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Is an auto trans when doing a KA swap an option?


Drummerboy4as

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I’m slowly gathering parts and info for my eventual KA24DE swap. My plan is to get a salvage title ‘98-‘04 Frontier and strip it. 
My truck currently has a 3 speed auto and despite the inability to drive on the freeway I love it. Ideally I’d like to keep it an auto when I do the swap. What I’ve been unable to find info on is the dimensions on the Frontier auto trans. Will it physically fit in the tunnel of the 620? I know it’s a column shift so I’d have to figure out how to convert that but that can’t be too hard. 
 

Has anyone done it? My search results came up with nothing

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I do a lot of LS swaps in Toyota Land Cruisers and sometimes the customer opts to use an aftermarket shifter, but sometimes they want to keep the original Toyota shifter. The reason I bring this up is because you could probably use a generic floor shifter from someone like https://www.lokar.com/ . I bet that the shift detents are in a similar range but the geometry may require some math. When I use a Toyota shifter with a GM hydromatic trans, I simply lengthen the Toyota shift arm to the length required to match the throw of the arm on the trans.

 

Brian_D_5_Small_120_zpso8jqjec6.jpg

 

Brian_D_5_Small_126_zpsov1mq53r.jpg

 

Brian_D_5_Small_119_zpsnuf8qayu.jpg

 

Brian_D_5_Small_097_zps8jzpkekv.jpg

 

 

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5 minutes ago, Stoffregen Motorsports said:

I do a lot of LS swaps in Toyota Land Cruisers and sometimes the customer opts to use an aftermarket shifter, but sometimes they want to keep the original Toyota shifter. The reason I bring this up is because you could probably use a generic floor shifter from someone like https://www.lokar.com/ . I bet that the shift detents are in a similar range but the geometry may require some math. When I use a Toyota shifter with a GM hydromatic trans, I simply lengthen the Toyota shift arm to the length required to match the throw of the arm on the trans.

 

Brian_D_5_Small_120_zpso8jqjec6.jpg

 

Brian_D_5_Small_126_zpsov1mq53r.jpg

 

Brian_D_5_Small_119_zpsnuf8qayu.jpg

 

Brian_D_5_Small_097_zps8jzpkekv.jpg

 

 

Interesting! I’ll definitely look into that if using my stock shifter isn’t an option

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I don't know the length of the stock KA automatic it may be different from the 620 which is 31.5". As the KA can be fitted to a Z series 5 speed it should also fit the Z series automatic. If you can find the automatic/torque converter and flex plate from an '83 and up 720, mate it to the KA and it will fit perfectly into the 620 for length. 

 

The KA automatic has some emissions electronics for shifting so I don't know how this would effect the EFI or not if you keep that.. 

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Excellent info Mike! I had no idea about the emissions stuff. 
If I decide to go the car KA route I assume the the Z tranny will also bolt up to that?

 

I plan to keep the EFI stuff but I’d like to ditch as much emissions stuff as possible. 
 

How does the 620 speedo match up with the 720 trans? Probably a lot better than the KA trans 😆

Edited by Drummerboy4as
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On 1/21/2020 at 5:48 AM, datzenmike said:

I don't know the length of the stock KA automatic it may be different from the 620 which is 31.5". As the KA can be fitted to a Z series 5 speed it should also fit the Z series automatic. If you can find the automatic/torque converter and flex plate from an '83 and up 720, mate it to the KA and it will fit perfectly into the 620 for length. 

 

The KA automatic has some emissions electronics for shifting so I don't know how this would effect the EFI or not if you keep that.. 

Are you referring to the L4N71B? 

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The L4N71B (4 speed auto) began and ended with the Z24i in the 86-89 D21 Hardbody. When the KA24E was introduced a newer emissions controlled (or controlling) RL4R01A 4 speed automatic was introduced with it. The automatic 'talked' with the emissions and EFI controls to tailor the up and down shifts for best control of emissions and economy. This would be the best automatic even if you had to modify the driveshaft length.

 

The D21  L4N71B will bolt up to the KA and would be within an inch? (I think it was 30" long) of the 3N71B's 31.5" length. Here's my L4N71B (top) and an earlier 620 3N71B...

OJcTdVr.jpg

 

Or

 

Get a L3N71B from a Z24 720. It has the correct bolt pattern and is exactly the same length as the 620 automatic. Three speed and a locking TC.

 

Or

 

Get the bell from a 3N71B from a pre '82 Z series automatic and swap onto the 620 automatic. (I think the 620 automatic a bit lightweight for a KA)

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2 hours ago, datzenmike said:

When the KA24E was introduced a newer emissions controlled (or controlling) RL4R01A 4 speed automatic was introduced with it. The automatic 'talked' with the emissions and EFI controls to tailor the up and down shifts for best control of emissions and economy. This would be the best automatic even if you had to modify the driveshaft length.

If I had no emissions equipment would the trans just function off of hydraulics or does it need some sort of ecu input? I’m keeping the EFI but removing the EGR and whatnot. 

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Not sure if this helps, but I dropped a KA-E in my 521 and used a lockup 3N71 from a early 80’s S11. This was quite a while ago so I don’t remember the specifics but I do recall having to custom make a crank bushing for the torque converter to center on. Might have had to drill new holes in the flex plate for the converter also. While the trans bolted up fine, it was the converter interface that required a little fab.

