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I have a 78 f250 with a 351M and 4 speed t18 transmission. I am having trouble driving her on the interstate because of a lack of an OD and my factory gears (turning too many RPMs). I am looking for options to increase my MPH range?
Has anyone done a trans swap to a ZF5 or a NV4500? Do you think this would be a good option in order to keep the same gears but have a OD for the interstate?
Also, I will be stripping her down to the frame soon and I would have plenty of room to work on a trans swap.
The NV and ZF have been done in these trucks. The NV sounds like a easier swap if you're keeping the 351M/400. TMyer has a kit for the ZF also.
I am doing a ZF & 460 swap right now in my 78 but a lot of people do the NV swap.
My thoughts on the gear vendors is that all said and done it on paper its less expensive to do a NV/ZF swap if you find a good trans for the right price. Regardless you need new driveshafts so add that cost in.
If you do the ZF swap look at this link ZF5 adapter kit
I moved my trans crossmember back about 4.5 inches. Then got a pre-blead clutch master cylinder kit from rock auto. Mounted it on the outside of the brake M/C and drilled a hole through the clutch pedal. Put a grade 8 6" bolt in it with spacers to get the pushrod straight and tried it out. Then welded a pedal stop to the floor to prevent over travel. I just need to measure driveshafts and order them next along with a lot of other stuff that isn't related to the trans swap. I kept the BW T-case also. I don't do crazy off roading, the BW is alittle more quiet and runs cooler.
Theres a guy whose local and all his dents have a NV in them. He swears by that swap.
Taller and skinnier tires would help, but you look to not have much more room. Other than that, gear change time.
When is the last time you did a basic tune up? Plugs, plug wires, PVC valve, dizzy cap and rotor bug? X2 on that removing that deer killer heavy looking bumper. Espicially since you have a bed net gate.
Taller and skinnier tires would help, but you look to not have much more room. Other than that, gear change time.
When is the last time you did a basic tune up? Plugs, plug wires, PVC valve, dizzy cap and rotor bug? X2 on that removing that deer killer heavy looking bumper. Espicially since you have a bed net gate.
Recently rebuilt then engine. I think it has 2k miles on it as of now. Also checked dizzy cap, rotor bug and rebuilt the rear drum brakes. This was a farm truck and the bumper was hand made to push cows out of the way
I will be adding 35s and a 4 in suspension lift so that makes me question replacing the 4.10 gears with any smaller gears
The NV and ZF have been done in these trucks. The NV sounds like a easier swap if you're keeping the 351M/400. TMyer has a kit for the ZF also.
I am doing a ZF & 460 swap right now in my 78 but a lot of people do the NV swap.
My thoughts on the gear vendors is that all said and done it on paper its less expensive to do a NV/ZF swap if you find a good trans for the right price. Regardless you need new driveshafts so add that cost in.
If you do the ZF swap look at this link ZF5 adapter kit
I moved my trans crossmember back about 4.5 inches. Then got a pre-blead clutch master cylinder kit from rock auto. Mounted it on the outside of the brake M/C and drilled a hole through the clutch pedal. Put a grade 8 6" bolt in it with spacers to get the pushrod straight and tried it out. Then welded a pedal stop to the floor to prevent over travel. I just need to measure driveshafts and order them next along with a lot of other stuff that isn't related to the trans swap. I kept the BW T-case also. I don't do crazy off roading, the BW is alittle more quiet and runs cooler.
Theres a guy whose local and all his dents have a NV in them. He swears by that swap.
Do you recommended using a ZF or a NV trans for my 351M. I wish it was a 460 but I've already re-built it and added some fast goodies.
Cruising RPM w/o overdrive will be higher yet many of these trucks were run that way for many years. With a healthy engine I think running up to around 3200 or 3300 is OK. My 4.10 equipped '78 with 31" tires gets run at 70 pretty regularly.
Also a good idea to check the speedometer, especially if running bigger than stock tires. When the spedo says "65" for example you may be actually running 75 true MPH.
Vehicle weight
Rolling resistance
Aerodynamics
Mechanical efficiency (trans and rear end gear) vs parasitic losses
Engine efficiency
Engine HP and TQ vs RPM...
Traffic/roadway conditions
Just to build on HIO's comment... pushing these trucks at higher speeds takes some HP. They are not very aerodynamic, especially with an added cow catcher up front.
The engine needs to spin decent RPM to make the HP. Overdrive or at least too much overdrive can put the engine in deep lug which is hard on it over time and may reduce both performance and economy. With 34" tires and 4.10's I don't think I would want any overdrive.
Just to build on HIO's comment... pushing these trucks at higher speeds takes some HP. They are not very aerodynamic, especially with an added cow catcher up front.
The engine needs to spin decent RPM to make the HP. Overdrive or at least too much overdrive can put the engine in deep lug which is hard on it over time and may reduce both performance and economy. With 34" tires and 4.10's I don't think I would want any overdrive.
I have recently rebuilt the engine and it should have around 400 hp ( bigger cam, long tube headers, 4 barrel, bigger intake, block was bored 30 over, ETC)
so HP shouldnt be an issue. Right now with 33s and 4.10 gears she will do 65 with the RPMs fairly high. I don't know what the RPMs are just yet because I havent installed a tach. Installing a tach is next on my list.
Sounds like a really nice engine build. Did you use TM Meyer parts?
Agree good idea to get a tach and also check your speedo. It should be able to cruise at 75 true MPH easy I think with that combo.
I am comfortable at 70 or a bit more with my 4.10/31" combo.
The other thing that has an impact is noise. My bigger than stock but stock type muffler is pretty quiet. No big bellow when she is spinning on the highway.
09-07-2016, 10:44 AM
