ford 6.9l 4 speed to a 5 speed zf 5 swap

[mikeproeder]

hi i have a 1984 ford 6.9l diesel i have a 4 speed but its only doin 55 maybe 60 on the freeway i would like to put the zf5 5 speed out of a newer 7.3 idi or powerstroke. does anyone know if the zf5 will bolt up to the 6.9 i know there the same block but i just want to make sure. thanks

[6.9Laska]

id say you have something else wrong if thats all the faster it will go. i also have a 84 6.9 4 speed and it will do 95-100mph and thats with 4:63 gears,

i believe that the zf5 will work in these trucks but i think there is some mods u have todo, im not sure what but im sure someone here knows

[mikeproeder]

that is strange do you have a gearvendors overdrive or somethign because most of the 6.9 people i know do the same as i do

[6.9Laska]

no everything is stock. i know with the c6 auto top speed is 65-75 and that has 1 less gear then the t-19 4 speed. maybe there is a problem with the internal govener in the injection pump that wont let your rpms get high enough just a thought

[RyTaWaY]

I agree with 6.9, my 4 speed begs to go over 65 on level ground even though I try to run 55-60. Infact when i accidentally hit 70 it feels like a turbo kicks in and I barely have my foot on the gas. I have never purposely pushed it past 70. Going uphill is different especially towing anything more than 5000, I run around 40-45 in third up 6 % grades with about 1/2 to 3/4 throttle.

[mikeproeder]

mine is a non turbo but a turbo will only change my rpms a little i know its reving up i dont have a tac but i know what high rps are and its pretty high

[goosefoot33]

I'm with Ry and Laska, I've got a four speed and do most of my driving on the highway and can easily get over 70mph if I'm not careful. Once I get over the 60mph "hump" the throttle seems sensitive in that if I press down just a little it'll start taking off and easily hit 75. Because of this response it seems like I'm almost redlining it. Cruising at ~65, I am at about 3/8 throttle, where are you when you're doing ~60?

[Scoobywagon]

Originally Posted by 6.9Laska

i also have a 84 6.9 4 speed and it will do 95-100mph and thats with 4:63 gears,

Sorry, but that math doesn't work. 4th gear is 1:1 (no overderive). If you've got 4.63 gears, then you need a 48" tire to run 100 mph with an engine rev-limited to 3300 rpm. Which, as I understand it, the 6.9 is.

[Njellison]

Originally Posted by Scoobywagon

Sorry, but that math doesn't work. 4th gear is 1:1 (no overderive). If you've got 4.63 gears, then you need a 48" tire to run 100 mph with an engine rev-limited to 3300 rpm. Which, as I understand it, the 6.9 is.

I think the rev limiter is around 3800 but I cannot be sure exactly where mine limits due to an inaccurate tach. I think the limiter is part of the IP function so there is probably a margin of error inherit it them (+/- 100 rpm?) That said I agree with most posts in that I cannot get near 100 mph with this truck. It's more like 80 mph with no wind, slight downhill, on a good day. Best economy seems to be about 45mph or right around 2200 rpm on my (inaccurate) tach.

[Njellison]

Oh yeah, almost forgot. This swap has been done and there is a detailed write up somewhere in here (on the 7.3 idi maybe) along with pictures showing the mod. If I recall the major changes where:

Stick shift cut out was further back on the floor
clutch was different (dual mass vs single mass ?)
Drive shafts needed mods.

It was mentioned that the guy ended up with a diesel zf5 instead of a gasser as he thought the gear spacing was tighter for the diesel so you might want to check on that.

Final overdrive was not a HUGE reduction but even if final drive is .77 that would move you from about 2600 rpm at 65 down to around 2000 which sounds pretty good to me.

[mikeproeder]

thanks alot everyone !!

[Tat-Tude Dually]

I would like to know about this swap as I have the auto and I would like to make it a 5 speed.

[reymored]

I did this swap. It's fairly easy. Mine was 4wd and required no driveshaft mod. You must use the dual mass flywheel or supposedly there will be problems with vibration in trans. The stock setup uses the DM flywheel. The DM flywheel can be expensive and troublesome I would recommend getting in touch with Luk clutches. They specialize in a DM to SM (solid mass) conversion. I simply purchased the used DM flywheel that came out of the same truck the zf came out of. I chose this route because I knew it would be temporary as my pickup now has a cummins bolted to the zf. I would also recommend using the floor pan out of a pickup with a zf in it. I've heard that the original floor pan can work however with a little beater adjustment. You will not have to make changes to the hydraulic clutch. Simply use a zf clutch fork and throw-out bearing. You will be using the zf clutch setup anyhow. I'm having some difficulty recollecting whether or not the pilot shaft dimensions differ between the two but this should be easy to research. Again, this is not a difficult job in terms of head scratching. I'm fairly certain the zf came standard behind 6.9s in 1987 anyway. I will say however, all things considered I might have been happier with leaving the t-19 and adding a gear-vendors. I chose to use the zf because I believed it would be cheaper as I bought a used transmission. In the long run, I spent about the same. That being said, you will certainly be happy with the results, it is very nice to have the extra gear. Good luck, I will try to keep checking to answer any questions you may have.

[mikeproeder]

thanks alot
ya the first ting that came to mind was gearvendors once i went on the freeway for the first time so if i can find a gearvendors used cheep i would much rather have that but my pockets are not very deep so i usually wate to see what comes along before spending alot of money

[6.9Laska]

6.9 does not govern out at 3300 rpm. more like 3800. so with a stock set up and a 4 speed they will run 100mph and you dont need 48 inch tires