Automatic Transmission Swap? New 1991 NSX Owner (Bay Area CA)

Joined
5 December 2023
Messages
12
Hello all,

I am a longtime lurker on these threads and a first-time poster as a new 1991 NSX owner. I’ve wanted an NSX as my dream car ever since high school and have recently been able to finally get my hands on one for a good price, albeit an automatic rather than a manual. I was able to find an auto NSX that was virtually all stock and still runs relatively great despite its age and about 100k mileage (there was a mileage/odometer discrepancy, which also contributed to the low price). Nevertheless, it is a great car and driving it has been incredibly fun, even with the auto transmission. After driving it though, I have come to the realization that I would ultimately like to have a manual NSX and I now have a dilemma that I would like to ask for advice from those with experience in this forum.

Should I keep my existing auto NSX and eventually swap the transmission to a manual when the auto transmission starts to fail/need maintenance? Or should I sell my auto NSX and try to buy a manual NSX down the road in a few years? Let me preface this with the fact that I was able to get my auto NSX for a great price; at least $15-20k+ lower than a comparable manual (though at the prices I have been seeing lately, probably closer to $25-30k+ less). I also plan to keep and enjoy driving this car as an automatic for the next couple of years or so as it runs relatively great and is a lot of fun, so this would be a future project that I could save up for/work on a little at a time. Since I am planning on keeping it for a while, I will perform any maintenance/upgrades that it may need, so this would also seem to be more of a sunk cost to me and incentivize me to swap the transmission since I will be already investing time/money into the car (TB/WP service was already done, but the car needs new wheels/tires, ABS/power-steering light is on, would change out stereo/lights eventually, maybe change the paint color, etc.) I probably would not touch the power-steering though, as it isn’t that much of an issue for me.

From those of you who have swapped your automatic to a manual, how was the process (length, difficulty, total price, etc.) and how well has it held up after the swap? Does it drive the same as a stock manual? How would the value of the car hold up, if I needed to sell the car in the future(this is my dream car so I have no plans to ever sell, but would still like to make sure that I am not bringing down the value too much)? Would the fact that it was swapped to a manual still allow it to retain the market value of a manual NSX, or would that bring it down significantly?

I am located in the Bay Area (East Bay) and would also like to know some reputable NSX shops close by to get maintenance/work done (preferably near Fremont/San Jose if possible). Also, would any of these shops be able to properly take on the task of performing a transmission swap?

Thank you all in advance!
 
I am located in the Bay Area (East Bay) and would also like to know some reputable NSX shops close by to get maintenance/work done (preferably near Fremont/San Jose if possible).
Hill Top Auto is in Daly City, but I live in the South Bay and I've been driving past dozens of other Honda/Acura shops to get my car serviced there since 2005. Don knows what he's doing.

Hill Top Auto Services, Inc
20 Theta Avenue
Daly City, CA 94014
650 991-8838
 
Firstly, congratulations on your dream car. Enjoy adding those miles.

Another option for your maintenance is https://www.scautosolutions.com/
I take my car there. Talk to Kenneth or Andrew.

In regards to the transmission swap, I think the hard part is finding the transmission. I've heard they are getting harder to locate. Ping the shop mentioned above, I think they had one in stock, but I don't recall it's condition or whether they still have it.

You asked about holding its value after the swap. That's a tricky question. I think it might scare off some potential buyers and thus lower its price since it didn't come from the factory with the transmission. Some folks like "numbers matching" samples.

My suggestion is to enjoy the car with the auto, especially with the terrible Bay Area traffic. In the meantime, keep your eyes opened for transmissions. If you find one, buy it before someone else does and then make your decision. You can always resell the transmission.
 
Last edited:
I have a little bit of experience with the swap. :) Short version: just get a manual NSX.

