Zf5 Swap for an 86 6.9 idi

[Aron]

Well since my trans had to come out due to the bellhousing shattering, I was wondering what all needs to happen to zf5 swap my truck.
(Apologies if this has been asked before)

[Gary Lewis]

It has been asked several times, but the answer is simple enough that we've not bothered to put it on a page.

Obviously you need the correct ZF5 for the IDI.  And you'll need a new clutch as the input shaft on the ZF is a lot larger than that of the other transmissions.  Plus you need the transmission cover as the ZF is taller.  And you need the right engine plate or block plate as the ZF has an angled opening at the flywheel.

Then there's the crossmember.  It is best to get the correct ZF crossmember, but I've reused the one from the old transmission.  In that case you'll have to drill new holes in the frame at roughly 1" farther back for the crossmember itself.  And if you don't have the right gussets you can get by with the old ones by bolting them in top and bottom and then tightening the bolts up and flexing the gussets.

[Aron]

Huh...That's gonna put the truck off the road for a while, and its a lot of work/part searching. Maybe I'll just deal with the 55mph and 2500rpm engine for right now, thanks for the help

[Gary Lewis]

Yes, it takes a lot of searching.  And frequently the ZF5's need to be rebuilt, and that can be expensive.  So it might be better to live with the existing tranny.

[Ford F834]

Clutch/Flywheel: there used to be a 6 bolt ZF clutch that fit the 4-speed solid flywheel, but it has not been in production for many years. Buy a 8 bolt flywheel and clutch for a naturally aspirated 7.3 IDI. The balance will work on a 6.9. Single mass conversion flywheel and clutch kits are fairly reasonable.

Transmission: IDI ZF’s are close ratio, but you can use a wide ratio 460 ZF if you re-drill the holes on the bellhousing. Not everyone is keen on this procedure, but it is commonly done by owners wanting the wide ratio or if you can’t find a diesel ZF.

Inspection plate: try to get this with the transmission… but if you don’t you can run without it until you find one. Unlike the 460, the IDI inspection cover is not sandwiched between the engine and transmission and comes off with a couple bolts from underneath.

Cross member: if you can get the ZF cross member it will directly bolt in the original location. If you don’t get the cross member, you can use the 4 speed one but it will have to be moved back a couple inches and new holes drilled.

Tunnel cover: the ZF is taller. If you can’t get the actual ZF cover, note that any cover from 1988-1996 F-series are the same shape and you can cut a hole for the ZF shifter.

[Gary Lewis]

Thanks, Jonathan!  Very good info.