2003 auto to manual conversion

[Lock]

I'm the second owner of my pretty much stock 03 Pathfinder SE (auto, part-time 4wd) since 2015. Things happened in 2020. Decided to convert the Pathfinder to manual. Bought a manual trans from a 2002, took my time, and in summer 2023 finished rebuilding it. Not including that here as it's pretty routine - all new synchros, bearings, input shaft and some gears that had chipped teeth, then back together.

 

If you have a 2000, 01 or 02 part-time or rwd you can swap in a manual, get a manual ECU, (deal with NATS), and be done. 

(You can't manual swap a full-time 4wd, fulltime unit only works with an auto)

 

My problem with the 03 was Nissan discontinued manuals in the US in late 2002 for model year 2003, which also had new revisions with a more advanced ECU including electric throttle body and other changes.
So I could either go 'backwards' to a US 2002 manual ECU and install throttle cable, find a wrecked US manual truck and swap everything across - or get an 03 manual ECU and make it work. I didn't want to go backwards. I'm also in WA which doesn't do smog checks so no issues modifying or mixing and matching.

 

Luckily, Nissan still sold the 03-04 as manual in Canada. Looking at parts diagrams in Amayama it looked like the Canadian auto 03 model was near-identical to the US model, so the manual couldn't be that different, I figured. The worst outcome was it wouldn't work at all, or that I'd have to keep spending money until it worked or I gave up. I took the gamble.

 

I reviewed the earlier Pathfinder auto to manual guide linked on this forum, and also looked up a lot of 350Z conversion forums as it's the same engine and ECU. Also Nissan Skyline and 300ZX forums as different engine, but same transmission. 

 

I found the throttle body changed part numbers in 07/2002 from cable to electric, so that was the cutover date. Anything after that was right.

 

 

I searched individual junk yards in Canada until I found a place selling a clutch pedal and bracket, ECU, and flywheel.

The tell with the 'right' car was there were no throttle/cruise cables in the engine bay pics, cuz electric throttle.

The yards that had what I needed were in rural Alberta. Apparently Alberta has a lot of R50 Pathfinders in their yards. I mainly used car-part.com.

 

I sent the ECU away to get NATS disabled so I wouldn't need to deal with it.

 

Got everything in and worked end of summer 2024, and wanted to share here. Pics and posts to follow once I get an image service set up. 

 

Edited April 10 by Lock

[Lock]

I had never rebuilt a manual trans before. Followed the service manual, "Beer Garage" (since deleted), and youtube videos and took my time. I used a toaster oven to make dropping the press fit gears back on easier.

 

 

 

I bought a factory shifter. But I thought it was too tall so I cut about an inch off it and welded. I am not a professional welder at all. But it has held up fine.

 

 

I also found and bought a NOS Pathfinder clutch, and a 350Z flywheel.

I figured a 350Z is the same engine and clutch, and the clutch and flywheel fit together. Seemed so far so good. 

 

Edited April 10 by Lock

[Lock]

First things first - remove the transfer case

 

 

Lots of extensions needed to get to bellhousing bolts. I bought proper long ones after this.

 

 

Auto transmission detached

 

 

Flexplate

 

 

Flexplate removed

 

 

Source of my rear engine oil leak (after clean up) - rear pan seal job was badly done

 

 

Sealed it up good. Also I didn't take a photo, but you need to remove the steel inner collar. It's a total pita to get out. It centers the torque converter, but the manual transmission uses a small brass one. There's videos online, the 350Z auto to manual conversion videos cover it. I couldn't get it out for hours and broke various tools, I thought that was the end of the project. But I got it out eventually with the exact right sized puller. 

 

 

Fortunately the R50 chassis has the clutch master cylinder hole already there under a plate

 

 

Turns out the auto trans computer sits on the other side of the clutch blank plate so both come out at once

 

 

Factory clutch master cylinder. I thought about steel clutch lines, but ended up using an ebay 240SX clutch line kit. Works fine.

