Mmmm ? sounds like an excuse to swap the two engines to see which car ends up
with the vibration!
Duncan Charlton
1121 Lower Elgin Rd
Elgin, Texas 78621
USA
> On Jun 9, 2017, at 1:00 PM, Brian Schirano via Fot <fot at autox.team.net>
> wrote:
>
> echoed problem here w/my GT... still
>
> motor was completely balanced, alum flywheel balanced and the pressure plate
> balanced indexed to the flywheel, decent damper. Driveshaft re balanced and
> phase corrected like Scott. I run different axle so only have inboard u
> joints, no phasing there. rebuilt the diff last year, bearings good, still
> have rubber mounts, but newer, and the pressed rubber mounts in the diff new
> neo. I will have to study driveline angles, I've read about this but have not
> addressed as such. I remember it's counter intuitive, they should not be
> completely straight.
> This year when I finally get to my only event, VRG at the Glen, I will be
> running last years tires on TR7 steels vs my old alloy BWAs and see if that
> makes a difference. My buddy that mounts and balances took extra care and saw
> no runout or flat spots.
>
> Interesting, we also run a TR6 w/completely stock motor, and do not have any
> vibration there. Given the care of the GT motor build and none in the TR and
> it's longer stroke, make me wonder. (although the GT does run sometimes up to
> 1000 more RPM on periodic long passing straight occasion
>
> welcome more commentary here
>
> Thx
> Brian
>
> 26A GT6+, 28 TR6
> Brian Schirano
> 585-305-0349 Cell
> BSchirano at yahoo.com
>
>
> From: Scott Janzen via Fot <fot at autox.team.net>
> To: kkjjk at aol.com
> Cc: 'Friends of Triumph' Triumph <fot at autox.team.net>
> Sent: Friday, June 9, 2017 10:58 AM
> Subject: Re: [Fot] vibration
>
> I used to have the exact same problem with my GT6, also noted in the same
> spot at Summit Point. I?m still not convinced it is not related to RPM - in
> lower gears, you run through this range much more quickly, and I think it?s
> the RPM combined with the speed and the longer time you spend in this RPM
> range.
>
> Anyway, I found that both my driveshaft u-joints were slightly out of phase,
> as were the u-joints on the rear axle half-shafts. I don?t know what your
> half-shafts are made with - cv joints, u-joints? Mine are Spicer splined
> sliding half-shafts with inner and outer u-joints. A good driveshaft shop
> corrected both of these issues, balanced everything, made sure all the
> u-joints fit tightly in the yokes, etc.
>
> The other thing I spent some time with was the alignment and mounting of the
> differential. The GT6 has far from optimum alignment of the differential
> relative to the transmission - poke around on this subject but here?s one
> article http://www.markwilliams.com/driveshafttech.aspx
> <http://www.markwilliams.com/driveshafttech.aspx>
>
> Anyway, the best I could achieve was to get the nose of the differential as
> high as possible and the rear as low as possible, if I remember correctly.
> Also, look at the mounts themselves - are they in good shape, tight? My diff
> is mounted with all aluminum spacers front and rear, no rubber, and i had the
> rear ones made eccentrically so that I could adjust the rear up and down a
> bit.
>
> It seemed that a combination of these things worked. No one item was the
> silver bullet. Not sure if this is a new problem for the car - if it is, I?d
> suspect the diff mounts or poor balancing of one of the rotating components.
>
> Of course, we are assuming this is not suspension or engine vibration related
> - good to eliminate all of those as well, but also relatively easy to check
> at speed and you can usually feel it if it?s out at a wheel.
>
> Scott
>
>
> I have a significant vibration with my GT6 which occurs only at speed, in
> 4th gear starting about 300-400 before redline (approx 6600 RPM). In any
> other gear to redline there is no problem, so it is related only to speed. I
> had the driveshaft universal joints replaced and balanced with no change in
> the vibration. The tires are brand new and balanced as well, although I did
> have a bit of shaking of the car, so I will have them re balanced again. But
> I need to know what I should look at next to find the solution to the
> problem. The diff? Rear axles? And what items specifically? I have to back
> off a bit near the end of the straight at Summit Point due to this problem,
> which sucks. A longer straight at another track would be even worse! Any
> help would be appreciated! Thanks- Jay De Pol
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