Front wheel drive and rear brakes?

[NitroNick]

Decided to take my 25 out today and before I was halfway through tank one I noticed I only had front wheel drive. I recently changed out all of the driveshafts with MIP so I first made sure everything was still tight in that category and then I thought it could be the spider gears in the rear?

However when I turn one wheel the other still rotates in the opposite direction so that seems normal.

What is weird is when I turn one rear wheel and hold the other three there is a grinding noise, but since the rear center shaft is turning and the diff seems to behave normally I feel like the problem is in the transmission, what do you guys think?

Also when rotating one rear wheel the spur does not spin but does for the front wheels.

 

[olds97_lss]

Sounds like the rear diff. The trans is solid axle inside, so if you spin the front tires and the rear trans cup spins, then the trans is likely ok.

 

[Biddie_fiddler]

Sounds to me like the pinion and spur gear on the diff, image below for reference

 

[NitroNick]

Sounds like the rear diff. The trans is solid axle inside, so if you spin the front tires and the rear trans cup spins, then the trans is likely ok.

Rear trans does not spin, only front drivehsaft spins, that is why I think it is the input shaft on the trans. When I spin the rear wheels I can spin the brakes, but there is no movement in the front half of the truck lol, the 25 is old, I guess the shaft has had enough

 

[Biddie_fiddler]

Sounds weird, but with my flux I was snapping the pins that hold the cups in place on the trans. You know those allen head screws with a long pin.. Dunno what to call them ?

Although this doesn't cause gear crunching...

Try spinning your spur gear by hand and hear for any weird sounds. Would recommend checking diffs tho. The trans in these things are very hard to break, most of the time its the diffs that blow out first

 

[NitroNick]

Hmmmm I will have to take a closer look, I'll try spinning the spur and see what happens. Yeah, I mean I have to take the entire truck apart to get to the trans so I might as well check the diffs lol.

Ok so I spun the spur and only the front wheels spin forward. There rear center shaft does not spin at all, again even if my rear diff was out this would still spin so that is why I don't think it's my rear diff and is the input shaft. At the end of the day I guess I just have to take it apart and see.

 

[olds97_lss]

Oh, thought I read that the center shaft spun. I'm not sure how the MIP's are installed on that. Guessing one end is a bone and the other is a cvd joint. If spinning the front tires spins the spur and spinning the rear tires spins the rear shaft but not the trans, then odds are it's the set screw pin in the brake hub has fallen out or broken off. So the hub just spins on the shaft.

 

[NitroNick]

Ohhhhh ok now I see what you're saying, I'll check that out!

 

[NitroNick]

You guys were right, I just checked the truck and the pin is missing! Crazy, glad it's not the trans lol, Ill have to loctite that down this time, never had that happen to me before

 

[olds97_lss]

I have those fall out/break off quite a bit. Seems to happen more on the diff input side though vs the brake hub.

 

[Biddie_fiddler]

I have those fall out/break off quite a bit. Seems to happen more on the diff input side though vs the brake hub.

Interesting, mine always break on the trans side

@NitroNick I'm glad the investigation into your mysterious front wheel drive case has been solved!