 

 

 

Edited April 10 by Lock

[Lock]

Clutch pedal installed. I couldn't find a Pathy brake pedal - probably because its bracket wraps around the steering column. I kept hitting the brake when I went for the clutch, so I ended up just cutting the brake pedal the same size as the clutch pedal and it looks factory now

 

 

You can't really see, but the clutch pedal bracket goes where the auto trans computer used to be. It has a clutch starter switch but I didn't connect it (did connect the neutral start switch though)

 

 

The Pathfinder manual uses a pull clutch (not a regular push clutch) which I had to figure out how it works

 

 

Got the OEM parts

 

 

Assembled. It 'clicks' into the pressure plate on installation. Then to release you pull out that pin, and the fork falls out. You lift the collar on the clutch release bearing to release it from the pressure plate. It's kinda hard to explain without seeing it in action.

 

Edited April 10 by Lock

[Lock]

So first I tried a 350Z flywheel - but it was too high and wouldn't allow the pull clutch to work so couldn't release the clutch. So pulled the transmission out again, and next I installed a US '02 flywheel

But the signal plate is way different, it's for the cable throttle ECU and the engine wouldn't start

 

00-01-02 signal plate on left with like 300 or something holes. 03-04 signal plate on the right. The right side has 3x 10 holes. That's what I needed, but flywheel not flex plate

 

 

I found I needed part number 123105W90A (03-04 only) which is unique to the R50 Pathy due to the pull clutch. It was hard to find but found one in the UAE from I think partsouq

 

Correct flywheel installed

 

 

I found the starter motor had to be shimmed back about a 1/2 inch otherwise starter gear would hit the flywheel. There's an official part number for this, a plate the starter sits sandwiched under, but it's out of stock so I just used washers

 

 

OEM clutch plate is an Exedy

 

 

Pressure plate installed

 

 

It's pretty big as pressure plates go, but the pull clutch means the clutch pedal is light (is why they chose it for the Pathfinder - more grab but lighter to use)

 

 

 

Edited April 10 by Lock

[Lock]

A pic of the back of the new flywheel showing 03-04 signal plate

 

 

A view of the clutch fork from the outside. It pushes towards the engine, which pulls the pressure plate 'off' the clutch and flywheel

 

 

Edited April 10 by Lock

[Lock]

I made an adapter for my transmission jack to securely hold the manual transmission in place. I've used ordinary jacks to reinstall car transmissions before but this thing is pretty heavy even without the transfer case and I didn't want it falling on me

 

 

About to go in

 

 

Lining up manual transmissions just right to install is always annoying. Sometimes you gotta take it completely back out and down and start again. Sometimes it pops right in

 

 

You can see the innards of the transmission before the transfer case is attached. Without sealant the transmission oil would all seep out

 

 

Technically the manual transmission transfer case is different - it has a small gutter under the input shaft, and subgears to absorb shock. But nothing that is needed for the conversion. The auto transmission transfer case works fine. But you have to apply sealant as the back of the manual transmission is open

 

 

[Lock]

The manual transmission chassis cover plate was unavailable, so I cut the existing one to fit the manual shifter

The service manual says to fill the transmission from the shifter hole, so I did

 

 

Intermediate covers and soundproofing

 

 

Manual transmission trim installed

 

 

The original auto transmission connector block. I connected up the neutral position switch to the PNP relay so it only starts when the shifter is in neutral. And connected up the reverse lights, just four wires

 

 

 

Edited April 10 by Lock

[alexg89]

This is super cool. glad to see people out here still swapping in manuals lol

[CALPATHY]

That took some effort, I am glad I have the factory manual.  Great job!

 

[Lock]

Thanks! The end result was definitely worth it. 

A couple thoughts/comments, as this wasn't really a 'how-to' thread, mostly just sharing photos. 

I had to lock the power valves open because the manual doesn't control them. When closed, the engine pinged/knocked around 2-3krpm. Eventually I plan to take the manifold off and remove the power valves entirely (I did the threadlocker fix years ago).

The auto ECU might have worked with a CEL throwing transmission codes, but I didn't try. It gets some sensor data from the transmission so it probably wouldn't work.

Getting the flywheel was the toughest part. The only difference between the 01-02 and 03-04 flywheel is the sensor plate, which can be removed. So if one goes NLA you could buy the other and swap the plate.

You could probably use a 350Z flywheel and regular push clutch if you can weld aluminum (or make some kind of bracket) and swap the clutch slave cylinder to the other side. I read that the 90s Skylines can be converted from pull to push.

I've been driving it since the conversion, and hasn't missed a beat. It's nice to have a brand new manual transmission with new synchros that shift like butter. And you can leave it in 5th gear over 40mph even uphill.