1999 RS-GSX

[Masonjr]

This is the Build Thread for 1999 RS-GSX. Reply below.

 

[pauleyman]

This is the Build Thread for 1999 RS-GSX. Reply below.

I am absolutely not trying to discourage you...however. I've been around these DSMs for 33 years. You would be WAY better off starting with a 4g63 chassis. Unless you are completely disassembling the car anyway and you happen to be a skilled fabricator there are just too many differences. You will spend an enormous amount of money and time unnecessarily since the 4g63 chassis already exists.

 

[Masonjr]

I am absolutely not trying to discourage you...however. I've been around these DSMs for 33 years. You would be WAY better off starting with a 4g63 chassis. Unless you are completely disassembling the car anyway and you happen to be a skilled fabricator there are just too many differences. You will spend an enormous amount of money and time unnecessarily since the 4g63 chassis already exists.

Trust me I’ve heard it time and time again how not worth it it is. I’m using a 4g63 from an evo 8 which lines up pretty well with the motor mounts. The tranny mount brackets needs to be moved forward and down a bit but that’s the majority of the fabrication. I’m getting lots of custom parts and fabricated parts to do this swap and avoid having to chop things up too severely. The Evo 5 RS finally gear ratio is as close to the GSX auto LSD as it gets and is safe to run. I’ve spent upwards of 4 years doing research on this project. And the price goes up and up and it’s at the point where I don’t budget this build anymore. I want to do it right so I don’t have to do anything else to it. I’m going as fully built as it gets. Every nut bolt and stew will be turned. If the price of this can’t deter me nothing will I’m not one of those say it talk about it people. I’m a mention it kinda and actually do it. My current struggle is getting the trans and transfer case

 

[pauleyman]

Trust me I’ve heard it time and time again how not worth it it is. I’m using a 4g63 from an evo 8 which lines up pretty well with the motor mounts. The tranny mount brackets needs to be moved forward and down a bit but that’s the majority of the fabrication. I’m getting lots of custom parts and fabricated parts to do this swap and avoid having to chop things up too severely. The Evo 5 RS finally gear ratio is as close to the GSX auto LSD as it gets and is safe to run. I’ve spent upwards of 4 years doing research on this project. And the price goes up and up and it’s at the point where I don’t budget this build anymore. I want to do it right so I don’t have to do anything else to it. I’m going as fully built as it gets. Every nut bolt and stew will be turned. If the price of this can’t deter me nothing will I’m not one of those say it talk about it people. I’m a mention it kinda and actually do it. My current struggle is getting the trans and transfer case

By all means then, full steam ahead. For what its worth you mentioned gear ratios as "close enough" I would double check your math. They need to match. Since you're fabricating anyway why not use the evo rear diff.

 

[Masonjr]

By all means then, full steam ahead. For what its worth you mentioned gear ratios as "close enough" I would double check your math. They need to match. Since you're fabricating anyway why not use the evo rear diff.

The final ratios for the transfer case I believe is 3.312 and I believe the rear did is 3.307 and what I’ve read and talked with trans guys is it shouldn’t cause ant significant problems. My friend Miguel that completed the Evo swap uses the diff out of an Evo 4 RS I believe he said which is the same ratio and his car is doing great. It’s definitely something I want to get more clarity on but so far that’s my only uncertainty about the project. The other issue I’m having is figuring out how to wire up the A/C. I need to basically wire up an independent A/C harness.

 

[Capt Obvious]

Worst case scenario, the gear ratio differences can be negated with staggered tire sizes.

On the 993 and 996 Porsche 911s (which use a viscous center diff) Porsche purposely chose tire heights that were a small percentage off front to rear (fronts slightly taller) to "load" the differential and heat the viscous fluid so it would send more power to the front wheels as your speed increased.

 

[Masonjr]

Worst case scenario, the gear ratio differences can be negated with staggered tire sizes.

On the 993 and 996 Porsche 911s (which use a viscous center diff) Porsche purposely chose tire heights that were a small percentage off front to rear (fronts slightly taller) to "load" the differential and heat the viscous fluid so it would send more power to the front wheels as your speed increased.

This is good info. For such a small difference do you have any recommendations for the difference in tire size?

 

[Capt Obvious]

Realistically, the difference between 3.312 and 3.307 is so small that it's inconsequential. You're talking like 2-3 tire rotations over the course of a mile. Uneven tire wear or air pressure will cause more of a rotational discrepancy than that.

 

[Masonjr]

Realistically, the difference between 3.312 and 3.307 is so small that it's inconsequential. You're talking like 2-3 tire rotations over the course of a mile. Uneven tire wear or air pressure will cause more of a rotational discrepancy than that.

So essentially it should have no issues with a square setup

 

[Capt Obvious]

I would not worry about it if it were my car.