G50/50 convert question

[TurboKraft]

There's more to it than that, but if you have machining facilities at your disposal, it won't be too difficult.

[Tippy]

Oh really? Bummer. Can you explain what it'd be?

[IMR-Merlin]

I keep hearing this debate about not cutting the torsion tube and I always think notching the tube is better.

Why go the shortened bell housing route vs torsion tube notching? These cars are rear biased as it is, so wouldn't notching the torsion tube bring the whole trans 1.5" more forward, thus help bring some weight forward?

Here are a few pics from my conversion.

[Tippy]

After seeing one notched being such little work, it'd be silly to spend so much on shortening.

[Rodsrsr]

It looks like a lot of work to me and its probably a track build. He cut out the whole rear section of the interior to make room for the tie in's. Pick your poison. If you dont have the fab skills to do all the necessary work, it will will probably cost the same or more than just having the unit shortened. Plus with a short G50, if you ever need to swap tubs, (wreck your car, just want a change, ect..) your complete drive train will be a bolt in job to your next project.

[IMR-Merlin]

Originally Posted by Rodsrsr

It looks like a lot of work to me and its probably a track build. He cut out the whole rear section of the interior to make room for the tie in's. Pick your poison. If you dont have the fab skills to do all the necessary work, it will will probably cost the same or more than just having the unit shortened. Plus with a short G50, if you ever need to swap tubs, (wreck your car, just want a change, ect..) your complete drive train will be a bolt in job to your next project.

False assumption on a few items. I didn't need the rear seat so I used lighter gauge steel and freed up some space. Plus I wanted to move the coil packs forward and have an access panel to get to them for diagnostics if needed. The car will be a street/track car. You could do a bunch of different tie in's that keep the factor sheet metal.

Like you said, pick your poison. I did it for weight transfer, plus if I ever blow the G50, all I have to do is buy another one and bolt it in. Not rebuild/swap bell housings and input shaft (provided they survived).

[Tippy]

It looks like a lot of work to me and its probably a track build. He cut out the whole rear section of the interior to make room for the tie in's. Pick your poison. If you dont have the fab skills to do all the necessary work, it will will probably cost the same or more than just having the unit shortened. Plus with a short G50, if you ever need to swap tubs, (wreck your car, just want a change, ect..) your complete drive train will be a bolt in job to your next project.

It looks like he only needed to notch the torsion tube. Am I missing something?

[IMR-Merlin]

Originally Posted by Tippy

It looks like he only needed to notch the torsion tube. Am I missing something?

You are correct. I added a bunch more bracing to take some of the flex that the factory set up has. I am running a EFI engine with 420 RWHP with some other plans for the future, so I wanted to eliminate as much toe and camber change from flex under power as possible, so I erred on the side of caution and over built a bit.

[Tippy]

Then my original post stands. Hack the tube, seems easiest.

[IMR-Merlin]

You can always look for a G50 donor car like I did. I bought mine at auction for $5500 and had it shipped from Seattle to NH for $1300. $6800 for a complete (hit in the nose) 87 with a G50/01. I sold the engine for $4000 and other parts for $1500. By the time I finish parting it out I will have the G50 for free. This way you get the trans, pedals, slave cylinder AND if you want to do the work, a complete G50 torsion tube.

I would suggest going over to the racing and auto cross forum for anymore questions on this. It's a bit slower than the turbocharging forum, but the guys over there have done this a lot.

Like others have said, it's apick your poison type of thing.

I picked the one that I could do myself, the one that would move more weight forward, and god forbid anything catastrophic happen to the G50, all I have to do is source another trans and bolt my billet side cover on it.

The other comments are valid, but if you crash your 930 so much that you need to swap tubs, chances are you are doing far more damage to other parts and bits as well.

Brendon

[vinyl_tien]

Thanks Turbokraft and IMR-Merlin
I just wonder how much reinforce do I need after I cut the TB, my car will be for street only.

[Iciclehead]

I am well into the process of doing this for street on my '89 to fit a six speed, no issues with fitment and certainly the little bit of torsion tube I cut out will not affect its rigidity at all.

Here is the thread....

