1998 4.0 manual transmission question/advice

[drivenyam]

Ok fellas. So I bought my son a 1998 4.0 with a 5 speed manual and 4x4. So it has had some noise coming from the tranny/clutch since getting the truck. Since the noise is when the trucks in neutral and based on engine speed, I was guessing input shaft. Now, 2 weeks ago the tranny stops putting power out and we had to tow the truck home.

So we got the transmission out and there seems to be excessive play in the input shaft. So I am guessing input bearing obviously needs replacing, but doe I need to replace the input shaft itself too? The clutch also appears to be toast, and I am confident in saying that as I have messed with clutches before. Just curious what you guys thought on the input shaft. Is there supposed to be ANY play? Could the input shaft be toast too? Thoughts?

 

[drivenyam]

I have a video of the input shaft play, but can't upload bc it's too large. Ugh. Sorry guys.

 

[RonD]

I know its a little late since trans is out but you could have tested if 4th gear worked to see if it was an input shaft issue
4th gear is direct input shaft to output shaft connection, 1:1 ratio, it doesn't use input shaft gear or the counter shaft gears

But looking at the pictures the input shaft gear and counter shaft gears look fine

So I would say you were having a clutch issue

The input shaft is supported at the end by the pilot bearing and crank shaft so it needs to have a little play so it can align to the end support
It is a judgement call on your part, I don't think there is an exact metric like 1/2" play or 1/4" play that can be used

If transmission was making a noise and ATF level was full then most likely there is an issue inside
All the gears look good so replacing the bearings and synchros shouldn't be too expensive

Input shaft is $50-$60 and it was a part that failed, the gear part of it, but a rare failure

 

[19Walt93]

I'd drain the transmission fluid and if it isn't full of metal particles, fill it back up, replace the clutch, and reinstall the transmission. The early Toyo Kogo transmissions had some problems and the Mitsubishis were worse. I believe yours is a Mazda transmission and we had no trouble with them. While your under there. drain and refill the transfercase, too. It calls for Mercon which Ford only sells as transfer case fluid for a stupid price, most oil companies still sell mercon for reasonable.

 

[drivenyam]

Yes, there was definitely an issue with the clutch. The spline part in the middle of the clutch disc, spins freely. So therefore it couldn't have been applying any power. So I know the clutch is going to be replaced and should get us back on the road, I am just a little concerned about the amount of play in the input shaft. I will try to take pictures to see if I can measure just how much play there is, but it seems like a lot in my personal opinion. But again, I am no transmission expert. I've only ever rebuilt one transmission and that was in a classroom setting. Lol

 

[drivenyam]

Okay so I tried my best without a video to show you the play. The one without my finger is how it just sits in there regularly and then the one with my finger in the picture is me pulling up on it. Hopefully this gives you guys a good idea of how much play is in there. Again I really appreciate you are knowledge and advice.

 

[19Walt93]

There isn't a spec for that movement. The trans uses tapered roller bearings and has end play so some movement is normal and necessary. That's why there's a pilot bearing in the end of the crank to support the input shaft.

 

[drivenyam]

Ok fellas. So we got the clutch replaced and it went well for about 2 weeks. I think the cheap rockauto clutch set I think bit me and the slave cylinder shot out the line. Thank goodness he made it home before it did.

Now, we have replaced it with a Lūk self-adjusting clutch pressure plate and a Lūk slave cylinder. BUT, when I let off the clutch pedal I am hearing a rattle. I have not driven it bc I am worried. What am I missing? Do I need to pump the pedal to get the self-adjusting pressure plate to properly adjust? I am so frustrated. I have done this before and NEVER had these issues. Can anyone make any suggestions? Thank you guys.

 

[BlackBII]

If the rattle only happens when you let off the clutch then I would assume the clutch, release bearing and slave are all working fine, and it's the transmission that's making noise since it will be spinning in neutral with the clutch engaged

 

[drivenyam]

I hear you, but I really do feel like the rattle sounds like it's out of the bell housing area. Could that be the input shaft rattling?

 

[BlackBII]

Hmm does the rattle stop the second you start pushing in the clutch or does it take a second to die down? If it's the input shaft I would expect it to make noise as it slows down. There's not really much there to rattle though as far as the input shaft goes.

Perhaps a loose bolt on the pressure plate?

 

[drivenyam]

I will check the noise tomorrow again and when it stops. I don't think it's a loose bolt only bc we used a torque wrench to ensure they were properly tightened. Thank you for the response and I will check the noise in the morning.

 

[drivenyam]

Ok, so I had a good chance to get out to the truck today. There is a slight rattle(wouldnt notice if I wasnt trying to hear EVERYTHING right now) when it is in neutral whether the clutch is engaged or not. The rattle is worse(something I would say is not normal when clutch disengaged(pedal down) and the in 1st gear. There is no excess noise when I actually drive it. The gear changes feel good, but feel like the clutch grabs hard on downshifting to 2nd(slowing to turn). Thoughts? I have a video of the sound, but cant load it here. I was thinking about posting in a Ranger group on FB.

 

[holyford86]

I've got a couple m5od transmissions in my trucks and both have a rattle sound while in neutral, clutch out, at idle, I've always thought of it as normal, just the backlash in the gears making noise, I wouldn't worry too much. The inside of that trans looks really nice and pretty clean. Initially when reading your post it sounded like a transfer case failure, I've had a couple break the oil pump pickup tube and burn one side of the range selector fork off making it slide into neutral. It doesn't sound like that's the issue in your case though. I've seen input shafts with much more play than that one has and they drive fine.

 

[drivenyam]

I hear you. I have let him drive it a couple of days now. Only on side roads and nothing too far. No issues since though. Kind of sounds like the same noise we had for the year before the clutch gave out. So I kind of went with your theory that maybe it just has some rattle to it.