My 73 Suby drivetrain conversion upgrade!, New rebuild going in January 2025 Options

[JRust]

Great news! That 3.90 trans will probably be fine for you. FYI if can't resolve the trouble with the speedo you can send it back to Speedhut and have it converted to GPS...I had the same issue so that's what I did.

Enjoy it!

Yeah I am sure it is a GPS unit. I don't know it has been sitting with no power for so long. I 'll look into it more this week. I took it out today for a couple hours of driving. No great roads as it was a service call for work. So most was on the freeways. Still it ran great I had no real issues. My throttle hangs up just a bit. I'm pretty sure that is just tied to my accelerator cable. I still need to order a custom one this week. I also need to build up a better base for my shifter. Sitting a bit to low for me. Plus I moved my ECU into the cab. I don't have much extra wiring so it is kinda stuck dead center where the backpad would be. I just carpeted my firewall so no big deal. Just my old armrest setup won't work

As far as gearing on the tranny. It is definitely different as my NA 2.5 had a forester tranny with the 4.44 gears. Which was really perfect gearing as the power really suited the setup. Was great at the autoX. This gearing is different & the power really in a different spot. Turbo really starts spooling around 4k rpm. Not as much low end grunt as my previous setup. I would be a bit quicker off the line with my NA setup. Although I would catch up quick with my turbo. LOL! I hit my rev limiter about 55 in second gear & 75 in 3rd.

[Andyrew]

As far as gearing on the tranny. It is definitely different as my NA 2.5 had a forester tranny with the 4.44 gears. Which was really perfect gearing as the power really suited the setup. Was great at the autoX. This gearing is different & the power really in a different spot. Turbo really starts spooling around 4k rpm. Not as much low end grunt as my previous setup. I would be a bit quicker off the line with my NA setup. Although I would catch up quick with my turbo. LOL! I hit my rev limiter about 55 in second gear & 75 in 3rd.

That third is too short IMHO. 20mph in a gear? Way to short.

What gearbox do you have available and what ratios do you have??

You have 3k worth of powerband so you'll want to have some headroom above and below it for shifting.

Link below is what I use for calculating my gears.
https://www.dropbox.com/s/8kikaf08oij9ijx/A...atios.xlsx?dl=0

I would suggest a taller final drive if you can find it. Something that puts first about 35-40, second about 60-70, and third about 100-110.

[JRust]

That third is too short IMHO. 20mph in a gear? Way to short.

What gearbox do you have available and what ratios do you have??

You have 3k worth of powerband so you'll want to have some headroom above and below it for shifting.

Link below is what I use for calculating my gears.
https://www.dropbox.com/s/8kikaf08oij9ijx/A...atios.xlsx?dl=0

I would suggest a taller final drive if you can find it. Something that puts first about 35-40, second about 60-70, and third about 100-110.

I am guestimating on the 3rd gear. It probably is higher than 75. Trying to look at my phone on the seat next to me isn't the easiest thing. I need to get my speedometer working. LOL. I didn't actually hit my rev limiter in 3rd. Even second may be a bit higher. I'll have to get a passenger out with me to get some legit ones

[Amenson]

I was digging through some old files looking for data and failed but I did find some ratio calculations I did when I was picking out my trans.

I ended up with a 09 WRX which has different 1st-3rd than the earler stuff.

3.9 3.166 1.882 1.296 0.972 0.738 - '08-up USDM WRX

3.9 Final drive


4.11 Final drive


This is likely what you have.

3.9 3.454 1.947 1.366 0.972 0.738 - '02-'05 USDM WRX 

[Andyrew]

That 3.9 final drive doesn't look to bad.

[Chris H.]

If you have a GPS speedo just call Speedhut and they should fix it for you. You send it in, they fix it, send it back to you. I had to send mine back for that as well. It barely registered.

But first...make sure the antenna is plugged in and it has a very clear line of sight. If it's behind a visor or something it may not register. I moved my antenna recently for a cleaner look and had to move it back on top of the dash so it would register reliably.

[914forme]

I have ridden with Scott and 1st is useless. It did motivate the rear end to make a weird spinning tire noise I never heard in a 914 with a 4 cylinder. But then he could induce that same noise at speed, going around corners and the like.

I wholeheartedly approve BTW, I like things that can spin tires, and leave 11s all day long. (IMG:style_emoticons/default/aktion035.gif)

[Chris914n6]

I went with the tallest ratio I could get, not that it was really that much difference.

With my Nissan6 190hp/205tq I use 2-3 around town and H 5th is great on highway @90mph

The 3.5L 'upgrade' will be 300ish, like yours with more boost. The 914 box would work fine with the clutch I already have but I don't want breaking a trans to be always on my, mind so a 2011 WRX box swap is in the works. I'd actually bump 5th higher if it was cheaper, I've got plenty of TQ at 3k to do it.

