4wd system

[furyous66]

I recently have aquired a farm restored 77 m880 i was curious to know if i can swap the transfer case out to one with 2 high or disconnect the driveshaft for summer also im considering a motor swap cause tha t low compression 318 is a gutless pig even with having 4:10 gearing

 

[N1265]

You can swap out the TC, but if you are doing so to save gas you wont notice much differnce unless you also convert the hubs to PT4WD

The TC in these trucks throw the power to the axle with least resistance, therefore if you drop the drive shaft the truck wont move unless you put the TC in HI or LOW LOCK. when in the lock position you should keep the speed below ( I think ) 40 MPH The full Time 4WD system has it's good points and bad points, but remember , it was designed to be used as a "system " to start removing parts or replacing parts with another system won't gain you much of anything in this case.

That being said, many people have converted these trucks to a PT4WD by swaping out the TC AND the front axle. Mile Maker also makes a conversion kit for the hubs, but from what I have heard, they do not save enough money in gas to justify the cost of the kit.



My 318 is a beast, it can turn low 9s in the 3/4 mile,

 

[Elwenil]

Be aware that the NP203 full time 4WD transfer case will NOT swap with any other common Dodge transfer case without modification tot he transmission. The adaptor housing and tailshaft are both a different length than the more common transmissions that mate to part time transfer cases. In order to swap the tailshaft of the 727 you must completely disassemble the transmission as it all comes out the front and the tailshaft is one of the final parts to come out. The tailshaft spline is the same as the later NP205, NP208 and NP241 part time transfer cases but the length is wrong. Complete part time 4WD conversion will require doing the Milemarker conversion to the transfer case AND front axle or the transmission modifications I listed above, the transfer case and drive shafts form a similar donor truck, and either a complete front axle swap or at least a swap from the knuckles out to allow the use of locking hubs which will also gain you a much stronger wheel bearing setup. With that said, there isn't much to gain from the conversion unless you really like the idea of part time 4WD. You will have to drive a lot for a long time to recoup any of your investment in gas mileage alone. Whatever you do, do not just unbolt the front driveshaft and run the transfer case in lock to try and save some gas as you will eventually wear out the differential lock pins and the differential will fly apart.

 

[Rich Johnson]

Ok, so the 882 Im looking at buying, the guy takes the front drive shaft off unless he is going off roading. I noticed that he is driving it in HI LOCK. Now I know why. Has he done any damage to the trucks drive train by doing this?

 

[Elwenil]

Most likely. For some reason people think that removing the front shaft somehow eliminates the drag from the front axle. Unless a hub conversion has been done, the axle is still fully engaged. To make it even more senseless those that have done the full part time conversion report very little if any change in mileage so there is not much point in doing either to a fulltime 4WD truck. In the case of one run without the front shaft and in LOC, the center differential lock pins are generally worn and can eventually fail. How badly they are damaged depends a lot on how hard the guy was on the truck while it was locked without the front shaft.

 

[Rich Johnson]

So where are these lock pins and can they be checked?

 

[ida34]

They are inside the transfer case so basically any checking would be during a full tear down. Put the drive shaft back in and drive it looking for any unusually vibration or noises. Get off pavement and check low, low lock, and high lock also. If everything sounds OK with no vibration you should be OK.

 

[Ruppster]

I have played with many Dodge trucks from the mid 70's with the full time AWD set-up and while I have not driven with the transfer case in Loc mode and the front drive shaft removed I have had a few friends do it and they never had a problem. I have seen problems caused by friends that forgot it was in Loc mode while they still had a front driveshaft installed (i.e. driving in 4 wheel Loc while on the road). While it is possible to drive with the front driveshaft removed and the transfer case in Loc as mentioned there is very little to be gained by doing so. A lot of drag is caused by the front axle. The front axle (a Dana 44) is used in both half ton and 3/4 ton Dodge trucks (unless the 3/4 ton had a factory plow, then it would most likely have had a Dana 60). You can either get a complete front axle from a Dodge or a Chevy with a passenger side differential that has locking hubs and swap the complete axle out or you can grab the 3/4 ton (i.e. 8 lugnut) spindles and hubs from a 3/4 ton Dana 44 and swap those parts on to your full time Dana 44 on your Dodge. The nice part with doing just the spindle and hub swap is that you could even use parts from a Ford Dana 44 3/4 ton axle. Either way it will let you have locking hubs to reduce the drag from the front axle.

As far as the transfer case there is no part time 4wd transfer case that will bolt right in place of the NP203. To upgrade the transfer case there are a few different options.


1.) They used to sell a part time 4wd conversion kit for the NP203. Don't know if they still do or not. That would be the most direct method to get rid of the AWD feature if you can still find them.

2.) They sell adapter plates to install an NP205 transfer case on to the 727 transmission in place of the NP203. May have to modifiy both driveshafts with this method, along with finding an NP205 (just look on CraigsList, easy to find). The nice part with the NP205 is it is all gear drive. No chains to stretch like in the NP203.

3.) This option is a little pricey but is my favorite. Instead of getting an adapter to bolt an NP205 to the 727 tranny get an adapter to bolt the NP205 to the front section of the NP203. You keep the low/high box from the NP203 plus get an additional low/high from the NP205. So instead of having a 2:1 low range and a 1:1 high you get a 3rd option; 4:1 low-low range. This is great if you like to do some serious offroading. Will require a custom transfer case mount along with mods to both driveshafts.

4.) The last option is to look for a Mopar 518 tranny with an NP208 transfer case. This is the same TC used in the mid 80's GM CUCV's. The 518 tranny is basically a 727 auto trans with the addition of an overdrive on the end. While this will probably be the cheapest (if you can find the tranny for a good price in a local junkyard) the down side is the NP208 is considered to be worse then the NP203. The NP208 is also chain driven but it has an aluminum case and is not known for holding up well when doing some serious offroading. If you will be on the road 99% of the time with only some slight offroad use then I would look at this option more then the others.

Ruppster

 

[transman]

If you want to go the aluminum case route better choic than a 208 would be an'89 to93 np 241.Still has right side front shaft plus better low range ratio 2.72 vs 2.61 can be custom built to 241DHD specs. these are used behind 94+ diesel trucks .