GT750 Howl/Whine in 4th and 5th Gears

[Striker1423]

One of the last rides I took my bike on this late summer I whipped down the freeway for about 15 miles, then got off and was cruising about 50-60 mph. I noticed the bike was making a loud howling noise that changed with the speed of the bike. However, at stop lights the engine sounded fine, no noises. So, has to be gearbox. Bike goes down the road fine. No weird chattering or anything feeling amiss.

I mean the howling was loud over the wind noise, etc. It didn't appear to be there in 1st-3rd. Only 4th and 5th. Anyone have an experience with Suzuki gearboxes sounding so loud (M in SC, Teazer)?   

[m in sc]

yup. my t500 sounds like an old schoolbus in 5th gear. they say its the hardening of the gear has an issue, but ive seen varying reports of how bad it really is. does it make me nervous? sometimes. but its been that way for 6 years . def not good. I'll adress it next time i split the crank cases.

[teazer]

usually it's the second gear dogs that go, but I have a trans here missing al the teeth on 5th gear which is close to what you have there.

You have a few options:
- Buy a used trans off ebay etc and hope it's better than the one you have
- send me the two shafts and hope I can spare a pair of 5th gears to repair what you have- or
- Buy a complete transmission from a 78/79 8 valve GS750 and modify the output shaft and fit all GS750 gears
- Use second, 3rd and 5th gears on both shafts from the GS transmission and keep stock GT first gear.  4th gear did not change in terms of numbers of teeth across all years of GT and GS
- Or get a later 16 valve GS750 transmission and use the gears from that set with updated dog design and slip them onto a modified 8 valve GS750 shaft 
- Buy replacement gears from Nova Transmissions in the UK.

If yours is M or later the gear ratios changed so you have to make sure you get suitable gears.

BTW, a GT550 has many of the same gears as a GT750.  Shafts are different and so is second gear, driven, but that's another source of gears.

[Striker1423]

I saw Nova had full transmission sets as well, but holy chit $2300 for a whole trans is a lot. Looks like an engine teardown is in the works... 

[Striker1423]

Well, did my first cold-weather fire up and its leaking coolant again from the front center large head bolt. Sum bitch. 

[car91r]

Had the same problems with my T500 only it was 3rd and 4th gear. Split the cases and noticed pitting on the offending gears. Picked up another complete transmission set on Ebay. No pitting on any of the gears. Swapped and noise gone. Lately had the same problem with 6th gear on a Suzuki 650 V Strom. Common issue on that bike I found out later.  Must be a problem with gear manufacturing at Suzuki.

[teazer]

A full Nova transmission would be the perfect answer, but lottery winners only for that.  Even 4 individual gears are not cheap. A GS/GSX/GT hybrid might be best but whining is not all that common compared to jumping out of gear with work and rounded off engagement dogs.

When you have the motor out and stripped down, give me a call and let's work out your options.

[Hawaii-Mike]

Interesting and convenient that GS750 transmissions can fit the GT750.