i have a '89 F-250 with a 351 and a c6 tranny. i would like to know if a '94 tranny out of a van will work. The motor and tranny were the same as in my fathers truck 5.8L and an overdrive tranny. The motor out of the van was transplanted into my dad's 94 f250 and we have the spare tranny. Im sure you all have seen my posts on here about gas mileage and would like to know if this is possible. Im 17 and deal alot with vehicles and love drivin my truck, but i want it to get better gas mileage than what it is. Its only getting about 7 mpg in city and 8-9 on the highway. I was told it may have somewhere near 4.56 gears and dont have the money to do the swap to 3.55. I have the spare tranny and have done tranny swaps before. i just want to know if this one will fit and work properly before i go about it. When i do the swap this summer (if able to) I am going to add heads and a high flow cat system with hopefully some flowmasters. I can still hear the motor over the exhaust and i dont like it. (have stock converter and a glasspack, not loud at all). Any input on what kind of converter(s) and exhaust i should do? Any more information you guys need, let me know. will reply daily with any new posts... Thanks guys.

 

The overdrive automatic behind the 5.8 was electronically controlled, so it will require a new engine computer and wiring for the 94 transmission to function properly. That gas mileage is awful. Do you have a lead foot?

 

I drive as conservative as i can. These truck aren't meant to go fast. I know that. I hate the gas mileage in it, but its my truck and i love drivin it. Had other forums asking about what may be wrong. got alot of information out of it, but nothing seemed to help. I have all synthetic fluids, K&N fuel injector preformance kit, a glass pack exhaust with a 3" pipe. Change fuel filter, tranny fluch, fuel system flush from a shop. i dont know what else to do besides the gear swap or the tranny...

 

is your fan clutch working properly?

is that why engine noise is so loud?

 

fan clutch... someone else mentioned this. i dont really know how to tell if it is working properly. Its kind of sounds like an exhaust leak somewhere. But feeling atound the heads when its started, yu can't feel any hot air coming from anywhere. its a hard sound to explain. maybe its just the motor? It has only 31,000 origional miles on it if it matters any.

 

I was also wanting to get a better distributor than the stock one. Does anyone know where i can find one? Also, what will be the best plug and wire combo i can have. Right now i just have the autolite 8mm plug wires and double platnium plugs.

 

get a spun cat converter from magnaflow cost about 60 bucks at the right shop. you can get a catback exhaust from lmc truck for about 240. glass packs will blow out within a couple months and that truck will rumble, real easy to do too takes about hour and a half with a buddy and the right tools.

 

Have you done a tune up recently? your mileage should be better then that. Look at the tag on the door pillar, there is a axle code on there that will tell what ratio you have.

 

I looked at thsi the other day. It says C5 and i was told this meant that I have 4.10 gears. I recently put in autolite double platnium plugs and autolite wires in the truck.

 

Get rid of the platinums. You don't need them and they're a waste of money in that engine. The stock ignition is a GREAT system for up to about 300hp so no need to replace it. I think once you put MOTORCRAFT copper plugs in it the mileage will increase. I had a '92 E150 with a 351w and a OD trans. I made the mistake once of putting the platinum plugs in it.. I lost 3mpg.

 

I second getting rid of the platinum plugs. These trucks do not like them. Use plain copper motorcraft or autolite plugs. An exhaust leak won't affect mileage any. Do you have a new O2 sensor? Pulled your codes? What's your timing set at? Checked for vacuum leaks?

Swapping the tranny will be a big hassle, with the computer swap, and the wiring. I'm not sure if you need to replace the whole harness or if you can splice in the tranny connectors you need.

 

i also agree with dumping the plat plugs.

 

Thanks for the post. Im going to change the plugs this weekend and ill let you know if it improves any. I had checked the timing a few months back because the motor was missing around 3000 rpm in 2nd gear, when i was pulling a trailor. im not sure what its set at because i let a friend of mine set the timing. Anyways, i haven't gotten a new o2 yet. Are these a hard thing to change, or is it just something I can do with basic hand tools? I have checked all the vacuum lines and they all seem to be okay. None were cracked or deteriorating, but thats not to say that any of them are clogged or what not. im not sure how to know really.

The only code that i got when i pullled them was a 33. "EGR valve opening not detected". I removed the green vacuum hose from the EGR and pluged the hose and the connector on the EGR it was on. There were no vacuum to either of these. I applied a hand vacum to the EGR and found that the valve was opening and closing easily. What could be the prob with no vacuum to that hose? A bad sensor?

 

platinum plugs suck, through some autolites or motorcraft plugs in it.

 

- make sure your timing is set to 10* BTDC. I would really advise against letting any friends do anything to your vehicle unless you are 100%... no, 150% sure they know exactly what they are doing.

- O2 sensors are very easy to change and they can affect mileage.

- The EVP sensor is probably shot. Plugging the green hose will also reduce your mileage.