I certainly never got to the level of Jack and haven't played with these
cars as much as Glen, but during my brief racing career, I too
experimented a lot with gearing. I tried most of the combinations Jack
mentioned. My favorite was almost the same - close ratio TR box with
overdrive and a 4.55 rear. My choice was partly because my home track,
Hallett, is tight, well suited to a 4.55. I had the OD for longer
straights. We (my son Tom and I) ended up using the OD a lot more than
just the straights. Like someone else said, sometimes you're too busy or
it is faster or more convenient to shift the overdrive. I always like to
tell the story about the time a throw out bearing went bad and I
couldn't shift the tranny, so I ran Hallett using just 3rd and 3rd-OD. I
was off my best lap? by only about 1 second. However, there was one
other time when we lost overdrive and had to limit our speed on the long
straights.
A final word I will say. I think a lot of people shy away from an
overdrive because of "fear of the unknown". In reality they are simpler
than the transmission. Some people want to just buy a unit and bolt it
on. Regardless of the route you go, I think you're in for a rebuild.
I've never rebuilt a 5 speed, but I've done 3 speeds and 4 speeds. If I
extrapolate the differences in complexity, I really don't want to
rebuild a 5-speed.
?- Larry
On 7/19/2018 4:57 PM, Jack Wheeler via Fot wrote:
> Hi Glen.? I agree with most of your comments.? I raced a TR-4 in SCCA
> for 24 years, and used both close ratio, and stock ratio gearboxes
> with, and without overdrive.? I always used the later housings (TR-4A
> - TR-6) and the "A" Type overdrive, and I did all my own maintenance.?
> Early in my career, I always thought a straight 4 speed (without
> overdrive) would be more efficient for racing, due to less parasitic
> losses.? When close ratio gears became legal (about 1980), I thought
> this would be a big improvement over the overdrive option.? I had all
> 6 gear sets set up for my IRS car, so I could gear to use either
> transmission option at all the tracks I raced at.
>
> However, after years of experimenting at Road Atlanta, during The
> Runoffs, I concluded that using a close ratio overdrive gearbox with
> the 4.3 rear end gear was about 1 second per lap faster than using a
> straight 4 speed with the 3.7 rear end gear.? The 4.3 rear gear gave
> me a more usable second gear for some tight turns (like turn 7 at
> Atlanta) than the 3.7 rear gear.? I also tried the 4.1 rear gear with
> the straight 4 Speed, but the overdrive option was still faster.
>
> I did less research at other tracks, but long tracks with tight turns
> (like Road America) would certainly favor the overdrive option.? There
> may not be as much difference on short, tighter tracks.? But, numbers
> don't lie, and a second a lap was worth it to me, to learn about
> building and maintaining overdrives, with high pump pressure for
> quicker shifting.? And, I found them to be very reliable
> mechanically.? The only problems I ever had were electrical.
>
> Take it for what it's worth, but that's my story, and I'm stickin' to it!
>
> Jack
>
> On Thursday, July 19, 2018, 5:30:21 PM EDT, fubog1 via Fot
> <fot at autox.team.net> wrote:
>
>
> In all fairness to the conversion advocates, in spite of the benefit
> of both intermediate gearing & the extra top gear with the O/D unit,
> there are some downsides to the O/D.
> First, it's getting hard to find good units, a lot of what I run into
> is junk. These have been in high demand since forever, I've bought
> many junk TRs just for the overdrives.
> As Larry pointed out, there are alternatives, ie Volvo, but then you
> have to mod it to suit.
> Unless you find a guaranteed plug-and-play TR box & O/D assembly,
> you'll most likely be having to go through the gearbox as well, and
> certainly if you're converting a standard gearbox to overdrive cuz'
> the mainshaft is different.
> That leads to another problem, parts availability for overdrive parts
> is a bit limited, especially some of the early A-type stuff, and as is
> normal these days, quality is always a big concern.
