hello i need help on deciding what is the best engine and tranny for my 1979 gmc k2500 i know hardly anything bout diesels and dont know whether a 12 valve cummins or a detroit diesel is better any advice

 

hard to beat a 12v

 

12-valve... Several reasons, beyond just reliability and reputation. Lots of parts available. Any good Diesel shop, and nearly all bad ones can fix it.

If you want a drawback, there might be a couple, and they may not even matter to you. The 5.9L Cummins "B" engine weighs a lot, like 1100 lb., so you might need a bit of beefing to carry it around. Also, they generate a lot (comparatively speaking) of torque, so if you get real ambitious with power output, you'll break stuff behind it.

 

ok well thats good to know i have always been a cummins fan so that helps my only draw back is i have heard both the NV4500 5 speed is a good tranny it has trouble between 4th and 5th gear and that the NV5600 is a better tranny to go with and not only that but that with the six speed i get more torque i am not sure what the difference is please help

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also would a stock set of one ton suspension for that year of chevy handle it or would i need to beef up the frame also

 

You may have to beef it up a little, maybe air shocks. The stock motor in that truck is several hundred pounds lighter. As for.the.Tranny, the nv4500 in my opinion is the best manual Tranny ever made. Only problem is the 5th gear nut backs off. Pull the tail housing and its right on the output shaft. Can replace it or just put a tack weld or ping the threads to keep it on. The reason I prefer it over the 6 speeds is it shifts so much smoother and faster. Seems like the synchros on the 6 speeds take forever to line it up.

 

Son loves the 4500 in his RamCharger.... I've read some guys (pickups, not SUVs) complaining that really heavy towing is hard. There's a big RPM gap (I don't remember if it's the 2-3 shift, or the 3-4 shift) that makes life difficult.... HOWEVER, there's a way around that, too! A governor-spring kit gets you more RPMs to play with before defueling. That way, you can hold a lower gear up to a faster road-speed before upshifting. Even with him not using the R/C as a tow vehicle, he likes the additional RPM. Keeps the low-rpm vibrations down. That 5th-gear nut backing off is often blamed on "lugging" the engine. below 1800rpm, the combination of vibrations and torque treats that nut as though it was being impact-wrenched.

 

You want the cummins. There's a reason you don't see old Detroits much.

 

Yeah. Don't be "that guy"^^^^^^

 

Hey hey hey know

 

if you are doing a 4x4 this is the only repair that works then the transfer case helps hold the nut in place
NV4500 Transmission 5th Gear Repair