Contemplating 930 tranny to G50 conversion.

David · David's Garage

I've done a search without much success on a tech article on the G50 conversion. I have a '79 930 that I'm looking to convert. I'm wondering what parts are needed at what price. Here's what I've come up with, could someone add to and/or correct this list.

Parts:
G50 - $1500
G50 clutch peddle assembly - $200 (guess)
Rear coil overs - $1000 (guess)
Clutch (what type?)
New flywheel?
New inner CV joints?
Shift linkage - $200 (guess)

Labor: (in addition to installation)
Remove inner torsion tubes
Reinforce tranny tube area
Shorten bell housing (24mm?)
Shorten main shaft?
Gusset rear shock tower

Thanks for any help!

David · David's Garage

I just found this article/ad for the G50 conversion. It's got some good info, but I'm a 99% DYI'r so I'm looking for junk yard prices if anyone has experience.
http://www.bodymotion.com/Core/911_transmission_upgrades.htm

ChrisBennet · ChrisBennet's Garage

Stange that they advocate a torque biasing differention (Quaif or Torsen) for track work...
-Chris

dean · 09-20-2003, 05:34 PM

I installed a G50 in my SC last winter. I think it cost me about $4k total. I did all the work myself except machining the tranny. I sent that to Protechnic in TX. That cost $450 plus shipping. If you shorten your G50 I don't think you have to do the coilovers. If you shorten the tranny you would use an early 930 clutch.

It is a fair amount of work and money but it is worth it IMO.

beepbeep · 09-21-2003, 03:14 AM

You don't need new axles as far as i know.

David · David's Garage

Thanks for the info, Blown. I went by Protecnic for the first time the other day. I talked with Sam S. for quite a while and was impressed with his knowledge and the machine work he showed me (very cool slide valves for NA cars). I work in a machine shop but I'm inclined to send the machine work to Sam. Blown, would you mind listing all the parts you had to replace or modify and their prices. I would be very grateful and I would think anyone else doing the conversion would be also.

As for the coilovers, I need to replace my rear shocks and I'd like a little stiffer torsion bar. So I figure for not much more money I could get coilovers.

dean · 09-21-2003, 06:50 AM

As far a going to coil overs I think you have to stiffen up the rear towers and engine compartment if you go to them. I got a quote from someone that they would be between $ 600 and $1000.

I don't know if I can remember all the parts I needed. I will try.

Tranny $1400
Machining $550
Shifter $250
Pedal ass $150
Master cyl res $50
Hyd line $150
Axles $400
Clutch $750
Clutch fork and slave $150

That is all I can remember now.

Sam at Protechnic did a great job. Fast and accurate

I also recomend KEP for the clutch. Brett was very helpful. I got a stock 930 clutch but next time I will need the KEP modifyed one.

Also there are a few different G50''s. The G50/50 is the one for high hp. I guess it is hard to find and more expensive. I have a regular G50 in mine. I also heard that Guard Transmission is going to do a 5 speed conversion for the 930. But it has been a few years and nothing has progressed. So I wouldn't count on that.

Have fun

350HP930 · 09-21-2003, 06:58 AM

If you are just displeased with your gearing it would be a lot cheaper to change the ring and pinion and/or gears in your 930.

I bought the 8:39 R&P from Andial to give my 930 a bit more get up and go from a dead stop.

David · David's Garage

Blown, what was different about the axles and how does the clutch hold up to your turbo power? I've been planning to go with a Centerforce clutch, but they're more than twice the cost of others. I understand you get what you pay for, but twice as much. (?) I asked Sam about the G50/50 and he didn't think it was worth it. He said he has a 600+ HP turbo car using the G50 with no problem.

David · David's Garage

350HP930, what RPM are you turning on the highway?

350HP930 · 09-21-2003, 07:11 AM

60 MPH used to be 2K RPM.

The new gearing should bump that up to about 2,400 RPMs.

In more practical terms the R&P brings the top end gearing down from around 200 MPH to around 160 MPH and will improve the first gear launch and getting up to speed dramatically.

I will also give me the ability to use 2nd and 3rd gear more often when I'm auto-xing.

masraum · 09-21-2003, 08:13 AM

I believe if you look up the threads on building Jacks BBII you will find what they did to the chassis to allow for the extra stresses of the coilovers on the top mounts. From what I remember it was a little welding, but not as much as you might expect.

Wow, in a turbo you are using 3rd during autox. Those must be pretty big courses.

350HP930 · 09-21-2003, 08:21 AM

Yup, the PCA and the SCCA have some fast events down here every now and then.

Here is a map of one of my favorites that is located in Gainesville.

David · David's Garage

I did one SCCA autox with the stock gearing, I tried 2nd and it was way to tall. I just kept it in 1st and reved the crap out of it. I got comments ranging from "it's good to see someone actually drive one of those like it's meant to be driven" to "did you know your car throws flames out both exhausts?!" I realize the car's not meant for autox and I sure won't be doing any more until the gearing is changed.

So the question is: whether to change gearing in the 930 box or get a G50. I need a new clutch either way so that's a wash and I need new rear shocks and torsion bars, so the coil overs are a wash. Hum, what to do?

dean · 09-21-2003, 02:41 PM

I needed new axles because the tranny flanges are different on a 915. I think my clutch is not holding up very well. I think it has worn out alot but I am not sure. The stock clutch is good for about 370 ft lbs and I think that is just about what I have. So in 4000 mile the clutch seems worn out. I will find out this winter when I take the motor out. How much power do you have. I would recomend the modifyed PP that KEP sells over the Centerforce clutch.

beepbeep · 09-21-2003, 03:19 PM

I know that G50/52 output flange has same diameter as 930 Cv's = 108mm. I also know people who converted their 930 to G50/52 and 3.6TT and still run 930 CV's/axles (actually he sheared a few, car has 750+ HP)...

So answer to axle-question is: no , you don't need new axles.

We are in same process right now with our project-car as we are converting SC to 930 tranny and coilovers.

We found out that Carrera axles (also 108mm) fit 930 flange...

RoninLB · 09-21-2003, 05:29 PM

Quote:

Originally posted by Blown
I I think my clutch is not holding up very well. I would recomend the modifyed PP that KEP sells over the Centerforce clutch.

I love the heavy duty humble attitude..
If it's good enough for Dean, it's good enough for me.. these humble insights get the copy and paste for permanent files...Ron

dean · 09-21-2003, 08:41 PM

Hey Ron,
I'll tell you why I like them. When I needed to shorten my G50, I called around to get the dimensions for the machineing. KEP helped me out with no attitude. Plus they do good work.

RoninLB · 09-21-2003, 09:33 PM

Quote:

Originally posted by Blown
Hey Ron,
KEP helped me out with no attitude.

copy and paste, LOL, LOL...............Ron

David · David's Garage

I don't have the dyno numbers in front of me, but I'd imagine I'm over 400ft-lbs at the rear wheels. Didn't the 930 have close to 400 ft-lbs at the flywheel stock? I guess I'll need a stronger clutch.

Here's a new wrinkle, I was looking at some gearing charts for the 930 and the G50 and it looks like top gear is significantly lower in the G50. When you adjust the ring & pinion to get the same top gear gearing, first gear is not that far off.

EDIT: I checked on the torque and hp. A stock 79 US 930 is 265 HP and 291 ft-lb at the crank. Mine is 345 HP and 337 ft-lb at the rear wheels.