G-50 tall 5th gear

[H Lee]

I am a newby and my first challenge is to find instructions on how to swap out the factory 5th gear on a g-50 (1988) for a taller set. The GT40 (partially assembled) kit we just bought came with the tranny and a set of G 50-50 5th gears along with the uninstalled Quaife differential. I have instructions (and some experience on the 915)with the Quaife, but have never opened a G50. Does anyone know where I can get detailed instructions on swapping out the original gears for the taller G50-50 set? Any assistance will be greatly appreciated.
This will be my initial project while we sort through everything to see what has been done and what has not. Many more questions to follow, I am sure.

 

[Peter Delaney]

Hi Mate, Unfortunately, I can't help with instructions

But before you start, have you looked at a higher ratio ring & pinion set ?

The reason I ask is that I had a tall 5th gear set installed in my G50 & I wish I had gone the R&P route. With the standard diff & lower gears, you could pull a stump out of the ground with 1st, 2nd is where I start most of the time, 3rd & 4th are fine - nice & close. But the jump from 4th to 5th is a big one & its just at that point where its annoying at suburban speed limits of 60kph - not really comfortable in either 4th or 5th !

If you are interested, I have an Excel s/s which allows you to play with diff & gear ratios to plot revs vs speed in each gear. Let me know if you want a copy.

Kind Regards,

Peter D.

 

[Erik]

Hello,

I would recommend that if you are going to change out the 5th gear that you also change the 4th to a taller ration as well. If you do not do this you will find the drop from 4th to 5th to be quite large and possibly not what you were thinking.

A good change would be 0.96 in 4th gear and 0.65 in 5th gear. PM me if you need help with this, I am happy to give you some options. As to the actual changing out of the gears, I would not say that it is the hardest of things to do, but you do need some specialized tools to get the gears to release, and you will also need new nuts for the pinion and mainshaft, as these are single use only.

Again happy to help if you have more questions,

Erik Johnson
GBox Performance
(303) 440-8899 work

 

[Jack]

There are several reasons that I choose the 930 with LSD.
The gear ratio's are almost perfect for the V-8, it will stand a great amount of torque,
and is relatively lightweight. A 4 speed that works very well.

 

[Darrell]

I fitted a taller ring and pinion in my car and it completly changed the car. Now 1st gear is usable and the car cruises great on the open road. Performance was not realy effected as 1st was just a stump puller and i never used it.

Darrell DRB#46
LS1 G50

 

[Erik]

I would agree that a ring and pinion change to perhaps 3.10 would be one of the better options, however it is not a cheap one, as the part is rather expensive, as is the installation to install it.

I does however address the entire gear stack and make it far better suited to the V8 power.

Erik Johnson
GBox Performance
(303) 440-8899 work

 

[EGLITOM]

Hey H


All of the above stated is correct to some degree. But generally correct gearing is related to much more factors.

• Driving purpose. Where and how the car will be driven . cruising versus performance oriented driving
• engine choice: What is the working and most used rpm range of your engine
• Tire Size. Don´t unterestimate the influence of your tire size on you total gearing ratio

Also G50 is a very general term. What G50 is it what you have. There are lot of differences in gearing between the different types. Here are the ratios of them all
Except the G5005 ( US version) all of them have a 3,44 final drive ratio
The most desirable ones in terms of good stock ratios is the G50/02 &G50/04 ( swiss version it has the tallest 1st and nice stacked 3rd to 5th) and the G5005 because of the tall r&p.
G50/00 3.5 2.059 1.409 1.074 0.861 (after 1988 0.868)
G50/01 3.5 2.059 1.409 1.125 0.889 (after 1988 0.892)
G50/02 3.154 1.895 1.333 1.036 0.861 (after 1988 0.868)
G50/03 3.5 2.059 1.407 1.086 0.868
G50/04 3.154 1.895 1.333 1.029 0.868
G50/05 3.5 2.059 1.407 1.086 0.868 Final drive ratio: 3.333:1
G50/10 3.154 1.895 1.407 1.086 0.868
G50/50 3.154 1.789 1.269 0.967 0.756 Beefier internals, differential cover, and case
G50/52 3.154 1.789 1.269 0.967 0.756

I have attached a gear ratio chart with some different versions. i included a stock G5003 , -04 , -05 also all of them modfied with the -50 5th and one chart of my modified G5005 which has a taller 1st and 2nd. You can set your max shift RPM in cell "K7" ( currently set to my shift rpm of 7200), You can also see than the RPM drop in cells "J27 to J30"
Please put in your tire size in cells "Q26 to S26".

For me personaly the drop from 1st to second is to big, so a taller 1st is desired ( except you have already a G5004/02).

In my modified box i have used a 1st gear complete new mainshaft from Quaife and a 2nd gear set from Guard transmission. Im also using a Quaife ATB diff. All of this works great. is nice to shift and drive. The tall first is no issue at all with my still organic clutch friction plate ( if one decides for a sinter friction disc it will be more difficult in heavy dail traffic).

You see there is a lot more to it. play with the numbers in the charts and find the best solution for yourself

HAve fun ( i had to split the chart in two files because of the size restriction of the forum)

TOM