Jump to content

Transmission Taking a Dump


Huntin720

Recommended Posts

Got in the truck the other day and headed down the road. Right as I shifted into 3rd there was a horendous crunch. Then everything was fine. So I drove it and it was fine for a while. But it's happened a few more times. Today 2nd gear is also doing it. At first it was just as I let off the clutch so I thought maybe sinchros, but now it's pretty much any time I put any load on it in either 2nd or 3rd gear. 1,4,5 are all running fine.

 

I checked fluid and it was full but really dark. I figure it was whistling past the graveyard but I drained and refilled it any way. Now it shifts very smoothly. Really nice. OF course the crunch is way worse and clearly not going anywhere. Also there was a fair amount of metal chunks in the drained fluid.

 

So it's probably about time to start looking for a gently used 5 speed for a 1980 720 4x4 in or around the Portland area. And hopefully one that's cheap. I'm broke as a joke.

 

I know I can swap it out because "they" tell me that it's not that complicated and to "stop being a pussy". I'm pretty sure that a full tear down and rebuild of the one I have is not so much in my wheelhouse.

 

So what am I looking for, where should I look and how should I go about it.

 

Also am I missing some miracle cure or simple solution that is obvious to guys that know what they are doing?

Link to comment
  • Replies 42
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Quit driving it, you likely lost the clustergear bearing, if you can put a new bearing in it before the thing self destructs, it will likely be the cost of the bearing and gear oil.

being it's a 4X4, it will be harder to get the transmission out, but if you destroy the transmission, it will be way more expensive.

  • Like 1
Link to comment

Yes you have to pull the transmission out, and then pull it apart.

The clustergear/countershaft bearing is the lower bearing in the front of the transmission, I am not saying that it is the issue, but it is sounding like the issue.

OK, when the engine is running in neutral in your driveway with the clutch pedal not pushed in, does it make noise?

When the engine is running, and you push the clutch pedal in and put it in gear, does the noise go away?

Link to comment

Yes.. if you know what your doing and have the tools afternoon.. otherwise a long long time. 5speeds are simple.. but not if it's the first time working on one.

 

Probably best to just swap it out unless you have someone that can help you.

  • Like 1
Link to comment

Here is an article about how to pull a transmission apart, I wrote it to tell people how to make a shortshaft 5 speed for a 521, but it applies here to pulling one apart.

http://community.ratsun.net/topic/28473-how-to-put-together-a-shortshaft-5-speed-for-a-l20b/

Here is a photo of a clustergear bearing going out on my 521 work truck, see how one of the bearings appears to be missing.

 

DSCN3966.JPG

Link to comment

I don't know that it is the issue, sometimes they don't make noise at all and self destruct, other times they give you plenty of warning.

Here is a photo of one that came apart, it ruined the front cover and case, this one has not been fixed yet, it's just sitting in my garage waiting for a bearing and front cover.

DSCN0715.JPG

If you found metal chunks in your transmission when you emptied the fluids, it's one of the bearings, it's usually that front lower one, but my friend down the road lost the one in the back, that one required pulling the gears off, and recently someone else lost the main upper bearing, that one is a little harder to deal with.

There was a guy back east in New York that kept driving his truck, he lost the counter shaft, it broke, he had to find another transmission.

  • Like 1
Link to comment

That one didn't ruin the case, but the front steel cover was destroyed, that's what happens if you keep driving it, eventually something is going to give up.

A 4X4 is a bitch, you might be able to drop the transmission without pulling the transfer case, I don't know for sure though.

I am hard on transmissions, I have fixed a lot of them, I would even help you out with it, if you were to bring it over(the transmission), we could pull it apart and maybe fix it.

  • Like 5
Link to comment

He more than likely has a longshaft 4 or 5 speed, it has this really short driveline between the transmission and the transfer case, but it will unbolt off the transfer case, and then can be pulled out of the back of the transmission, but I don't know this for sure, if it can be removed, then I think there would be enough room to remove the transmission, but I have never done it before, so there may be other issues with the 4X4 that I don't know about.

The 1980 4X4 came with 460 something gears, not a high speed truck on the hiway, but it will pull stumps out of the ground.

  • Like 1
Link to comment

All the kingcab 2wd 720s have a longshaft in them, fact is all 1980-82 Datsun trucks have longshafts in them, so do the 1980-82 4wd 720s, but the 4wd transmissions do not have a speedo drive in them.

After 82/83 they started putting short shaft 5 speeds in all the 4wd trucks, and in 85/86 regular cab/short box trucks, since you have a 4wd, you can use any longshaft you can find, and you could use the short shaft transmissions also if you grab the longer driveline that goes between the tranny and transfer case.

Early Z cars also have the longshaft transmission you need, you would have to ask someone like Dmike what years will work for your truck.

The Datsun 620 has longshaft 5 speeds also, but the gearing is different in a lot of them, another thing that Dmike could shed some light on.

Ok so when I'm looking for a longshaft 5speed, what are the options? What years and vehicles should I be looking for?

  • Like 2
Link to comment

Awesome. I couldn't get a good pic today with it where it is and I have a few days before I can even think about taking it apart. But I did measure it and it's the 31.5". Also it looks like it's wired with three switches. All of which are disconnected on mine.

  • Like 1
Link to comment

I suppose I should have wrote in my last post that any longshaft/shortshaft from a 720 other than the 1980 will need the front case changed out, but as long as your case is not damaged, it's not that big of a deal, I posted that link on how to remove the case, depending on the year the donor transmission comes from, you might also need to change the front clustergear bearing, but that one might be bad already, until you remove the transmission, you will not know what is wrong for sure.

I live in Vancouver WA, across the river from you, if you need help with the transmission. :)

  • Like 2
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.