> Then if you have a rebuildable unit, and all of the parts, it has to
> be properly rebuilt, by the book.
> It's a fairly labor-intensive job and requires some degree of
> mechanical finesse.
>
> If you have to pay someone to do the entire job, the cost could easily
> get up there to the point where a conversion gets more attractive.
>
> There are also a few other negatives, the TR box & O/D unit may weigh
> more than some alternative units, there is some very slight power loss
> with the O/D, and some replacements may have better ratios available.
>
> Having said (typed) this, for a street car, a later TR-6 box, with the
> 17 tooth laygear, better 1st ratio & much-improved 2nd mainshaft gear,
> with a J-type on the back of it is hard to improve on.
> For racing, late 6 box with a set of close ratio gears & a "big
> piston" A-type works well.
>
> I see both side of the argument but personally I like the TRs as TRs,
> iff'n in doesn't say Stanpart on it, I'm not interested (grin).
>
> Glen
>
> -----Original Message-----
> From: Larry Young via Fot <fot at autox.team.net>
> To: fot <fot at autox.team.net>
> Sent: Thu, Jul 19, 2018 12:32 pm
> Subject: Re: [Fot] best gearbox for TR6
>
> Yeah, Glen is right. I should have shut up. I did a cost comparison a
> few years ago. Someone was making a Ford 5 speed conversion also. The
> cost was more or less the same, but of course, it depends on how much
> you are going to do yourself. I have heard the Toyota boxes are
> getting scarce also ($550 seems like a lot). Quantum Mechanics does
> (or did) a turnkey A or J type overdrive. He has everything you need
> to convert a Volvo J-type to any of the TR series. I've helped a
> couple of guys do this conversion. Volvo's from the 80's are
> relatively unloved, so a couple years ago I could find the Volvo
> J-types on Ebay for $150. Of course, buying the Volvo overdrive or a
> Toyota 5 speed is just the tip of the iceberg. If you want a turnkey
> deal that you install, you're probably looking at $2500 - $3000
> regardless of the route you go. If you do everything yourself, you can
> probably get by for half that.
>
> I've had my TR250 from new and didn't have an overdrive until 5 years
> ago. I did a 7,000 mile road trip in it a couple of years ago and
> found all 7 speeds to be useful. Even 2nd OD was nice when stuck
> behind an RV going up a mountain pass.
>
> Like I said, I should have kept quiet, but my point is that I think
> you will find the cost similar regardless of the direction you go. It
> really boils down to what you prefer.
> ?- Larry
>
> On 7/19/2018 7:43 AM, Bill Tobin via Fot wrote:
>
> I dunno larry, I got my conversion from Eaglegate, who was also
> from New Mexico, and it bolted in. Plug and play. Works great,
> shifts smoothly, and? (so far!) reliable.
> Me being me, at the time, '13 I think, I picked up two spare
> transmissions. Celica W58. For about $175 each. A friend with a
> wrecking yard looked them? up yesterday: around $550. No, they are
> not for sale!
> I believe a guy in Kansas City took over Eaglegate. If anyone is
> interested, I could look it up.
> Cheers, Bill
>
> On 7/18/2018 11:56 PM, Larry Young via Fot wrote:
>
> I'd rather have an A-type (or even a J) overdrive - 7 gears,
> easier to shift, easier to install, probably less expensive -
> What's not to like? Keep the wife definitely.
> ?- Larry
>
> On 7/14/2018 4:13 PM, dustin nicholson via Fot wrote:
>
> Is the HVDA conversion kit for the Toyota 5 speed still
> available since Herman?s passing?
>
> Dusty
>
> Sent from my iPhone
>
> On Jul 12, 2018, at 8:05 PM, Bobby Whitehead via Fot
>
> My wife is trying to convince me to keep our 1971 TR6
> we've owned for 26 years...mhhhh.... I told her if we
> did I needed an overdrive or 5th gear...what's the
> best conversion?
>
> Bobby Whitehead
> Jester's Racing
>
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