[Fot] TR6 gearbox rebuild

Tue Nov 16 07:43:43 MST 2021

 Very good write-up Henry!How I long for the days of the blue & white box marked TKC454...

Glen Efinger

-----Original Message-----
From: Greg Blake via Fot <fot at autox.team.net>
To: Bob Kramer <rkramer56 at gmail.com>
Cc: Fot <fot at autox.team.net>; Henry Frye <henry at henryfrye.com>
Sent: Mon, Nov 15, 2021 4:38 pm
Subject: Re: [Fot] TR6 gearbox rebuild

Agreed. Forwarding to FOT so it makes the archives. That way when I ask this question again in 2 years, someone will remind me to search the archives, again. 
Great stuff. 

Sent from my iPhone

On Nov 15, 2021, at 3:22 PM, Bob Kramer <rkramer56 at gmail.com> wrote:

This is one of those emails to save.  Great info, especially the part that makes it sound like my brain still works. I remember now that I bought a 2nd gear on eBay for a later cluster gear because I didn't have a good later one even though I did have the cluster. Pretty sure Marcel has that gearbox, probably sitting and replaced with a dog box.
I have built 3 CR gear boxes and I did a lot of studying each time, and was confused along the way.  The TRF Blue TR6 catalog is a tremendous resource in that area.
I have a Stag Overdrive gearbox sitting and a CR set new in the box for the next time I need one. It has the longer pilot snout and if I recall (here we go again) the clutch shaft is set up for RHD. 

Bob Kramer

On Mon, Nov 15, 2021 at 1:27 PM Henry Frye <henry at henryfrye.com> wrote:

OK, my bad. I replied without looking at the diagram, and just like Bob, relying on the memory these days is sketchy at best! The close ratio gearset consists of 4 pieces, the new input shaft, which is 4th gear, and the corresponding layshaft gear, plus the two gears that make third. Since the input shaft set drives the layshaft, and it is a different ratio from stock, that's why the first and second gear ratios change. That funky steel bush that is shown is needed so the set will run with either of the mainshafts, you might need it, you might not depending on what size the end of the mainshaft is. 
To build the ultimate box, you DO want to start with gearset from a late TR6, because that will get you a TKC454, the second gear that uses the steel top hat bush. We like the TKC454 instead of the one that used the bronze top hat bush that bronze bush always breaks! However, the replacement bush you get these days for second gear on the mainshaft is a steel two-piece affair, and I have built several boxes with that steel bush assembly with good results. I would put that into a race box without hesitation if I could not get my hands on a TKC454.
Like 15 - 20 years ago I could find an NOS TKC454 every now and again, and somebody even made them for a while, but I never thought those repro gears were all that much to write home about. I don't think the snycros grabbed the cone all that well.
As far as what you get, forth gear is 1:1, just like stock, so your top end calculations do not change. C/r second gear is pretty close to stock third gear, and c/r third is an even split between c/r second and top. We really don't care all that much about the first gear ratio, it's a paddock only gear. What many guys have found is if you run a 4:10 rear and have a billet bottom end and have a cam that will make power to 7K, you do not need an overdrive for the tracks we run. If you run one of those tracks like the old TWS where you actually get to maximum velocity and just run at that speed, well, you might need an overdrive! I used OD in my TR250 because I do not run a billet crank in that car, and shift at 6000. That setup has worked VERY well for me, the car has taken a handful of firsts, and countless second place finishes. You want the 22% overdrive from an early car, not the 25 or 28%, you will find you are losing too many revs to be able to accelerate! 
The c/r gearset works great in a Stag case, the reason they are saying not suitable for Stag (and Sprint) is the input shaft length is different. The Stag case has the same bellhousing specs, it's just the inside of the gear case that is machined differently to accept the improved layshaft design, the roller bearings replacing thrust washers and 3 bearing on the countershaft instead of 2. Yeah, I know the new trick thing to do is to bore out the old layshafts for to accept the third countershaft bearing, that's all well and good, but the layshaft will still be banging on thrust washers instead of roller bearings! 
The 1X23 spline is a standard item, if you are running a Tilton or Quartermaster they will be able to supply your friction disks with that spline. I run stock TR4A-6 pressure plates, so I get my clutches made at California Clutch. Simply order whatever the diameter is (sorry, no notes handy), and tell him the 1X23 spline, whether or not you want springs (I never get springs, just the solid disc) and what friction material. I go 6 paddles, full metallic. Every couple seasons you put a new pressure plate on, it's a wear item. The setup will take a little sliding with no ill effects, just keep all clutch sliding to a minimum and you will be fine.
I always reuse good OEM syncros on my race boxes, if the donor box has OEM syncros I keep them matched up so they go back on the same gear. Obviously, they need to measure a good, sloppy 30 thou to be good. I am waiting to see of Rick Parent makes these new 21st century syncros for the big TR boxes, that could be a game changer!
Probably way more that you were asking for, but I was on a roll. Hope this helps!
Henry FryeTriumph Technology Consultants860.508.3118 - mobile
From: Greg Blake <gblake58tr3 at icloud.com>
Sent: Monday, November 15, 2021 10:30 AM
To: Henry Frye <henry at henryfrye.com>
Cc: Bob Kramer <rkramer56 at gmail.com>
Subject: Re: [Fot] TR6 gearbox rebuild Henry,
Do you get a new 2 gear pair with the close ratio set?  I thought you got a new input gear, 3rd gear pair, and 4th gear pair. 
That’s what I read in the Moss Europe catalog, not saying that is accurate though. I’ve always been curious as to what all the close ratio set includes and the different gear ratios it produces. 
Here is a screen shot from the Moss description. 

