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1987 D21 5-speed


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Hello, Brand new here, Thanks!, I'm in the middle of a input shaft bearing replacement. I've got the old bearing off

and now I'm not sure if I should try and put the new bearing on without separating the transmission or if it's even possible. One more thing, the input shaft came out while removing the bearing, I might be in over my head! any help would be great, Thanks, Jeff 

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The input shaft with the main drive gear on it cannot come out before the counter bearing below it is removed and the counter drive gear behind it. The counter drive gear blocks the input shaft from moving forward. The counter drive gear is removed with a puller and at the same time the main drive gear will come out with it.

 

 

620CAFS5W71B85turbo200sx019Large.jpg

 

Input shaft and drive gear top, counter bearing and gear below it. See the 4th brass synchro ring? That toothed part just forward of it won't pass the counter gear below it. .

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I didn't know that it was possible to remove the input shaft without removing the cluster gear shaft.

Why did you tear into the transmission, did it quit working, was it making a bunch of noise?

I wrote this article in the link below about how to make a short shaft transmission for a 521, it describes how to remove the front case, you are going to need to remove the front case to inspect for major damage, it's not that hard to do.

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

I have a feeling that you have major damage in there, you are welcome to come to my house if you want help pulling it apart, I have done it lots of times, although I have never completely pulled one apart to rebuild it, I have just replaced front bearings and changed front cases.

Do you have a clear photo of the bearing area?

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If the input shaft is out then you must have the front case off and mean separating the tail shaft from the adapter plate? No it doesn't need to come apart to get at the main and counter bearings. Almost always it's the lower or counter bearing that makes all the noise, as it is subjected to severe side loading in every gear but 4th. Wayno is right a picture is in order.

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I think it's safer to disassemble the entire trans from the tailshaft forward instead of trying to pull the drive gear off the countershaft. It takes a really good puller and a bit of know-how to get that gear off without chipping the teeth. A press is the right tool for that job.

 

If disassembling a trans scares you, it's a matter of keeping track of parts. Pay careful attention when taking everything apart and work in a clean space so if you do drop something (like a detent ball or spring) you can find it easily. And make stacks as you go so you don't have to try and remember which way that gear went on or the thrust washer.

 

If you have access to a lathe, you can make a long tailshaft nut socket by cutting the right size socket in half and welding the hex portion to a piece of tubing and the drive portion to the other end. Now you don't need to use a wrench to get that tailshaft nut off and back on. But be careful using an impact gun on assembly, If the trans is worn (hub spacers, thrust washers) you can bind the trans and lock it up. Ask me how I know...

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Thanks all for your responses, I'll tell you what I was trying to do was to remove a badly beat-up input shaft bearing with a puller and thought I could do this without pulling the bell housing off and wasn't getting very far so I thought I'll just tap on the back side of the puller to try and free it up and that's when the input shaft more or less came off exposing the needle bearing and all. I guess I don't fear separating the trans as much as I once thought just not sure what other problems I've created. Cool website! just a ton of info here and seems like guys just willing to help. Thanks, Jeff   

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Usually the input shaft can only come off after the counter bearing has been pulled off the counter shaft below it. Picture maybe?

 

I can't see how you would get a grip on the mainshaft bearing to pull it. If you did, you may have damaged it, Like I said it shouldn't be able to come out.

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Usually the input shaft can only come off after the counter bearing has been pulled off the counter shaft below it. Picture maybe?

 

I can't see how you would get a grip on the mainshaft bearing to pull it. If you did, you may have damaged it, Like I said it shouldn't be able to come out.

Unless the synchro drive teeth were left behind...

 

That could be a huge problem.

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  • 3 months later...

Back at the '87 5-speed again, I guess I work very slowly, but anyway I think I've got things pretty much back on right and before I try and fit the  front case back on I've got a question on the sub-gear direction in front of the counter drive gear. I put the counter back on the same as it was, but is there a front side and a back side on the sub gear? Thanks to Mike or anyone else with advice, it's been fun learning new things. Jeff  

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