickup already driveshafts and everything fit nice. I gave up midday monday. The kids and wife will be away next weekend should be able to finish then. I hope.

 

[Dieselcrawler]

yep, the removable plates are different on the floor.

 

[Leeland]

Has any one tried soaking it and hitting it with a heat gun to reform it?

 

[towcat]

Has any one tried soaking it and hitting it with a heat gun to reform it?

not so easy.

 

[Leeland]

Figured I'd ask if it's been done.

 

[bookite03]

Once I get the transmission and necessary parts pulled I'll start doing inventory and make a thread over in the marketplace for what I have left....

The carpet fitment crossed my mind, the new tunnel cover is definitely taller. I was hoping a few creative cuts here and there would get the job done.

Another thought through the process, am I going to run into any issues running the 7.3 flywheel on my 6.9? I know this subject has been beaten to death in multiple threads on here, but if I remember correctly the 87 model year trucks were the last of the 6.9 and also the first year that the 5-speed was available right? Therefore, did Ford use a unique flywheel for this year or was it the same DMF used on the later 7.3 trucks? I've also crossed clutch numbers between my 87' and slightly newer trucks on Napa and found them to share the same part number. I've got time to sort it out for now...but the sooner I know the better.