Gearbox Identification

[M_Pied_Lourd]

I need some help identifying the gear box that I have in a newly aquired 1960 TR3A.

I climbed under it this morning and recorded this number;

CD 43419

Any help would be appreciated.

Thank You,
M. Pied Lourd

 

[SpitBang]

According to my reference, the CD gearbox prefix was used on the TR5, TR250 and TR6

https://club.triumph.org.uk/prefix1.htm#TR2-6

 

[TR3driver]

I believe that would make it a 4-synchro TR6 box, likely from a late 71 or early 72 TR6.

It's a good choice, I'm running one about that vintage myself. The case is somewhat beefed up; and just slightly longer than the stock TR3A gearbox (perhaps 3/8") but otherwise it bolts up perfectly. Hopefully someone has put a TR3 shift lever on it, as the later levers look odd to my eye in a TR3 (and some of them hit the dash).

 

[Don Elliott]

Heavy Foot - My 1958 TR3A is very original with all the original numbers. I bought it brand new here in Montreal a little over 50 years ago.

My Comm. No. is TS 27489 LO
My Engine No. is TS 27789 E
My Gearbox No. is TS 27764. It does not have synchro in first but I bought the car with the factory-installed overdrive option.

If the gearbox in your TR3A is from a TR 250 or later, it is a good choice as you now have synchro in first. You can't imagine how I feel when I come to a stop sign and REALLY have to come to a full stop before I can engage 1st gear. The idiots behind me assume that I'm going to do a rolling stop like they always do and then step on the gas. But there I am, not yet fully stopped till I make my full stop.

I fear that some day, someone will smash me in the rear end.

 

[Andrew Mace]

Gee, doesn't anyone know how to double-clutch down to a nonsynchro 1st any more?

 

[M_Pied_Lourd]

Thank You for the info.

Randall, it does have the short TR3 shifter installed.

As far as the rest of the car, I believe that it is a TR4 engine. I couldn't read the number as the bracket for the coil seems to be in the way in order for me to get the first couple of numbers. I know that the oil filler cap is towards the bulkhead. When I get the number, I will post back for further info.

As far as the differential is concerned, can the number be found from looking up under the car or is it located on top of the differential and blocked by the body?

Thanks Again,
M. Pied Lourd

 

[Don Elliott]

Andy - I've been through enough lower lay shaft replacements in 50 years of driving my TR3A to know better than try that double de-clutching down into first gear again. It can get really expensive.

As for the differential it doesn't have a serial number. Most have a 3.7 to 1 reduction ratio with 10 teeth on the input drive pinion gear and 37 teeth on the large crown gear.

 

[TR3driver]

While it's always dangerous to disagree with Don, I was under the impression that they were serialized. Unfortunately the number is supposed to be on the top, where it's difficult to see with the axle installed. Here's the diagram from the factory manual, showing where the number is located.

However, the TR4 axle is several inches wider than the TR3, so it would be obvious if someone had swapped it over. Even stock size tires & rims rub on the fenders with the TR4 axle under a TR3 body (though I was able to pull the fenders out enough that they only lightly rubbed and didn't ruin the tires).

Although rare, there were apparently a few of them delivered with 4.10 rear axles (normally available only in combination with overdrive). TS39781LO apparently was so equipped (but had a later 3.70 axle when I got it).

 

[TR3driver]

One other small correction, Don, the 4-synchro box started with TR4 (and late TR3B). But I'll agree about double-clutching into first, I never could get it consistently smooth with the extra-low first gear in the original TR3 box. Instead, I found that 2nd gear worked better for a 'rolling stop'. With the stock camshaft and flywheel, these engines will pull smoothly from well under 500 rpm (about 5 mph), so just let it walk off with all that low end torque.

 

[M_Pied_Lourd]

Don/Randall,


I believe that my car might have the 4.10 (4.11 actually I think)and it does have the A Type overdrive installed. I will have to wait to drop the Diff to find the number however.

Now, on to the next question. There will be quite a few while I try to get this car sorted out!

The question is regarding the rear brake drums. I believe that the stock drums were 9". I think that I may have 10" drums on mine. Was this an option or an upgrade that was available?

