G50 Transmission Question
#1
8th Gear
Thread Starter
Join Date: Oct 2007
Location: Long Grove, IL
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Hey everyone. I'm in the very beginning stages of the search for my dream car (84-87 carrera coupe). I'm brand new to this forum, and I have a lot to read and learn. I'm really excited to head down this journey! One of my first questions is when did the G50 transmission come out? What I've read so far is that it is desirable, but not sure what model year it was introduced.
Thanks in advance for your help.
Thanks in advance for your help.
#4
Addict
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
As you start your search for the perfect car and you find a G50 tranny don't be scared off by it if it is cold out. My rebuild now has 9,000 miles on it and it is very stiff when it is cold. after about 15 minutes or so it warms up and is a delight to drive. It tells you that you found the gear and then that you have it in. I have a weekends only cab that is very easy to jump into and go. The tranny just takes a little love.
#6
Instructor
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
I have an '89 coupe with the G50 - all original. I notice that that the transmission is stiffer until warmed up. It's not difficult to shift, but it definitely gets smoother once it's warmed up.
#7
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
All I see most people post on gear oil is a brand called Swepco.
Seems there are a few unhappy people using mobil1, great cold shifting terrible hot shifting in their 911's.
If you like Swepco, which particular weight and type do you like?
Thanks
Trending Topics
#8
Intermediate
Join Date: Oct 2003
Location: Near Philly, Pa.
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
I've been out driving various Porsches again in search for a "new" 911 and have been in a well maintained, low mileage '88 with a G-50 and, call me crazy, but I really prefer the 915. Lots more character, not hard to drive if you know what you're doing and you know you're in a real 911. I guess I didn't like the light pedal of the hydraulic clutch release and the lack of feedback from the modern synchros. But I drive an old 911 because I love the feel of it--there are faster family sedans on the road now, at least in a straight line.
As to fluid, people swear by Swepco 201 in the 915 transmission. 203 is also available, it's 201 but has molybdenum added for additional wear protection but even the Swepco technical people will tell you 203is overkill for a street driven Porsche. (I know, I called them and the phrase "belt and suspenders" came to mind.) That being said I used 203 in my '86 and found it improved my shifting, maybe only because it might have been the first change since new, but not dramatically (still couldn't shift into first if moving significantly)--I was going to switch to 201 so see if the absence of moly and, I assume, slightly increased friction in the 201 might help the synchros work better. (Unfortunately I was rear ended and totalled Monday so I can't complete the experiment. That's why I'm getting to drive other people's Porsches.) The G-50, however, is supposed to appreciate modern synthetic lubricants. Swepco, despite it's many miraculous qualities--it is claimed to be the Lourdes water of the 915, is refined dino.
Good luck and enjoy your search.
As to fluid, people swear by Swepco 201 in the 915 transmission. 203 is also available, it's 201 but has molybdenum added for additional wear protection but even the Swepco technical people will tell you 203is overkill for a street driven Porsche. (I know, I called them and the phrase "belt and suspenders" came to mind.) That being said I used 203 in my '86 and found it improved my shifting, maybe only because it might have been the first change since new, but not dramatically (still couldn't shift into first if moving significantly)--I was going to switch to 201 so see if the absence of moly and, I assume, slightly increased friction in the 201 might help the synchros work better. (Unfortunately I was rear ended and totalled Monday so I can't complete the experiment. That's why I'm getting to drive other people's Porsches.) The G-50, however, is supposed to appreciate modern synthetic lubricants. Swepco, despite it's many miraculous qualities--it is claimed to be the Lourdes water of the 915, is refined dino.
Good luck and enjoy your search.
#9
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
....have been in a well maintained, low mileage '88 with a G-50 and, call me crazy, but I really prefer the 915. Lots more character, not hard to drive if you know what you're doing and you know you're in a real 911. I guess I didn't like the light pedal of the hydraulic clutch release and the lack of feedback from the modern synchros.
#10
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Mine is not stiff but definitely feel some friction on the first couple mins, on 1st and 2nd gears. After it's warm up, it's much smoother.
As you start your search for the perfect car and you find a G50 tranny don't be scared off by it if it is cold out. My rebuild now has 9,000 miles on it and it is very stiff when it is cold. after about 15 minutes or so it warms up and is a delight to drive. It tells you that you found the gear and then that you have it in. I have a weekends only cab that is very easy to jump into and go. The tranny just takes a little love.
#11
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
My '89's G50 is a bit mildly stiff when very cold,..but quickly heats up to butter!!!
When she is cold (and stationary), I'll drop her into 3rd before placing her in first...makes a difference insofar as friction going into 1st..(someone here had told me to do that when she's cold..)
I prefer my G50 over the 915....don't care much about this weight thing.
Best,
Doyle
When she is cold (and stationary), I'll drop her into 3rd before placing her in first...makes a difference insofar as friction going into 1st..(someone here had told me to do that when she's cold..)
I prefer my G50 over the 915....don't care much about this weight thing.
Best,
Doyle
#12
Drifting
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Saved from previous 915 vs g-50 weight mumbo jumbo.
G-50 vs 915 Transmission
as far as tight cold - make sure you have a good synthetic lube - I prefer the high grade Mobile one gear lube - not the stuff you get at the local auto parts place.
