GS tranny in a GT750 box

[tz375]

GSXR 6 speeds have larger diameter gears and the shafts are further apart. In addition they are wider, so the case walls need to be "moved"

I'd be surprised if a 600 Bandit trans could take the HP or torque of a modified GT750.

Allan is correct that you need a set of cases to measure as well as all the parts.

[Suzsmokeyallan]

I don't know which 600 boxes you looked at, but none I have seen have a first gear as large as the GT750/ GS750 and if they have one as large or even larger it simply wont fit in the GT cases.
The Bandit 600 and the GS550 ones I've seen both have smaller diameter gears, the Bandit one also has narrower gears than the GS550.
Theres too many variables here to pick through each model, its time to start buying some used gearboxes or if your local wreckers yard has some for examining all the better.
A 600 gearbox should be able to take the forces of a modded GT engine up to at least 100hp and theres one way to find out.
Being the six speed box has the ratios split up into a closer format, the load on each set of gears is partially reduced compared to that of a five speed box, theoretically anyways.

[tz375]

2001 GSXR is slightly larger and 2006/7 has significantly larger gears. I'd have to check my notes to see which model GSXR 600-750-1000 they came from.

I don't have a set of later crankcases, only the 2001 set.

Dimensions have to be perfect after welding and machining. No place for eccentrics or other adjustable options.

If you can find a smaller model trans that drop straight it, that would be so much simpler than using modern parts. Torque loading on the gears isn't any less with more gears but running the trans faster with a different primary ratio can make a huge difference. Good examples of that are RD250 vs 350 Yamhas and TR750 vs GT7590 Suzuki.

[Suzsmokeyallan]

Richard we need to start comparing notes for the various gearboxes tried so far.
First gear on the output shaft has the largest gear as you know, so it has to have correct case clearance for the GT cases. We already had an issue with making some space in the upper case shield and screw area simply because of the slight difference in the GS first gears diameter, (slightly larger).
I was told a certain year of GSXR 750 six speed transmission will drop right in the Mk1 1200 Bandit cases to replace the five speed unit but I have yet to get around to locating one thats complete with all of its parts. This alteration will be able to take the load as the GSXR750 delivers more power than a stock or slightly modded Bandit 1200.
That gear box design has some large diameter narrow gears in it with closer spaced teeth, and so the shaft centres for those years of bike are very close together. Because of this design those gearbox types wont work in the GT cases.

I've noticed nearly all of the Suzuki gearboxes from the early 90s and later have larger diameter gears with closer spaced teeth, that are also thinner than the earlier years. Those earlier designed gears are usually a bit smaller in diameter with wider spaced teeth and the gears are also noticably wider.
We need to be looking at Suzuki gearboxes made before 1993 as those tend to have the shafts further apart like the GT 750 when compared to the later ones.
Some searching of the available Suzuki bikes with six speed gearboxes is needed, then narrow them down to those of 550 cc or higher, then looking at shaft centre distances next.
Another issue is fork shafts, some six speeds have two fork shafts while others have one. The
GT uses two shafts.
I believe the internal casting on the GT engine may end up having an alteration that allows moving the shift drum, fork shafts and selector mechanism around a bit from their present locations.
Thats a time consuming thing to deal with because it involves a lot of re-engineering.
The GS550 gear box I have is a tad too wide which is easier to fix than moving the bearing locations, but to add to what I just said, the gear shaft centres compared to the GT750 were also not correct either.

Then theres Kawasaki, the closest bike to Suzuki in regard to how the parts are designed. What six speed Kawasaki gearbox could be out there that may work as a 'drop in' or near perfect drop in.

[Cyzygy]

I'm told Yamaha R 6 around 2001 has the same shaft spacings as the GT.
Bob

[Suzsmokeyallan]

Thanks for the information, can you get more details from your source as that will be extremely helpful.
This is that particular gearbox, its impossible to say how close it is dimensionally, but the clutch basket spline means you need to use the R6 basket which brings other possible issues. The shift forks look long enough between the shaft and yokes which is very much like the GT

http://www.ebay.com/itm/2000-Yamaha-R6- ... e6&vxp=mtr" onclick="window.open(this.href);return false;

[Suzukidave]

bump to the top

[diamondj]

I have a GS550 six speed box but no selector drum parts, I know its a bit too wide but I can address that issue, its the drum I need to get to check the other major issue for.

Allan,

I just bought a GS550 box to see if it could possibly fit into a T500 crankcase since the GS550 uses a single shift fork shaft like the T500. It has the shifter drum. I could take photos and measurements if that would help you?

Jim

[Suzukidave]

Jim , what was the outcome with the GS550 transmission ?

[diamondj]

Jim , what was the outcome with the GS550 transmission ?

Just for the GS550 bits in the mail a few days ago. Will try to take a look over the weekend.

Jim

[tz375]

Resurrecting an old thread just in time for Halloween.

Does anyone have any idea how much HP can be pushed through a GT or GS transmission before things start to break?

The reason I ask is that I dug out the GS trans and two GSXR transmissions and 2001 and 2007 have very different bearing and oiling arrangements but dogs and gears on 2001 are similar. 2007 has much larger everything (except dogs which are tiny). Gears and bearings are much larger - presumably because power was much higher.

We are planning on getting more HP out of this motor than anyone this side of the pond (aim high, right and don't let facts get in the way of a good story) and it's records we want to break - not bones and bikes.

I guess whatever Brett deStoop uses on his LSR bike is good enough for the rest of us but I have no idea what he uses in that beast. Nothing else is stock so I won't assume the transmission is either.

What about that double engined drag bike? what trans and clutch did it use and how much power was it making? That would be a pretty good gauge of what is needed.

[Suzukidave]

High on the list would have to be straight cut gears off the crank to the clutch .

[water cooled]

I agree w Dave and would add that the clutch basket needs to transmit all that power too The stock basket can't be far from its limit but billet baskets exist and can be fitted to a straight cut gear

[old racer]

I had run my single motor drag bike around 100-110bhp never been on a dyno,for around five seasons,15 t0 20 events per season never ounce had a gearbox problem.
Only run the double motor for a season same spec cylinders as single motor,Never had a gearbox problem,
They seem to be bullet proof.

[tz375]

Thanks guys.

I was already figuring that straight cut gears are a must above a certain level of power. On the BDK site there's a picture of a shattered basket and they say that above 120 HP the clutch ain't goi'n to take it any more.

Nice to hear that the twin triple could deal with all that torque without spinning the pressed on gear or shattering teeth. That gives me a lot more confidence and reduces the amount of work needed to fit the GSX750 trans. Did the double motor have a dry clutch and straight cut primaries or did it run a more or less stock trans? And how did you get past the huge 1-2 shift gap?