Long Version:
There are two ways you can go. A "full" swap involves:
  • Clutch master and slave cylinders
  • Running the clutch hardline through the body
  • Adding the clutch damper
  • Swapping the shifter
  • Adding the clutch pedal and bracket
  • Adding the MT brake pedal
  • Swapping the MT tach gauge
  • Swapping the MT camshafts
  • Swapping the MT valve springs
  • Clipping R4 on the ECU
  • Wiring changes
Doing the full swap gives us a NSX identical to a MT version. However, most people just do the "budget swap":
  • Clutch master and slave cylinders
  • Running a clutch soft line under the body
  • Adding the clutch damper
  • Swapping the shifter
  • Adding the clutch pedal and bracket
  • Adding the MT brake pedal
  • Wiring changes
With the budget swap, you retain the AT ECU maps. You're basically shifting an AT engine with a manual trans. You therefore have to keep the 7,500 rpm limit to protect the engine and are limited to 252 hp. Most people are ok with that.

I did the full swap, plus some other things. You can read about it in my build thread.
 
@Honcho comes thru with gold again. Here's my $0.02 to add for OP's consideration.

There is an upside for doing the swap. You can consider a gearset swap which is probably one of the best mods you can do on an NSX. Most folks with a USDM MT NSX probably wishes they upgraded to some flavor of a JDM gearset (there are a handful of gearing combinations here). So if you're going to go through the trouble of a AT>MT swap I highly recommend you consider a lightweight flywheel/clutch combo and of course, gearing swap. Again, it's one of those.. ."while you're in there" mods.

With that said... if you're concerned about $10-15k variances or even $20-25k variances like you called out above... I'm afraid you're going to have to raise your budget higher especially if you're not doing the work yourself. Not only are parts scarce for this car but so are the shops able and willing to work on them.

Lastly, assuming you go through the mods... there is one aspect of an AT 3.0L that's a rather big con - it is the 7500 rpm limit due to the cams. There's nothing more buzz kill than rowing the gears and having to shift prematurely at 7500 vs. 8200 rpm. It's expensive to swap cams, BUT! if, say, you need to do a motor out service like a Timing Belt, Head Gasket, LMAs, etc.. it *might* make sense to buy different cams with supporting valve train to raise that rpm. Again, that's probably like at least $3-8k depending on the work involved.

My advice FWIW... Keep the car as is. See if you enjoy the chassis enough in AT form before spending the big bucks on an MT swap.
 
Start collecting parts now, It will take you 2-3 years to get most everything you need. Parts are going NLA quickly. Unless Honda is going to fund a Legacy Program, then parts are going to be scarce for the foreseeable future.

I estimate the cost of parts will be US$10k-$15k+. Installation will probably be $5k-$10k. My guess is it will likely cost closer to $25k than not for you.

There are a couple of 5MTs on auctions.yahoo.co.jp right now. If you are serious with the conversion, I recommend you start making arrangements. An AT->MT kit will probably rise in value, so start sooner than later.

I've personally performed the conversion. The AT is a great transmission and is a lot of fun. I got in just before Honda deprecating their parts catalog. I'm not sure I would do it now as it would be a quest...well, maybe I would because I am a bit insane. The AT is a fun car, you aren't missing much.
 
Last edited:
Agree with @RYU and @drew 100%. The AT NSX is still a NSX. It's quite enjoyable and delivers the NSX "specialness" just the same as the manual car. The swap used to be much easier because parts were easier to source. As noted above, you're looking at 2-5 years of waiting and at least $25k. Which is why we're all saying just get a MT or enjoy your AT as-is. :)
 
Thank you all for your input! I plan on keeping the auto in the meantime and enjoying the car as is. If I do end up doing a swap, it will be sometime down the road after I have had my fun with the auto. Part of the reason I would eventually like to have a manual would be not only for the higher RPMs, but also the slight additional HP and ability for the manual transmission to handle higher HP gains with upgrades such as headers, etc.

Unfortunately, I do not think I would be able to do most of the transmission swap myself, so I would likely need to take it to a shop to have the work done if I chose to go through with it. Would any of the above listed have experience and be able to do the swap?

I did recently see a 5-speed transmission with a JDM short gear set for sale for $7k, which I am quite tempted to buy. I’m thinking of buying it now and sitting on it until I make my decision to swap or not, as I could always resell it.
 