Sent from my iPhone

On Nov 15, 2021, at 8:42 AM, Henry Frye <henry at henryfrye.com> wrote:

I am not sure what starting with late TR6 box gets you if you are going to use a close ratio gearset. The big difference is the improved second gear, TKC454 if memory serves, but you get a new second gear with the close ratio kit. You want to convert all the bushes on the mainshaft to steel, so that is easy and cheap.
I believe the ultimate TR race gearbox gets built off a Stag core with its layshaft bearings vs thrust washers. The close ratio kit drops right in, with the correct mainshaft you can run either an A-type or J-type OD. I ran my TR250 racer with an A-type for several seasons, it took an amazing amount of abuse and the OD has never needed a thing. 
Per JK, all clearances set at the bottom of the range so the gears have minimal wiggle room on the mainshaft.
I run Brad Penn 80w90 gear oil, after every race weekend I pull the gearbox drainplug and let a cup or so drain. I inspect and clean the magnetic drain plug, replace the plug, then remove the big OD drain plug to check the screen for debris. Reinstall letting as little fluid drain as possible. The top the oil back up, usually a bit more than half a quart. This keeps an eye on the condition of the internal bits, if you find anything scary address it now!
That's about it, but I must admit I put a T5 in the 250 this spring. Not sold on it lowering lap times, but it sure shifts fast! The TR3 still runs a Stag box, close ratio gears without OD. 
Henry FryeSent from phoneFrom: Bob Kramer <rkramer56 at gmail.com>
Sent: Monday, November 15, 2021 7:41:19 AM
To: Henry Frye <henry at henryfrye.com>
Cc: Greg Blake <gblake58tr3 at icloud.com>
Subject: Re: [Fot] TR6 gearbox rebuild Henry 
Thanks for the additional info. My memory never was that great!   Greg, I didn't realize that you were still running stock gears in the TR3.  The endurance TR6 has the close ratio set.  It is easiest to start with a 73 or later TR6 box.  
Bob Kramer

On Mon, Nov 15, 2021 at 5:27 AM Henry Frye <henry at henryfrye.com> wrote:

Hey Bob,

I believe JK's magic box was with an OD, and gave you proper gearsplits between 2, 2OD, 3, 3OD and 4. I was not aware that he came up with anything that didn't use the OD, because that is what we use the close ratio gearset for!

Greg, are you still using stock TR gearsets, not the close ratio gearset? The close ratio is what everybody up here races with, Ken Gillanders used to say that one change is worth a couple seconds at any track. He was right. It eliminates the huge RPM drop between 3 and 4.

https://rimmerbros.com/Item--i-GRID600088

Henry Frye
Triumph Technology Consultants
860.508.3118 (c)

-----Original Message-----
From: Fot <fot-bounces at autox.team.net> On Behalf Of Bob Kramer via Fot
Sent: Sunday, November 14, 2021 8:24 PM
To: Greg Blake <gblake58tr3 at icloud.com>
Cc: Fot <fot at autox.team.net>
Subject: Re: [Fot] TR6 gearbox rebuild

JK Jackson had that all figured out for a non overdrive box with the goal to get a better 2-3 spread.

Sent from my iPhone

> On Nov 14, 2021, at 6:36 PM, Greg Blake via Fot <fot at autox.team.net> wrote:
> 
> I’ve been inspecting the gears I took out of my race car. Second gear appears to have the slightest blue tinge to its color now. Is there a way to check if there is some damage caused by over heating?  Everything seems good from a tolerance perspective, just concerned about the slight blue color. 
> 
> Related note. Is there a combination of gears I can use out of different gearboxes to give a better split between 3, 3OD, and 4th?  Right now I just skip 3OD because it is very close to 4th. I have a ton of gearboxes laying around, so if there is a combination I should try I’d love to give it a shot. 
> 
> Sent from my iPhone
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