Fitting 6 speed G50 to '89 Carrera

Dennis

[totle]

As I understand you can not notch/cut the torsion tube if you want to still use torsion bars without adding the center tube from a 87- chassis.
When they added G50 transmission in 87, they also added shorter torsion bars. On pre- 87, the torsion bars are longer and will meet in the center of the tube (more or less)

[Iciclehead]

Originally Posted by totle

As I understand you can not notch/cut the torsion tube if you want to still use torsion bars without adding the center tube from a 87- chassis.
When they added G50 transmission in 87, they also added shorter torsion bars. On pre- 87, the torsion bars are longer and will meet in the center of the tube (more or less)

I think that the torsion bars are similar length, but they extend further outward....I recall that the spring plates have longer tubes on the later car. I know that the splines are different in the 87- cars, so you need the right ones.

I have no issue notching the tube on my '89 as you can see from the thread. When I looke at it, there is bracing that ties the tube to the chassis close by, the tube itself is about 6mm steel and of course, given you seal it off with material, it is a tube and fairly stiff.

I do wonder why the factory did not make the tube slimmer considering the hassles that they had with moving the engine back, but then again, it is cast steel and they may have had size restrictions in manufacturing that part.

Dennis

[IMR-Merlin]

Originally Posted by totle

As I understand you can not notch/cut the torsion tube if you want to still use torsion bars without adding the center tube from a 87- chassis.
When they added G50 transmission in 87, they also added shorter torsion bars. On pre- 87, the torsion bars are longer and will meet in the center of the tube (more or less)

Correct, you either need the tube (or center) from a G50 car or convert to coil over.

Originally Posted by Iciclehead

I think that the torsion bars are similar length, but they extend further outward....I recall that the spring plates have longer tubes on the later car. I know that the splines are different in the 87- cars, so you need the right ones.

I have no issue notching the tube on my '89 as you can see from the thread. When I looke at it, there is bracing that ties the tube to the chassis close by, the tube itself is about 6mm steel and of course, given you seal it off with material, it is a tube and fairly stiff.

I do wonder why the factory did not make the tube slimmer considering the hassles that they had with moving the engine back, but then again, it is cast steel and they may have had size restrictions in manufacturing that part.

Dennis

The G50 car's tie in the torsion tube a bit differently also. I have my donor car with the engine and trans out if you want, I can take some pics of it.

[Iciclehead]

Originally Posted by IMR-Merlin

The G50 car's tie in the torsion tube a bit differently also. I have my donor car with the engine and trans out if you want, I can take some pics of it.

Thanks for the offer, but my car is still in a state of total disassembly (as per my thread on it). I also have a '75 that is quite different in this area as per the other comments on the thread.

Here is a pic I found somwhere on the web that shows the later tube...



Dennis

[IMR-Merlin]

Originally Posted by Iciclehead

Thanks for the offer, but my car is still in a state of total disassembly (as per my thread on it). I also have a '75 that is quite different in this area as per the other comments on the thread.

Here is a pic I found somwhere on the web that shows the later tube...



Dennis

I was going to show people here how it was tied into the current tub. I saw your build when I was looking for trans options for my 930 build. Nice work!!

[Rodsrsr]

So if I'm understanding this correctly you basically have 3 options;

#1 notch the tube which means ditching the T-bars so you'll need to tie everything in for coil-overs. This is the fuzzy part for me. What all needs to be tied in for this on a street car?

#2 Graft in a torsion tube center piece from a G50 donor car so you can retain T-bars, although you'll need the shorter set from the donor car as well.

#3 Short G50 $$$ no mods to tub but you need custom clutch and some other components. Not sure if doing option 1 or 2 leaves you with dual mass clutch?

[IMR-Merlin]

Originally Posted by Rodsrsr

So if I'm understanding this correctly you basically have 3 options;

#1 notch the tube which means ditching the T-bars so you'll need to tie everything in for coil-overs. This is the fuzzy part for me. What all needs to be tied in for this on a street car?

#2 Graft in a torsion tube center piece from a G50 donor car so you can retain T-bars, although you'll need the shorter set from the donor car as well.

#3 Short G50 $$$ no mods to tub but you need custom clutch and some other components. Not sure if doing option 1 or 2 leaves you with dual mass clutch?

#1 you can rebuild your center section as I did and not brace. Use all stock G50 parts

#2 tube and bars from donor car would be needed. I read the splines are different ( not 100% sure), Use all stock G50 parts

#3 you need to shorten the bell housing and input shaft, not sure on the clutch.

[mamut]

You guys are over complicating things!
First option, both are expensive:
Shorten the tranny.
Get rid of the tube, install coil overs.
I like the later., why?, you can have a really nice handling car at the same time you do the conversion..
Stef.