Engine/Transmission (1994 - 1998) Mileage loss

[erempel]

Earlier this winter I lost around 3mpg, I thought maybe it had something to do with blended diesel and never thought too much about it. With spring and the return of straight diesel the mileage has'nt gotten any better and has inf act gotten worse yet. It is up to around 5mpg off now? Seems to run fine and have the same power as it has had since I put a #11 plate and 3k springs in it last summer. Any ideas?



I checked the rubber return line and it does need replaced,(dies after startup if I park it with the nose up) but I see no leaks that are fuel. I have the output shaft seal on the transfer case leaking, which at first I thought was fuel, but that is the only red leak. Also the vacuum pump leaks like a sieve, but that is engine oil, and all the vacuum stuff works fine, so I believe the pump is working OK. Not sure where to start looking.



In the last six months I have put both tie rods on it, the stabilizer bar, an upper ball joint, a wheel bearing, all the brakes, killed the KDP, and now tonight coasting down a hill I lost 5th gear .

So since I now get to tear the back of the transmission off I guess I better look harder for this mileage problem before it bites me.



Could this be a fuel pressure problem? I haven't checked it because I have yet to figure out where and how to check it. The fuel filter has about 10k miles on it, but probably only 5k when it started this. It also appears to be getting steadily worse, and the truck now has 126k miles on it. Any help would be appreciated.

 

[illflem]

Fuel pressure is the first thing to check, low pressure will lower mpgs. It doesn't matter how many miles are on your filter, it can get plugged by one tank of dirty fuel just as easily 10 miles after a change as it can 25k afterwards.

There are a couple of way to check FP. You can buy an adaptor from TST for $25 that adapts your filter outlet bleed screw to 1/8'' pipe thread. Or the easy way, just drill and tap your injection pump inlet banjo bolt to 1/8'' pipe and screw an 1/8'' needle valve into it.

 

[gjacobs]

Do not know if it will help you but it did for me. There is a brass 90 on top of the AFC housing that screws in and turnes into rubber vaccum hose. Mine was loose and had some junk in it. After tightning it up I saw a 3-4 mpg increase.

 

[erempel]

I'll check that fitting and put a new fuel filter in it. I also am going to drill out the banjo fitting for a needle valve, thanks for the ideas.



I got the transmission tore apart tonight and put the nut back on. I red loctited the nut and the pounded the lip of the nut down to the main shaft and then spot welded it to the shaft, anyone ever try that? I just buzzed it and no more than a minute after I welded it I grabbed the nut and main shaft and it was barley luke warm. I was conserned that welding it may temper the shaft but after doing it there is no way it could of tempered it enough to cause a problem. I know of one other guy that did this and has not had any trouble with it, that is really the only reason I decided to actually try it.



Tomorrow night milage problem and leaks.

 

[Dbonzi]

I spot welded nut on as well, been 40000 miles so far and no issues. I was told on here that the shaft will break but, so far so good. Like you I didn't put alot of heat to the shaft and only in a small area, so I don't we will have any problems.

Good luck.



Dennis

 

[KWentling]

I would caution against welding on you're transmission shafts. It WILL cause a stress point. Weather or not it will fail??? I wouldn't do it to mine. I work in a welding/machine shop and have seen numerous shafts (not specifically our transmission shafts) broken where someone has tack welded on them. I don't know the carbon content of our transmission shafts, but the higher the carbon content, the higher the likelyhood of a cold weld causing it to break. Carbon steel shafts can be welded on, but you need to preheat to 450*F or more, depending on the content of the steel. Not something you want to do in the transmission. Hope you don't have a problem with it.



Kim