im doing a 4x4 swap this summer, gonna get the fram sealed and bring everything back from the rusty grave (surface rust thank god). I was wonderin, "what gears will get this truck moving and get good mileage?" im gonna swap in a 302, c6 tranny and currently on my donor 2wd i have 3.27:1 ratio. i'm gonna say their a lil high for moving a truck (and possibly a car trailer). Also thinking about an NP205 t-case also (my brothers 208 crapped out when goin to school so im goin gears).
give me your advice on gears, upgrades or constructive criticism you have.
-I may put a 6" lift and a solid axle under this (more on that AFTER the initial swap)
well, you want the engine running at its peak cruising rpm, at the speed that you run at the most.
So if you want to run the truck at 65 MPH, you want the truck geared so the engine is turnng it's peak cruising RPM at 65 MPH for good gas mileage.
Most of the trucks built in this era were already geared for fuel economy, set at 55MPH.
My 300-I6 with T-18 4 speed, and 2.75:1 rear end ratio, for instance, turns at 1700 rpm at 55mph. At this speed it gets 24 MPG.
At 65, the engine is turning 2000 RPMs and I get 18MPG. A big whopping difference. Why people hate me for driving 55 on the freeway.
In town driving is around 18mpg as well.
So this is something to consider,
Also your 302 is going to need to wind higher than the 300.
It sounds like the 3.27 ratio would be just about right for the best fuel economy with the tranny you have, at around 55 or 60mph. Give or take. Would really suck for pulling and hauling though, IMO. You are always going to compromise one to get the other though. 3.50's would be the middle ground for compromise IMO, for the 302.
Other fuel saving techniques, is putting on fan clutches on trucks that don't have them stock. It frees up HP and can save you 1 to 2 MPG. They also cool better too by design.
Along with a 6 inch lift usually comes larger tires. You are not going to get very good fuel mileage no matter what gears you use with a high profile truck, large tires, and a non-lockup 3 speed automatic. I would concentrate on what you are going to use the truck for.
I can tell you by experience, that I would not go below a 3.50 ratio. I had a 302 with a c6 and 31x10.5 tires, and it was fine on the highway empty and running around town, and was on the ragged edge when trying to tow. Whenever I had to pull someone out of the ditch or get in some other tight situation, I always had to put the transfer case in low range to get any power out of it.
So if you go larger than 31 inch tires, you are going to be in worse shape than I was. So for example if you put 33" tires on it, I would go with a 3.73 gear or something in that neighborhood.
well i was thinking about a 351W, but i gotta work with what i got. what if i build the 302 for a lil more low-end torque? AFR 165cc heads, small cam grind etc... i have 31" tires on my 2wd (i will swap EVERTHING but frame over) so 3.27:1 will be alright with my truck stock height?
Yes, stick with the 3.27 and try it, though I am not sure you can get a 3.27 for the front diff. I would at least try it with the 3.27 in 2wd and see how you like it. If you end up with a 3.50 frontend, you could take the rear driveshaft out(if it will not leak oil) and run on the 3.50's(or whatever the front gears are) and see if you like that. Then you can make a educated decision on what gear would work best and change the front or the rear or both.
Alright, when it warms up a little im gonna pull that frame in the garage and check that dana 44 and frame. how hard would it be to swap gears in a 44? the 9" 3.27:1 might be a little much for stop n go traffic uphill (high school AND college are uphill) so i was thinking a 3.73. but that would decrease my mileage... man sometimes i hate nevada! lol.
-how hard is it to chance seals, bearings, races etc in the 44 TTB?
-gears? how hard would it be to swap?
-most importantly, what year trucks have an NP205 t-case?
-how hard is it to chance seals, bearings, races etc in the 44 TTB?
You have to have some equipment, or run down to the local machine shop who has a press and a bearing seperator.
Quote:
-gears? how hard would it be to swap?
Same as above, plus you have to educate yourself on how to set the mesh and contact pattern of the gears.
Quote:
-most importantly, what year trucks have an NP205 t-case?
I believe these are found in 1979 and down trucks. They are very heavy cast iron. These are sometimes not a direct swap. They will bolt up, but may require changing the driveshaft lengths front and rear, and rigging the shifter linkage to fit.
From what I can tell, you should be able to bolt the 205 to the c6 you have now, it's just the 205 may be shorter or longer than the 208 you probably have, so that will mess up the driveshafts. Also see what kind of output shaft you have. Some have a slip yoke that slides into the transfer case, and some have an external slip yoke with a fixed yoke on the rear driveshaft.
The fixed yoke is ok as long as you keep it greased. What also works good is one of those cheap colored shock boots to go over the joint with wire ties, and keep the dirt out, and the grease in.
With the slip yoke type, you do not have to worry about any of this.
The only answer to getting good fuel mileage and having a 6"lift with big tires is to have 2 trucks. You can't have your cake and eat it too.
Don't forget that big tires are also a LOT heavier and will decrease your mileage even more than just gears alone.
That's strange you would think that ...........I went rom 31x10.5-15s to 33x12.5-15s & increased my mileage w/o changing anything else but the tires ........ I got more miles per tankful with the 33s
That's strange you would think that ...........I went rom 31x10.5-15s to 33x12.5-15s & increased my mileage w/o changing anything else but the tires ........ I got more miles per tankful with the 33s
I don't doubt you did, but that doesn't necessarily mean you got higher MPG overall, or at all:
How did you calculate your mileage before and after? Did you adjust your speedo to read correctly for each tire size? Did you compare the mileage over the same or nearly the same 1000 miles of driving for each size tire?
Your 31s were already a heavier tire than stock. If the 33s weren't that much heavier, the extra height may have overcome the weight diff.
What we are talking about here is "flywheel" or driveline inertia effect. If you put 50 lbs in the bed of the truck, the engine won't know the diff. If you added even 5 lbs to the flywheel, it would be dramatic. The tires are just a little further away from the block, but have a similar effect.
The second calculator here will give you mph/rpm for diff gears, tires etc.
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4x4 + mpg
........ I got more miles per tankful with the 33s 
