Need info on swapping tranny speedo gears from 720/620

[ahoogakev]

Hello , I was just down at my local Pick and Pull scrap yard and saw a 1984 4 by 4 (720) that had a 5 speed tranny in it, I believe I have read on this forum in the past, that the problem with swapping this tranny into the 620, is that it has no speedo drive gear, and thus you won't have a speedo if you use it, is that correct? You may recall I asked a few months ago about doing a 720 into 620 tranny swap, I was told the front cover would need swapping and possibly the front bearing - well that was great advice and that is exactly what I did- only to discover the 5 speed I swapped in, howls and growls a bit!!! So this is why I am still looking for another one.

If it is just a matter of pressing the speedo drive gear from one tranny to the other, I could probably do that - but if the tranny main shaft is machined down or the speedo gear is actually part of the main shaft, then I would be beat - does anyone know? It seems a shame to have to pass on a 5 speed just becuase it has no speedo drive gear!

By the way , I also swapped in a high speed rear end (3.888) after following the excellent advice given on Ratsun, that worked out great ( never done one before either!) Thus this truck now has 5 speed, 3.8 and one inch oversized tires, I briefly drove it in 5 and the revs were way down ( didn't drive much in 5 as the tranny really shakes in OD).Gears 1 through 4 are much better and I can probably live with this tranny for a while until I find a better one or put a re-build kit in it,I just won't drive in OD.

If it matters the bad tranny I have in it now, was from an 1985 2 wheel drive, I can't find decent pics of how the main shaft is made in my Haines book,Thanks,Kev

[datzenmike]

The 4x4 casting isn't machined for the speedo but you could swap another rear case half from a 2wd that does! You will need to swap the plastic worm gear onto the main shaft to drive it. Just a pair of snap rings and it slides off.

 

I'll post a picture of it. The rear comes off way way easier than the front.

[ahoogakev]

Thanks a lot for the info Mike, would I have to machine a groove for the snap ring to go into on the 4 by 4 shaft, or do they all have that? Thanks,Kev

[ahoogakev]

Heres my first attempt at posting a picture, lets see if this works, if not the picture can be seen at :

 

http://s946.photobucket.com/albums/ad306/ahoogakev/Kev76Datsun/?action=view&current=BlueOriginal4SpeedTranny.jpg

 

This is my old 4 speed tranny that I took out,I haven't looked closely at it, but I think that it has the speedo drive machined right into the shaft? Kev

http://s946.photobucket.com/albums/ad306/ahoogakev/Kev76Datsun/?action=view&current=BlueOriginal4SpeedTranny