Last edited:
Thank you all for your input! I plan on keeping the auto in the meantime and enjoying the car as is. If I do end up doing a swap, it will be sometime down the road after I have had my fun with the auto. Part of the reason I would eventually like to have a manual would be not only for the higher RPMs, but also the slight additional HP and ability for the manual transmission to handle higher HP gains with upgrades such as headers, etc.

Unfortunately, I do not think I would be able to do most of the transmission swap myself, so I would likely need to take it to a shop to have the work done if I chose to go through with it. Would any of the above listed have experience and be able to do the swap?

I did recently see a 5-speed transmission with a JDM short gear set for sale for $7k, which I am quite tempted to buy. I’m thinking of buying it now and sitting on it until I make my decision to swap or not, as I could always resell it.
You are too new of a member to PM but if you get your post count up, send me a PM. I will be selling an AT- MT conversion in a few months.
 
You are too new of a member to PM but if you get your post count up, send me a PM. I will be selling an AT- MT conversion in a few months.
Oh I might be interested, but it might take me a while to get my post count up - any details you could provide in the meantime?
 
Oh I might be interested, but it might take me a while to get my post count up - any details you could provide in the meantime?

Work hard. Save money.

:devilish:

And enjoy your automatic trans NSX. We own two.

And you can reply, to add to you post count. ✅
 
Hello all,

I am a longtime lurker on these threads and a first-time poster as a new 1991 NSX owner. I’ve wanted an NSX as my dream car ever since high school and have recently been able to finally get my hands on one for a good price, albeit an automatic rather than a manual. I was able to find an auto NSX that was virtually all stock and still runs relatively great despite its age and about 100k mileage (there was a mileage/odometer discrepancy, which also contributed to the low price). Nevertheless, it is a great car and driving it has been incredibly fun, even with the auto transmission. After driving it though, I have come to the realization that I would ultimately like to have a manual NSX and I now have a dilemma that I would like to ask for advice from those with experience in this forum.

Should I keep my existing auto NSX and eventually swap the transmission to a manual when the auto transmission starts to fail/need maintenance? Or should I sell my auto NSX and try to buy a manual NSX down the road in a few years? Let me preface this with the fact that I was able to get my auto NSX for a great price; at least $15-20k+ lower than a comparable manual (though at the prices I have been seeing lately, probably closer to $25-30k+ less). I also plan to keep and enjoy driving this car as an automatic for the next couple of years or so as it runs relatively great and is a lot of fun, so this would be a future project that I could save up for/work on a little at a time. Since I am planning on keeping it for a while, I will perform any maintenance/upgrades that it may need, so this would also seem to be more of a sunk cost to me and incentivize me to swap the transmission since I will be already investing time/money into the car (TB/WP service was already done, but the car needs new wheels/tires, ABS/power-steering light is on, would change out stereo/lights eventually, maybe change the paint color, etc.) I probably would not touch the power-steering though, as it isn’t that much of an issue for me.

From those of you who have swapped your automatic to a manual, how was the process (length, difficulty, total price, etc.) and how well has it held up after the swap? Does it drive the same as a stock manual? How would the value of the car hold up, if I needed to sell the car in the future(this is my dream car so I have no plans to ever sell, but would still like to make sure that I am not bringing down the value too much)? Would the fact that it was swapped to a manual still allow it to retain the market value of a manual NSX, or would that bring it down significantly?

I am located in the Bay Area (East Bay) and would also like to know some reputable NSX shops close by to get maintenance/work done (preferably near Fremont/San Jose if possible). Also, would any of these shops be able to properly take on the task of performing a transmission swap?

Thank you all in advance!
Sell yours quick and get a manual transmission car right away. The price spread will be more like $50,000 in 5 years. In 10 years a clean under 25k mile, manual will be selling for over $200,000. Trust me I have been investing in sports cars for 35 years and the manual Trans. NSX’s (Red) will be selling for over 400k in 20+ years. Auto. Trans cars will not do very well.
 
Back
Top