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Found this gigantic doc on the RL4R01A and the RE4R01A. After a cursory comparison of the L and E and it appears that

the L just looks at the ECU for TPS and Coolant temp.

Whereas the E looks at Throttle position sensor,
Closed throttle position switch, Wide open throttle position switch, Engine speed signal,
A/T fluid temperature sensor, Revolution sensor, and Vehicle speed sensor. 
 

Document states that the E is electronically controlled and the L is hydraulic. So I think it’s safe to say that as long as I stay away from the E I should be golden.

 

The doc, tons of info on the two trans

http://pdf.textfiles.com/manuals/AUTOMOBILE/NISSAN/frontier/2001/at.pdf

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Another thing I have to consider is auto vs manual ecu. The engine I have is from a manual and I’m having trouble finding if an auto ecu will work with a manual engine. 
Logically it would I think? I would think Nissan would make one engine assembly/harness and just have an auto and a manual ecu. One would take/give input to an auto trans and one wouldn’t. 
Lots of information on auto>manual swaps not so many manual>auto. I can’t imagine why 🤦🏻‍♂️

Edit: AT vs MT TPS sensor PN AT part# is 22620-45V00 and the manual part# is 22620-53F00

 

Little info dump from Jatco if anyone’s curious 

 
Edited by Drummerboy4as
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Some AT ECU info courtesy of Jim Wolf
 

Man PN A11-B45 G08

early 91 240SX Fifty state S13-KA24DE

Nissan PN 23710-53F10

 

Man PN A11-B45 G71

91-94 240SX  Fifty state S13-KA24DE

Nissan PN 23710-53F11

 

Man PN A11-C03 G61

91-93 240SX (conv) Fifty state S13-KA24DE Nissan PN 23710-59F10

 

Man PN A11-C04 G24

94 240SX (conv) Fifty state S13-KA24DE

Nissan PN 23710-59F12

 

And if anyone wants to reference their ECU # for info on donor vehicle

http://jimwolftechnology.com/wolfpdf/ECU-ID.PDF

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Hey @datzenmike what do you know about flex plates? I’m trying to locate one for the240sx  RE4R01A and I’m coming up empty handed. Any idea if they’re interchangeable among other KA’s I would assume FWD vehicles are a no go but I honestly have no idea. My research hasn’t found an answer

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No idea.

 

But the flex plate was unique to the S13 and S14  KA24E and KA24DE engines. The D21 Hardbody KAs used a different part number for the flex plate but used the same RE4R01A. FWD numbers are also different and my info, such as it is, shows them separate from each other.  

 

It does not mean they are so different they will NOT work if (for example) you were to modify it with an extra bolt hole or something like that. There is something different about all these flex plates but I have no idea what that difference is. Maybe the TCs are different.

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TC = tooth count? I’ll have to keep digging and see if I can find the diameter. 
I believe the various Nissan KAs that use the RE4 (hardbody, 240sx, pathfinder maybe) use the same bell housing which would mean the starter location is the same and therefore the diameter (just guessing here). I’ll have to look up starter #s maybe that’ll get me a different tooth count. 
 

In other news I’ve discovered I need an A/T Control Unit to use the RE4 auto and a harness that goes from the tranny to the main harness that is eluding me. 
 

So, for the future readers that want to mate an auto tranny to your KA, don’t. Just go manual 🤦🏻‍♂️

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On 1/21/2020 at 5:48 AM, datzenmike said:

 

I don't know the length of the stock KA automatic it may be different from the 620 which is 31.5".

For your records the A/T I have is from a 1992 240sx and measures at 32”. I can put a straight edge on it later and measure as it’s slightly over 32” but not more than an 1/8” or so. 
 

And do you measure to the very end of the prop shaft?

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6 hours ago, Drummerboy4as said:

For your records the A/T I have is from a 1992 240sx and measures at 32”. I can put a straight edge on it later and measure as it’s slightly over 32” but not more than an 1/8” or so. 
 

And do you measure to the very end of the prop shaft?

 

It's impossible to measure less than what it is but always easy to measure it too long. Stand it up on end and put a level across the driveshaft end, or 2x4, just something sticking straight out from it. Clip the tape measure on the bell somewhere and measure up to the straight edge. Make sure the tape is vertical like the transmission and it should be 8" or 9" out from the spline. This gives the best length and not the always longer slope distance.

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Been slowly chugging away at my project. Got the L20 and trans out and am able to compare it to the KA with auto. 
Motor mount to tail shaft of KA auto is only 1/2” longer, so we’re good there. 
The transmission mount is 3ish inches further to the rear. So I’m looking at modifying the trans x member. 
@datzenmike would you happen to have the measurements of the mounting location for the KA 5spd? I’m wondering if the auto is the same. Redeye makes a trans xmember for the 5spd (I think), would be tits if it worked for the auto too. 

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The 71C mount for the KA should have a the same mount location as the 71B used in the 620.

 

If you measure from the front where the transmission joins to the engine block back to the center of the two bolt holes in the casting of the mount area on the tail shaft... it's 21". This is a 71B but the 71C should be the same

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