Can’t get past 4th gear...45mph

[Omarmartinez33]

So I was driving home from work and the Comanche decided to slow down in the freeway while the rear was making like a popcorn noise. I made it home alright but is this a blown transmission? I filled it up with gas before this and started acting this way. Any ideas? I got a little discouraged but I know this build won’t be easy 

[Eagle]

If the noise was coming from the rear differential, I would start looking at the differential before thae transmission. However, since you just filled up with gas, it could also be water in the gas. A bad load of gas makes the engine sputter and stutter, and that makes the drive train alternate between being loaded and coasting. That might sound like the rear is making noise.

[Marine1Texas]

Since it started after fill up, check your fuel pressure 31 with out vacuum and 38 with. This happen to me years ago, pulled the fuel pump and the hose above the fuel pump in the tank had a small hole in it. It pumped a bit, however mostly went back in to the tank.

 

Now I would think the noise from rear end would be a different issue, unless it was coming from the tail pipe!

 

As Eagle said could be water, just go through the motions first. Check that pressure if it is good then you go from there. how long ago did you change your fuel filter? 

[DirtyComanche]

A gas station here put a tanker load of straight ethanol in their 87 octane tank, then proceeded to sell it as 87.  I'm not sure how a MJ would really run on straight ethanol, but I'm guessing it would be low power and other side effects like afterfires and stuttering.

[DirtyComanche]

Also, a quick way to see if the differential is maybe okay or not is to just pull the fill plug out and stick your finger in the oil, then take a look at the oil colour.  If it's silver, or has metallic flakes in it, then you're definitely going to be pulling the cover.  If it's tar black you might as well pull it and change the oil too.  While you're in there look for chunks, metal, loose parts, broken teeth, etc.

 

Personally I'm betting it's an engine issue (or running issue, not necessarily the engine's fault) that's causing the driveline to shudder (as Eagle said) or maybe the exhaust to bounce more than usual and hit stuff, or the engine is popping and farting.

[Omarmartinez33]

4 hours ago, Eagle said:

If the noise was coming from the rear differential, I would start looking at the differential before thae transmission. However, since you just filled up with gas, it could also be water in the gas. A bad load of gas makes the engine sputter and stutter, and that makes the drive train alternate between being loaded and coasting. That might sound like the rear is making noise.

The rear differential has a pinion seal leak I’m changing it this weekend 

3 hours ago, Noriyori_Kudo said:

Since it started after fill up, check your fuel pressure 31 with out vacuum and 38 with. This happen to me years ago, pulled the fuel pump and the hose above the fuel pump in the tank had a small hole in it. It pumped a bit, however mostly went back in to the tank.

 

Now I would think the noise from rear end would be a different issue, unless it was coming from the tail pipe!

 

As Eagle said could be water, just go through the motions first. Check that pressure if it is good then you go from there. how long ago did you change your fuel filter? 

It might be from the tail pipe and I haven’t I just brought this last month 

27 minutes ago, DirtyComanche said:

Also, a quick way to see if the differential is maybe okay or not is to just pull the fill plug out and stick your finger in the oil, then take a look at the oil colour.  If it's silver, or has metallic flakes in it, then you're definitely going to be pulling the cover.  If it's tar black you might as well pull it and change the oil too.  While you're in there look for chunks, metal, loose parts, broken teeth, etc.

 

Personally I'm betting it's an engine issue (or running issue, not necessarily the engine's fault) that's causing the driveline to shudder (as Eagle said) or maybe the exhaust to bounce more than usual and hit stuff, or the engine is popping and farting.

It’s leaking. Also it never had a running issue maybe a high idle issue when you first turn it on but I will find out this weekend what’s wrong with it