Thanks Again,
M. Pied Lourd

 

[Andrew Mace]

It depends on the vintage of your car. Triumph went back and forth several times with TR2 and TR3 rear brake drum sizes; the last and most relevant change was around TS 56377, when they changed from 10" to 9" rear drums.

 

[TR3driver]

As I mentioned before, it's best to start a new thread with new questions, Pied.

Later TR2 through early TR3A were fitted with 10" drums as standard, but AFAIK they were never optional. However, the 10" rear brakes from a late TR3 or early 3A are a bolt-on to later cars, so someone may have changed yours. Or, since the change to 9" happened fairly late in 1959, it's possible your car was made before the change, but registered as a 1960. My "59" was made in late 58, and the "56" was registered as a 57.

The calibration number on the face of the speedo is a clue to the original axle ratio. The 3.70 axle takes a calibration number around 1180 (several variations); while the 4.10 takes a calibration number around 1320.

The TR3 'performance' axle had 10 teeth on the pinion and 41 on the ring gear, making it a true 4.10.

 

[Don Elliott]

Randall - I see where it would be stamped on the top of the differential. It's been 19 years since we dropped the body back onto the chassis and I don't remember. I don't plan to pull the body off for a while (like maybe another 30 to 50 years or so) and I didn't notice a year ago when I had the whole rear axle out the car.

Pied Lourd - It doesn't really matter what the serial number is on your differential. The ratio is what is important, but if you have no trouble with it, whichever it is, don't get involved with "non-problems", just drive it. You'll love it.

If you tell us your Comm. No., we may be able to answer you brake diamet question.

It seems that there was a colour code (with a wipe of green paint) on the rear cover of the diff if the ratio was one or the other. This was probably to identify the ratio when they were all stacked on the shelf at the factory during essembly.

 

[TR3driver]

It seems that there was a colour code (with a wipe of green paint) on the rear cover of the diff if the ratio was one or the other.

But of course a lot can happen in 50 years. Dealers in particular were known to swap parts around, without worrying overmuch about color codes and such.

If the ratio concerns you, the only way to be certain what you have is to actually count turns or teeth. Probably the easiest is to put the gearbox in neutral and one wheel up on a jack stand, so you can see the driveshaft and the other wheel is blocked from turning; then turn the free wheel through 10 complete revolutions while counting turns of the driveshaft. If the driveshaft makes 18.5 revolutions, it's a 3.70 axle; 20.5 revolutions means a 4.10.

If you can't turn the free wheel under these conditions, you may have a limited slip or welded differential.

 

[M_Pied_Lourd]

Don/Randall/Andrew,

The car is currently not running so I don't know if I have issues with the Diff or not. I am just trying to understand what I have in the car currently. The PO offered some info on the car, but much of it he couldn't "recollect". Alot of the sentences started or ended with "I think".....

As far as the brake drum diameter question, the Comm# is 69911LO.

I will do some checks with the rest of the information supplied above.

Thanks,
M. Pied Lourd

 

[Andrew Mace]

69911LO would've had 9" rear brakes originally. Again, that is not to say that rear brakes, or an entire rear axle assembly, wasn't installed from an earlier car some time in the past!

 

[Don Elliott]

At TS 60000 and after, there were many changes in the sheetmetal body design. For your TS No., you should have rounded bottom corners on your doors. The hinges for the trunk (boot) lid and the front bonnet should be sitting on little raised bases formed from the sheetmetal. The seal in the trunk should have well rounded corners. The floor in the back seat area should be like a full-width raised rectangular bench. There are other differences that you would not see unless you dismantled the interior trim, etc.

It may be possible that someone changed the brake assemblies. But maybe someone changed the Comm. No. plate with a different number. Check the sheetmetal differences detailed above and let us know what you found.

 

[M_Pied_Lourd]

Hi Don,

Confirmed...

Rounded bottom corners on doors.
Raised sheet metal bases under the hinges.
Trunk Seal has well rounded corners.
Forgot to look at the floor in the back seat area....

Thank You,
M. Pied Lourd