G-50 vs 915 Transmission
FWIW, the difference G50 vs 915 is 45lbs, but that includes everything flywheel forwards. The bare trannies are about 27lbs. You can fairly easily save 20lbs on the G50 by going for a lightweight aluminium pressure plate, a spring centred clutch and L/W flywheel. Now you are only 25lbs difference and you get the benefit of an engine that revs much quicker between gears and has less reciprocating mass for better acceleration. That's not to say you can't save some weight on a 915 as well, but you get the idea.
Richard
Richard
I have weighed the late 80's G50 and the aluminum 915 and there is 20.5 lbs difference stock trans to stock trans. I figured by the time I beef up a 915 and add a cooler I would only have about a 10 lb savings, not worth sacrificing the reliability of the G50 in my opinion. My G50 is bullet proof with out a cooler and I have been very happy with the decision. There is another 10 lbs savings if you use an older mag case 915 but that would not hold up to a 3.8 RSR motor from what I hear.
Let's look at this a little closer. The weight of a filled 915 RoW version 915/67 with cooler is approximately 60 kg (132 lbs). The cooler weighs almost nothing (I can testify to this because I've cleaned a number of them), so let's call the USA 915/68 at 130 lbs. The weight of a filled RoW G 50 version 950/00 is 66 kg (146 lbs), which is virtually identical to the USA version 950/01. So we have a weight difference between the two transmissions of 16 pounds.
The 915 flywheel weighs 12 lbs, and so does the G 50 flywheel, so that's even.
The stock 915 clutch weighs 18 lbs, the G 50 clutch weighs 29 lbs. So, in total, the G 50 package is approximately 27 lbs heavier, which was offset (in 1986) by an increase in rear torsion bar size from 24.1mm to 25mm. Something else comes into play here that contributes to the 915 car "feeling quicker" to some drivers. Back in the day of Hemi-Cudas, 427 Vettes, etc., the ticket to really quick quarter mile times was having a "short", 4.11 rear end (final drive) ratio, or an even shorter 4.56 ratio. Of course, the big compromise with a short ratio was having to run at much higher revs at freeway speeds. Cars with a taller, aka longer, 3.00, or 3.30 rear end (ring & pinion ratio) just wouldn't come out of the hole as quick, and the race was usually over in 2nd gear. In 1974, 911s were fitted with a 7:31 ring & pinion, which is a final drive ratio of 4.43 (remember, the bigger the number the shorter the ratio). Later SCs and early Carreras w/915s had an 8:31 (3.88) final drive ratio, BUT, G 50s are fitted with a 9:31 (3.44) final drive ratio. Yes, the factory fitted all new, "shorter" ratios to 1st-5th to try and make up for it, but, while striving for better mileage and reliability, couldn't overcome that "longer" ring and pinion, which can make, combined with the extra pounds, a G 50 car feel more sluggish than a 915 car. A lightweight clutch will help the G 50 car, but on a road course there should be very little difference between the two because the rpm drop between second and third, between third and fourth, and between fourth and fifth, is very similar when comparing a 915 to a G 50. Yes, the 915, in some situations, will "feel" quicker, but can it generate quicker lap times on a road racing course? I doubt it.
The 915 flywheel weighs 12 lbs, and so does the G 50 flywheel, so that's even.
The stock 915 clutch weighs 18 lbs, the G 50 clutch weighs 29 lbs. So, in total, the G 50 package is approximately 27 lbs heavier, which was offset (in 1986) by an increase in rear torsion bar size from 24.1mm to 25mm. Something else comes into play here that contributes to the 915 car "feeling quicker" to some drivers. Back in the day of Hemi-Cudas, 427 Vettes, etc., the ticket to really quick quarter mile times was having a "short", 4.11 rear end (final drive) ratio, or an even shorter 4.56 ratio. Of course, the big compromise with a short ratio was having to run at much higher revs at freeway speeds. Cars with a taller, aka longer, 3.00, or 3.30 rear end (ring & pinion ratio) just wouldn't come out of the hole as quick, and the race was usually over in 2nd gear. In 1974, 911s were fitted with a 7:31 ring & pinion, which is a final drive ratio of 4.43 (remember, the bigger the number the shorter the ratio). Later SCs and early Carreras w/915s had an 8:31 (3.88) final drive ratio, BUT, G 50s are fitted with a 9:31 (3.44) final drive ratio. Yes, the factory fitted all new, "shorter" ratios to 1st-5th to try and make up for it, but, while striving for better mileage and reliability, couldn't overcome that "longer" ring and pinion, which can make, combined with the extra pounds, a G 50 car feel more sluggish than a 915 car. A lightweight clutch will help the G 50 car, but on a road course there should be very little difference between the two because the rpm drop between second and third, between third and fourth, and between fourth and fifth, is very similar when comparing a 915 to a G 50. Yes, the 915, in some situations, will "feel" quicker, but can it generate quicker lap times on a road racing course? I doubt it.
#13
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
I'll add that you'd be nuts to pass over an 84-86 because it has a 915 tranny. Sure, the G50 is an improvement, but there are just a FEW cars with 915's out there that run and drive just fine.
#15
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
My G50 is also persnickity when cold. It resists going into 2nd. It was that way with whatever oil was in it when I bought it, and with the new Mobil Delvac I put in.
When it's hot, no issues.
I only test drove one 915 tranny, but it wasn't for me. Throws were long and I didn't like the uncertain "am I really in gear?" feeling when I shifted.
When it's hot, no issues.
I only test drove one 915 tranny, but it wasn't for me. Throws were long and I didn't like the uncertain "am I really in gear?" feeling when I shifted.