Transmission options

[justin 620]

Hey there, I have a 79 620 with a shot transmition, and a 92 nissan hard-boby with a fine tranny, drive shaft, and rear end, my question is whether or not the transmition from the 92 would fit in my 620? I have plans to later on swap out the rear end as well, but that involves some cutting and welding.

[Braden]

ha ha no not just a bolt in. bellhousing swap maybe? but then the tranny would be cock-eyed?

[nismo dr]

first, transmission. second you don't say which engine is in either vehicle, L20 in the 620 I presume, vg or ka in the hardbody? third, either way I don't think it will work. The napz trans can have the bellhousing swapped for a l motor but I don't think you can do it with the later - why not swap whole powertrain?

[datzenmike]

This is actually a triple post!!!! WTF??

 

 

 

The D-21 should be a 2wd. 4 cylinder motor to make this the easiest. A VG motor tranny won't bolt to the L series motor in the '79..... but the L series tranny can be split and the front case bolted to the VG tranny. This opens a can of worms. Pretty sure the VG tranny will have a different drive shaft spline so have that welded to you shortened '79 drive shaft. (see * below)

 

 

The FS5W71C from the Z24i or KA24E 4 cyl. 2wd D-21 will physically bolt to the '79 motor but because of differences in engine placement tilt it will lean heavily to the right with the shifter over in the pass seat. I suppose the shifter could be bent to the left to compensate for this. The tranny tunnel hole may need to be enlarged. The rear tranny mount will also be wrong and need a wedge to be properly supported. Do not try to run without this as the rubber will fail or cause the rubber engine mount to fail. Never seen this done but no reason it can't and keeps the C tranny intact.

 

* The FS5W71C is also longer than the FS5W71B in the '79 so the front half of the 2 piece drive shaft will need shortening.

 

IF you have a 4 cyl. D21 there is no use swapping differentials as it is the same as in your '79 just newer. The whole rear end assy. is also a couple of inches wider on each side.

[justin 620]

Well it is the l20b with a 5 speed, and it's a KA24 in the hardbody, the problem with swapping the whole power train is that the motor is seized. If the money to fix that motor was available it already would have been out, fixed, and put in my 620, but it just isn't there. Thanks Mike, for pointing out that yes, I have asked this question before, but since nobody actually decided to give me a straight answer I asked it directly. I wanted to know this because going out and dropping money for a transmition for my truck wouldn't make any sense if i had one sitting next to my house.

Would the tranny out of an '82 Datsun pick-up work? or did they switch it out after '80?

[datzenmike]

Has to be a 2wd and the tranny must be 31 1/2" long. The '82 would be a Z series motor and has the same tilt problem as the KA motor. The good news is it is the same length (no d/s shortening) and the L series front case will fit on without any changes. A simple front case swap makes it an L series 5 spd. All you need is a 12mm socket, extension and ratchet, snap ring pliers or a couple of screw drivers and some gasket sealer (not RTV) sealer to put it together with.

 

Here is something I did in the How To section. How to remove the front case from an FS5W71B

 

(the L series case will fit the KA tranny, but the counter bearing has to be swapped and the 1st/2nd shift rod hole in the L case drilled out for the larger KA shift rod. I didn't mention this in the other post because there was enough differences and shortening the drive shaft.)

[justin 620]

Ok, so a transmition from an '82 will work if I switch the front case from mine over to it?

[datzenmike]

Yes as long as it is 2wd and 31 1/2" long. 4X4 trannys don't have a speedo drive in them so what good is that? There are 26" 5 speeds in the 720 trucks, you don't want that.

 

You will need the '82 shifter, possibly. Actually very likely.

[justin 620]

Alright well thank you all for the help, I'll have to get the specs on the '82, but it should work.

[crowebar]

Yes as long as it is 2wd and 31 1/2" long. 4X4 trannys don't have a speedo drive in them so what good is that? There are 26" 5 speeds in the 720 trucks, you don't want that.

 

You will need the '82 shifter, possibly. Actually very likely.

datzenmike: The '83 datsun kingcab 4x4 has a FS5W71B transmission with the short tail (12"). Are there other transmissions that will work within the confines??

 

Regards, crowebar

[wayno]

This is actually a triple post!!!! WTF??

 

 

 

The D-21 should be a 2wd. 4 cylinder motor to make this the easiest. A VG motor tranny won't bolt to the L series motor in the '79..... but the L series tranny can be split and the front case bolted to the VG tranny. This opens a can of worms. Pretty sure the VG tranny will have a different drive shaft spline so have that welded to you shortened '79 drive shaft. (see * below)

 

 

The FS5W71C from the Z24i or KA24E 4 cyl. 2wd D-21 will physically bolt to the '79 motor but because of differences in engine placement tilt it will lean heavily to the right with the shifter over in the pass seat. I suppose the shifter could be bent to the left to compensate for this. The tranny tunnel hole may need to be enlarged. The rear tranny mount will also be wrong and need a wedge to be properly supported. Do not try to run without this as the rubber will fail or cause the rubber engine mount to fail. Never seen this done but no reason it can't and keeps the C tranny intact.

 

* The FS5W71C is also longer than the FS5W71B in the '79 so the front half of the 2 piece drive shaft will need shortening.

 

IF you have a 4 cyl. D21 there is no use swapping differentials as it is the same as in your '79 just newer. The whole rear end assy. is also a couple of inches wider on each side.

 

Hey Datzenmike, are you saying here that I could use the VG30 front transmission case and the gearing(back half) of the 1985 shortshaft 5 spd. to make a shortshaft that will bolt to a VG30. I really need to know if this is an option for a 521 VG30 conversion. wayno

[datzenmike]

If you have an FS5W71C from a VG30 motor, car or truck, the front case half should fit the older FS5W71B (long or short tail. I don't see why not.

