I've been thinking about swapping in a ZF 5 speed into my truck so I can get the OD gear. I figure this would probably be way cheaper than an OD kit which I had looked at for my last truck(92 F-250, 460 with C6 auto). I'm 20 miles out of the main town and would really like to have OD to help my mileage. With the way I drive anything helps, haha. So I figured if I could pick up a parts truck 87-91 regular cab longbox like mine, then I should be able to just swap the parts right? I'm assuming that I'd need to swap the T-case too(not sure whats in the 87-91s, BW? NP?) Any help would be great, thanks in advance!!

 

it all should bolt in. u can mount ur tcase behind the zf, but i do belive the drivshafts are different. but dont qoute me about that.

 

My NP208 will bolt the the ZF? And if the driveshafts are different what would I need to do about that?

 

Driveshaft length would be the only concern, yes your current transfer case will bolt up to the zf as long as said zf is from either a 4x4 or F-SuperDuty ( the superduty had a driveline brake which can be removed and a transfercase mounted in it's spot) if it's from a standard 2wd truck then the output shaft will have to be changed. I do believe that the ZF is longer than a T19 but I could be wrong.

 

Just so I understand correctly, my t-case would bolt up the the ZF no problem, and if the ZF is longer, I would just need to have my driveshafts lengthened? What about using the ones out of the parts truck? Or would they not work with my D44 front/D60 rear since the 87+ got D50/Sterling 10.25?

 

If you install the ZF and use your 208 t-case you can reuse your original driveshafts. The t-case linkage will adapt to the pivot point on the ZF and work like it should. The mounting point for the ZF is a tad further back so you will have to drill new holes in the frame for the crossmember. You should grab the shifter floor section as well since I believe it is raised to clear the ZF. Make sure the ZF you get comes from an 4wd IDI truck, an OBS PSD ZF should work as well but no gasser tranny will fit.

 

D50 was for super and crew cab, regular cab still had D44... I thought that the 85 F250 used the sterling rear just like mine. I think that the ZF is longer, but I don't have a T19 to compare mine to.

 

A D50 could be ordered under a regular cab truck, but it wasn't standard like it was on the supercab trucks.

I too think the ZF is a tad longer, but not much. I have done a ZF swap but I was ditching a C6. I did however read a good thread on FTE from a gentleman who did this exact swap and said he was able to reuse everything by just swapping the ZF and keeping the old t-case.

When I did my swap, I replaced my C6/208 with a ZF/1356 combo. I reused my original front driveshaft but had to use the rear shaft from the donor truck as the 1356 has a slipyoke instead of the 208's fixed yoke.

 

@Sycostang67
Would the front driveshaft still be long enough to reach with the longer zf?

@rjjp
I may be wrong, and I have no problem admitting when I am, but I'm pretty sure they went to the Sterling rear in 87. Another thing I just thought of is the clutch. What would I have to do about that?

My step dad's a mechanic and I ran the idea by him and he said that he wasn't sure about the clutch because he thought mine was mechanical and the zf was hydraulic. Anything I need to worry about there? Also, he's not real knowledgeable on Fords as he's a Chevy guy. Thanks for all the help guys. I really appreciate it!!

 

Yeah, you can reuse both driveshafts if you keep the current NP208 transfer case.

The sterling made it's appearance in mid 1985, I have an 85 F-250 and an 86 F-250 both with the sterling rear axle.

The hydraulic clutch started in 1984 sometime, so your truck should be hydraulic.

Another thing you have to consider is the flywheel. The ZF equipped trucks came with a dual mass flywheel, basically a 2 piece unit designed to smooth out shifting and reduce vibrations and gear noise in the transmission. Your truck currently has a single mass flywheel, similar to a gasser. The problem with the DMF is the springs in them tend to break or wear out and eventually will spin not letting you move. A new DMF is expensive, sometimes $1000. I believe NAPA sells a single mass conversion kit that will come with a new flywheel and clutch assembly for less than $500. The only real drawback to going with a SMF is the transmission may be a tad noisier. Some people will overfill the trans fluid a bit to help quiet it down, while other people have claimed no change in noise from a SMF conversion.