At 1000lbs lighter I think you will be zipping thru gears more often to no real benefit vs the Subaru.

[JRust]

Put on a front spoiler I picked up a while ago. Thanks Don! This thing sits pretty dang low. I scraped going out my driveway & a few other spots as well. I do like the look of it though.

For gearing I was off Andrew. So 2nd I can probably hit 70 before my rev limiter. 3rd I am pushing 100. Still a bit slow telling as my phone GPS was lagging a bit. This will just take some getting used too. I am pretty lightweight in that I have never really run my motor up this high. I always shifted earlier as my old setup power band was really on the lower end. So I am really struggling running it up over 6k. My rev limiter is set at 7. Hoping to have a few decent days without rain so I can put some more miles on it

[Robarabian]

I'm smiling for you right now. Car looks amazing. Great job!

Put on a front spoiler I picked up a while ago. Thanks Don! This thing sits pretty dang low. I scraped going out my driveway & a few other spots as well. I do like the look of it though.

For gearing I was off Andrew. So 2nd I can probably hit 70 before my rev limiter. 3rd I am pushing 100. Still a bit slow telling as my phone GPS was lagging a bit. This will just take some getting used too. I am pretty lightweight in that I have never really run my motor up this high. I always shifted earlier as my old setup power band was really on the lower end. So I am really struggling running it up over 6k. My rev limiter is set at 7. Hoping to have a few decent days without rain so I can put some more miles on it

[mepstein]

Love the car. The spoiler not so much - sorry. I'm glad you are back on the road and can start enjoying the car again.

[sixnotfour]

Kevin, Loves that front spoiler...half a block and he managed to to tear it of ..REDRUM, doing a U-turn.... (IMG:style_emoticons/default/hissyfit.gif) (IMG:style_emoticons/default/beerchug.gif) @rhodyguy

[JRust]

Love the car. The spoiler not so much - sorry. I'm glad you are back on the road and can start enjoying the car again.

I'm a little split on it. I like the overall look & that if fits with the flares on each end. I don't like how low to the ground it goes. Time will tell if i will keep it or not

[Andyrew]

For gearing I was off Andrew. So 2nd I can probably hit 70 before my rev limiter. 3rd I am pushing 100.

That's pretty good then, 2nd will be the autox gear and 3rd and second the canyon gear (you have enough power now you can baby the engine a bit and be up a gear on your powerband).



How bout some in car video? Let's hear that turbo!

[JRust]

That's pretty good then, 2nd will be the autox gear and 3rd and second the canyon gear (you have enough power now you can baby the engine a bit and be up a gear on your powerband).

How bout some in car video? Let's hear that turbo!

Yeah I'll get some video soon. Would like to have my speedo working. I will wait on video until I get my final tune later this week. I can't wait to get that done. Just realizing how much I need to do getting my interior back together. I missing half the stuff I pulled out (IMG:style_emoticons/default/confused24.gif) . I swear it is in my garage somewhere

[MichiganMat]

Have you adjusted your linkage since this photo was taken?

I ask because this photo shows exactly the kind of mounting that I did with the ZeroDB linkage that was incorrect.

The little arm that mounts to the transmission output shaft should not be attached at the little hole that exists in the linkage. It needs to be mounted as close to the taper as possible, with the goal (and heres the important part) of the linkage being as squared up (i.e. 90-degree angles everywhere) as possible when the transmission is in neutral.

If the arm is mounted at the stock hole in the transmission output shaft, the angles are not 90, and the shift pattern at the shifter will feel not like an |-|-|, but much more like: |-\-/ because of the bad geometry.

On my racecar, the bad geo at the shifter resulted in 2 (!!!) mis-shifts at the track. I ultimately found the bad geometry, drilled a new hole in the output shaft, and sternly suggested to ZeroDB to send instructions with their kit.

Very best,
Mat

Looking good Jamie!
I went to the zero decibel stuff. Much tighter than before! Love it.

[PanelBilly]

Video!

[JRust]

It's sunny & I've got a run I need to make to the coast. I'll try to get some video. I was out last night & went under a bridge. Happened to be accelerating & holy shit my car is loud. I did have the top off for the first time since the new motor. I definitely did not accomplish the sleeper setup with my car (IMG:style_emoticons/default/evilgrin.gif)

[pploco]

(IMG:style_emoticons/default/clap.gif)

The car looks great! I love the front spoiler.

[JRust]

Went back through my paperwork. Looks like my Speedometer is not a GPS unit. It was run off the VSS going by what Dean wrote. Is that on the transmission. I'm going to need to figure out how to wire that back up. I may have sent that off with my old setup. Would that just be a wire coming from the sensor to my speedometer? Is it as simple as that?