 

The VG tranny will have a large 62mm front counter bearing in it so the transmission that you put into it may have the smaller 56mm one on it. This is an easy fix, just use a gear puller and remove the 56mm and tap a 62mm back on. (I would get a new one) Around '85 the FS5W71Bs got this upgrade so you may be lucky and not need to do this.

 

The VG tranny will have a larger diameter 1st/2nd shift rod. The very front of the shift rods are supported by the front case so the VG case will have a larger 1st/2nd hole in it. Since the FS5W71B will likely have the older smaller 14mm shift rod, while the hole in the case will be 16mm. I don't know if 2mm (0.078") will make any difference. The shift rod simply has to slide forward and back in it.

 

 

FS5W71B front case. Note that all three shift rod holes are the same size (14mm) The counter bearing hole (bottom) is 56mm

 

 

FS5W71C front case. Note that the top shift rod hole is slightly larger than the other two below it . Also the counter bearing hole is slightly larger (62mm) and there is less space between it and the main bearing above it.

* note the' J' shape and small hole in the 2 o'clock position on the upper main bearing hole. This allows splash oil to enter the front cover plate and pass down to the counter bearing to better lubricate it. There is also an extra hole just to the left between the upper main and lower counter bearing holes for an exit. Refer to the cover plate picture further below below.

 

 

Use the VG front cover plate to fit over the larger counter bearing.

 

FS5W71B, left, and FS5W71C, right cover plates. Note the 'C' has slightly larger counter bearing cavity and best of all passages for superior oiling of the counter bearing.

 

I guess you are wanting a 26" 5 speed for your 521 that will allow a VG motor to be bolted to it?

[wayno]

If you have an FS5W71C from a VG30 motor, car or truck, the front case half should fit the older FS5W71B (long or short tail. I don't see why not.

 

The VG tranny will have a large 62mm front counter bearing in it so the transmission that you put into it may have the smaller 56mm one on it. This is an easy fix, just use a gear puller and remove the 56mm and tap a 62mm back on. (I would get a new one) Around '85 the FS5W71Bs got this upgrade so you may be lucky and not need to do this.

 

The VG tranny will have a larger diameter 1st/2nd shift rod. The very front of the shift rods are supported by the front case so the VG case will have a larger 1st/2nd hole in it. Since the FS5W71B will likely have the older smaller 14mm shift rod, the hole in the case will be 16mm. I don't know if 2mm (0.078") will make any difference. The shift rod simply has to slide forward and back in it.

 

I guess you are wanting a 26" 5 speed for your 521 that will allow a VG motor to be bolted to it?

That is one of the plans, I have lots of plans, but I do have a VG30 from a 200SX with an automatic, really don't want an automatic. I measured out the 66 520, and there just wasn't enough room, so it will be a 521. But I have another 320 project before the VG project.

[wayno]

Is the upper shifter rod hole size going to become an issue? I would put a sleeve in the hole but am afraid that it could slide with the shaft and lock the transmission in that gear if it came all the way out of the hole, I will have to look at this shaft somemore and make a desision. Will that J shaped extra piece of metal interfere with anything on the late 720 shortshaft gears? When I first read your reply there were no photos, :lol: then after I replied and posted, your reply was changed, totally differant, you did an edit, correct? There were two differant sized lower countershaft bearings in the 720 series transmissions, they put a bigger countershaft bearing in sometime around 84-85, is this another even bigger countershaft bearing, or is it the same size as the 85-86 shortshaft bearing? For some reason it even looks like a bigger bearing hole in the front cover photos :lol: than the 85-86 cover, maybe it is the extra channels that have been cut into the front cover for extra lubracation that makes it look bigger, and I do realize the the first case photo was of an early 720 longshaft 5 speed case. All this talk about the transmission wants me to start on this project while it's fresh in my mind, but I have other ones I am working on at the moment. Here is a tease.

 

[datzenmike]

Is the upper shifter rod hole size going to become an issue? I would put a sleeve in the hole but am afraid that it could slide with the shaft and lock the transmission in that gear if it came all the way out of the hole, I will have to look at this shaft somemore and make a desision. Will that J shaped extra piece of metal interfere with anything on the late 720 shortshaft gears?

 

I don't think it will matter but if you shim it you don't want it falling out later. As for clearance around the J... The top main drive gear is smaller than the bearing in front of it so is smaller than the hole.

 

 

When I first read your reply there were no photos, :lol: then after I replied and posted, your reply was changed, totally differant, you did an edit, correct? There were two differant sized lower countershaft bearings in the 720 series transmissions, they put a bigger countershaft bearing in sometime around 84-85, is this another even bigger countershaft bearing, or is it the same size as the 85-86 shortshaft bearing? For some reason it even looks like a bigger bearing hole in the front cover photos :lol: than the 85-86 cover, maybe it is the extra channels that have been cut into the front cover for extra lubracation that makes it look bigger, and I do realize the the first case photo was of an early 720 longshaft 5 speed case. All this talk about the transmission wants me to start on this project while it's fresh in my mind, but I have other ones I am working on at the moment. Here is a tease.

 

I finished the text and posted, only to change my mind and add pictures, which explain better anyway. As to the counter shaft front bearing there were only two sizes. 56mm from '73 through '84 and changing to 62mm after. I have an '85 CA18ET and an unknown SD diesel and both have the 62mm bearing. The first picture is actually a 4 speed but identical to the 5 speed and is pre '80 I think. It isn't a short shaft and everything that makes it a short is primarily in the back anyway.

[Bullet_theory]

ive found out, even with info from a professional trans rebuilder.... mike will prove you wrong .... fact