1977 620 4spd to 5spd

[Newkid]

ok when i bought my truck, he gave me a five speed transmission from a later year datsun truck along with the drive line, is there a way to look on the transmission to see if i have the right transmission to swap in? because from what i understand and read, i can take a 80 datsun 720 5spd tranny and swap it for my 4spd along with changing the speedo drive so it would read correctly.. am i wrong?

[]2eDeYe]

As long as that 80 720 had the L20B (which it should) it should be a direct swap.

 

If you post a pic of the 5-speed we can id it for ya :)

[flatcat19]

More to it that that.

 

I'd say a starting point is a picture...then wait for DMike to show his face.

 

If he doesn't show right away, just start typing this...

 

DOUCHEBAG!!! JERSEY SHORE!!! FREE ASIAN TRANNIES!!!

 

^

He'll be with you shortly.

 

 

:lol:

[datzenmike]

Who disturbs my wa????

 

 

 

An '80 5 speed will swap into the '77 with no other changes.................................. providing it is indeed from a '80 720. A picture of it, multiple pictures would be better, will help ID it better and tell if it is an L series 5 speed.

 

Keep in mind that a 4x4 5speed will not have a speedometer drive so it has to be a 2wd if you want your speedometer working. Your '77 speedo drive pinion will not fit the '80 2wd transmission to keep you speedometer accurate... but there is an easy trick to fix that.

[Newkid]

L8 is stamped on it

 

so whats the verdict you guys?

[Newkid]

no one?

[datzenmike]

It's an FS5W71B 5 speed for an L series motor. It may have come out of an '80 truck but that is not an '80 transmission. Could be a '77-'79 truck or 280z or first year zx 5 speed. This is good because you can swap your 4 speed speedo pinion into it to keep your speedometer accurate.

 

It will fit and work in your '77 no problem.

 

Be sure to use your 4 speed release bearing collar as it's unknown what this one is for...

 

 

... and we know yours works with your clutch. Use a new bearing of course.

 

Before I forget, pry the old tail stock seal out and replace. It's old and used and will be having a different drive shaft shoved in it. Do it now while it's easy to get at and it will save doing later when in the truck. The part number is #32136-U0100, about $8 at dealer and $5 at NAPA.

 

 

 

Start by tapping with a hammer, then place a block of wood over it and hammer it flush, finish tapping in all the way with wooden dowel. The new seal may be thinner than the one you removed.... this is so the new seal will contact a new unworn surface on the drive shaft spline and seal better.

 

 

Refill after installing with 80w90 GL4 oil or anything 'yellow metal safe' to protect the synchros. 2 liters or 2 US quarts will fill it.Use 3 feet of garden hose from beside the engine and running into the fill hole on driver's side. Buy a kitchen funnel from the dollar store. If cold, warm the oil indoors to speed up the fill.

[Newkid]

thanx datzenmike

[]2eDeYe]

+1 for Tech. :D

[DaveyDaveDaveDave]

So whats the trick to keeping the speedo accurate? Im doing the same swap (5 spd from a 80 720) to my 77. Aaaaand, while were at it, hows that do with the rear gears of a 77? I promise, I looked. Checked old datsuns, searched ratsun via google...

[datzenmike]

First of all the speedometer drive gear in the transmission is intimately mated to the differential ratio. They work together and should not be separated.

 

If you are swapping in a new transmission the old speedo pinion should go into the new one to keep it with the old differential.

 

But not so fast, there is a small problem with this. Changes were made to the 71B transmission and pre '80 speedo pinions will not fit '80 and newer transmissions... BUT they can be easily modified and made to fit.

 

All pinions have a small key way slot in their sides that a locking tab fits into, and this tab is held in place with a small 10 mm bolt. Pre '80s pinions have the slot exactly 180 degrees around on the other side compared to the '80 and up pinions. So, all you have to do is cut a new slot for the tab. I used a small angle grinder and a $4 metal cutting disc. All I did was cut a slot that the lock tab will fit but on the oposite side.

 

This isn't the one I made because it worked the first try and I wasn't about to drain the tranny and take it out for a picture. This shows the keyway.

 

 

This one has a second key way cut in it and allows an older pinion to work in the newer transmission.

 

 

 

.

[DaveyDaveDaveDave]

Oh heck yes. Did this before (love scoring 5 spds from 1980 720s) but hated the speedo being off. Cant believe how simple a fix if Id been paying attention!

[datzenmike]

Well you could count the teeth on your L speedo pinion and search for the same cog from a newer transmission. This will work also, but cutting a new slot works.