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

[Scoobywagon]

Originally Posted by 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

Still doesn't work. Even at 3900 (assuming a +/- 100rpm margin of error), the truck will top out at 76.18 mph with 33" tires (285/75-R16). At 305/80-R18 (37"), you top out at 86.34 mph. Even if you go to 375/80-R18 (42"), you still top out at 96.58 mph. Now, thats close, probably even within the margin of error of the speedometer, but still not 100 mph.

Ground speed is ultimately governed by wheel speed. So...the question is, what is your wheel speed? The answer is as follows. Maximum engine speed is a known value at 3900 RPM. Also, 4th gear and the rear diff have known values. 1:1 for 4th, 4:63 for the diff. The gear ratios multiply, but, since 4th gear is 1:1, you still have a net gear reduction of 4.63:1. Therefore, your wheels will make one complete revolution per 4.63 revolutions of the engine. So your maximum wheel speed is 3900 / 4.63 = 842.33261339092872570194384449244 rpm at the wheel when the engine is absolutely redlined. How fast is that? Depends on your tire size.

Seems that most of these trucks have tires that are 33" - 35". A 33" tire will have a circumference of 103.14 inches. This is to say that for every revolution of the tire, the truck will travel forward 103.14 inches or 0.0016278409090909090909090909090909 miles. This means the tire will have to turn 61431.064572425828970331588132635 times to clear 100 miles. The tires will need to turn 61,431 times in one hour to attain the required speed. The engine turns 4.63 times as fast as the tires, so the engine will turn 284,426 times in that hour or 4,741 RPM. That's 841 RPM past even the most optimistic projections.

Using the same math, if we go to 4.11 gears, we top out at 85.82 MPH with 285/75-R16 tires. Drop to 3.73 and suddenly we jump all the way up to 94.56 MPH on the same tires.

So I repeat. These trucks will NOT run 100 mph without some assistance in the form of gearing.

[Tat-Tude Dually]

So this one time at band camp...........I got a spoon to do a 100




so anyway what does it cost one to do the tranny swap?

[mikeproeder]

thank you scoobywagon for clearing that up they must have 273's in there rearend and not know it or something

and as for the price i dont know yet because i have not done it yet but i was reading that some one had done it before and a bunch of things need to be changed over and it will end up cousting a lot of money and the best bet is to just do a gearvendors overdrive and just keep the old t 19 tranny

unless that is if you find a crashed truck cheep and pull all the parts out of it that would be the way to do the zf 5 swap and save money

[Scoobywagon]

Originally Posted by Tat-Tude Dually

so anyway what does it cost one to do the tranny swap?

Not sure about pricing where you are, but here, at least, I can get pretty much any trans for about $150 (Pull-A-Part). The clutch is different, which sort of implies that the flywheel is too. Flywheel will set me back about $20 (also Pull-A-Part). Clutch set will run you about $210 at Autozone. Might as well replace all the u-joints, since you've got everything apart ($50 or so depending on which rear shaft you have). So you're up to about $430 in parts. Then there's time. There's no such thing as book time on something like this, but I'd be surprised if you left a shop with less than $1000 for labor.

Frankly, I'd search Craigslist or something and find a wrecked one. Buy it for parts and do the swap yourself.

[dieselkingcoal]

6.9laska is correct. these trucks can run 100 with the 4 speed in them. there is more then one gearing option for the t-19. somebody must not know how to do math very well.

[Scoobywagon]

You're quite right. There are multiple gearing options inside the T19. However, whether you have the close ratio 4-speed or the wide ratio 4-speed, 4th gear is STILL 1:1. 6.9Laska claims to have 4.63 gears in the rear. Feel free to do the math yourself. I'll even help you with it if you want.

[LMJD]

6.9laska is correct. these trucks can run 100 with the 4 speed in them. there is more then one gearing option for the t-19. somebody must not know how to do math very well.

You might want to rethink that one. It doesn't matter what the lower gear ratios are, or how many speeds it is, unless it's an OD transmission high gear in any trans is always 1:1 ratio.

4th gear is STILL 1:1. 6.9Laska claims to have 4.63 gears in the rear.

Right, and 4:63s would be even lower geared than 4:10s. These engines were governed at 3300-3400RPM, 100MPH? I agree, somebody needs a speedometer check.

[6.9Laska]

hey guys im not arguing with the math. the math might show that its not possible but i own the truck and i can tell you that my truck WILL do upto 100mph and the speedometer is dead on (ran side by side with a grand prix and it tops out right at 100). i have rebuilt this truck from the ground up and took the time to make sure everything works correctly. the rearend does have 4:63 gears as i have checked it myself and the web says a axle code 72 is standard diff 11000lb 4:63 readend. tach reads about 4000-4100. maybe govenor is off alittle idk but i see no reason for poeple to knock on others because of what they post as no ones truck is the same.

[Scoobywagon]

It just occured to me. You guys are correct. These trucks WILL run 100....kph. That would be Kilometers Per Hour. Yes. These trucks will DEFINITELY run 62 MPH.

Assuming you meant 100KPH, rather than 100MPH, I apologize.

But they STILL won't run 100MPH. Not without taller gears or taller tires.

[Scoobywagon]

I'm not busting on you, but the math just isn't there for one of these trucks (in more or less stock form) to run 100 miles per hour.

But I'll give you this. with 4.63 gears on 35" tires and running 4100 RPM, you'd be running just a shade over 92 miles per hour. Unless your speedometer has been accurized, i.e. used for police purposes, it is not dead on. Same goes for your friend with the Grand Prix. It can't be because it is mechanically driven and there is some inherent slop in that system. As a rule, most speedometers will indicate a speed slightly higher than your actual speed. I believe this is done for a couple of reasons. First, we Americans like to speed. If the speedometer is just slightly fast, you feel better because you have a fast car. Also, this tends to make your fuel economy numbers look a little better since you've apparently traveled farther. Most speedometers are calibrated to be most accurate at about 60. 100 is well outside that. So at 92 MPH, it is entirely possible that the speedometer indicates 100.

Want to be sure of it? Get out on the road. Run it at 100 indicated and have someone time you between mile posts. 1 mile at 100 miles per hour should take exactly 36 seconds.

[RyTaWaY]

Wasnt Mikes problem that he was running 55-60 max on the freeway? I dont have time to do the math on that too many 909's, but my tach says about 2250 - 2500 at that speed. Well below the governer cut out of 3300 +/-. The math tells me that no matter what kind of tranny he puts in there it will still have a problem.
I guess his truck must have some monster gears for stump pulling.

[Scoobywagon]

If he's got 33" tires and 4.63 gears, he'll top out at 70 MPH at 3300 RPM. Depending on his speedo, I could see it showing 55-60. There's also the question of his speedo drive gear.

[RyTaWaY]

Must have high performance speedo drive gears... If the 5 speed tranny is used with a dual mass clutch which all the mechanics I have talked to say is garbage ... What about the newer 6 speed dodge manual tranny. Does anyone know about that retrofit???

[mikeproeder]

Originally Posted by RyTaWaY

What about the newer 6 speed dodge manual tranny. Does anyone know about that retrofit???

that would be cool ill look into it

[B-rad]

What about the ZF6, the Fords 6 speed. I would look into that before the Dodge transmission. I guess I just like keeping it all Ford.