View Full Version : TR4/4A Oil to use? TR4

05-13-2006, 04:41 PM
My manuals haven't come yet... Which oils should I use in the trans (no overdrive) and the rear?


05-13-2006, 05:08 PM
I'd say 20w50 Castrol (what I use in my MGB), but I'll let someone else who knows Triumphs chime in /ubbthreads/images/graemlins/grin.gif

05-13-2006, 05:13 PM
Hi Larry,

Use *GL4* gear oil in both gearbox and diff. No GL5 (has sulfates that will eventually damage brass parts used in Triumphs).

Most likely, you'll find 85w95 at an auto parts store. That's fine. 90w was the original spec.

An alternative, if you can't find gear oil, is 20w50 or straight 50w *racing* motor oil. Don't use a non-racing motor oil, since they have detergents in them you don't want in either the gearbox or the diff. I'd much prefer to use GL4 gear oil in the diff, though. (NOTE: this is for non-OD gearbox as you indicated. If there were an OD, I'd recommend 30 or 40w racing motor oil, the lighter if it was recently rebuilt, the heavier if there were some miles on it.)

Some folks use and like them but I don't recommend any synthetic oils for our old cars. There have been a lot of reports that synthetics cause the TR gearbox to start popping out of gear (often 2nd gear, during deceleration... the problem is usually solved just by switching back to mineral-based oil). In the rear axle assembly, there are seals that might be "encouraged" to leak with synth. In the engine, most synth. have too much detergent, plus the engine was designed long before synth oils were common, with tolerances for mineral-based oils and to run with a bit of carbon around the rings, etc.

Personally, I prefer Valvoline oils, but there are many good brands out there.


05-15-2006, 07:43 PM
Do not use motor oil in your Tr's gearbox or diff. It was designed to use 80-90 wt gear oil. Some car makers (MG etc.)do call for motor oil in the gearbox, but not Triumph. Synthetic oils of the proper wt. will work fine, but if you have leaks with the present oils & old seals they will be worse with synthetics.

05-16-2006, 04:36 AM
Do not use motor oil in your Tr's gearbox or diff. It was designed to use 80-90 wt gear oil.

[/ QUOTE ]

Hello Duane.
John Esposito, the owner of Quantum Mechanics and the guy that built my J-Type overdrive, said he will void my warrantee if I used anything but 30wt Non-detergent motor oil in my tranny/overdrive. It seems that 30wt motor oil and 90wt gear oil have similar properties. Something about how the viscosities are measured at different temperatures.


05-16-2006, 03:17 PM
Hi Bill,

And, I'll take his word for it! Heck, John Esposito has probably taken apart and rebuilt more TR gearboxes and ODs than all of us put together have ever even seen.

Last time I looked he had a detailed explanation on www.quantumechanics.com (https://www.quantumechanics.com) of tests he's run with various oils and why to use 30w non-detergent oil in his freshly rebuilt OD gearboxes. In a nutshell, it has to do with heavier oils (which *were* originally factory-specified... hindsight is 20/20) causing the hydraulically-actuated OD to over-pressurize and stick in the "engaged" position. That could be disastrous if the car is reversed, for example. This seems to be particularly true of the A-type, which runs at a significantly higher internal hydraulic pressure than the J-type, but to some degree effects both types of OD.

Keeping in mind that the OD and a TR gearbox share the same oil - but use it for different purposes - 20w50 motor oil and 80/90w gear oil are simply too heavy. By different purposes I mean that the gearbox uses oil for lubrication and cooling, while the OD uses oil for hydraulic operation, lubrication and cooling.

An OD's accumulator and pump will wear gradually over time and miles, reducing internal hydraulic pressure. So, I think there is a case for using slightly heavier 40w non-detergent motor oil in older, higher mileage OD gearboxes (which are certainly out of any warranty, too, BTW). A key indication when this might be a good idea is if the OD starts to be slower to engage even though it has been adjusted correctly. Heck, there might even come a time when 20w50 or straight 50W motor oils or 90w gear oil can help keep a really high mileage OD unit on the road a little longer before it's rebuilt (hard to tell without running pressure tests, though).

But, it's important to note that this thread initially was dealing with the question of what oil to use in a *non-OD* TR gearbox. While the same lighter oils would probably work fine in them, in non-OD gearboxes there are no hydraulics to worry about so it just makes sense to go ahead and use a heavier oil - either the original spec 90w GL4 or, optionally, 20w50 non-detergent motor oil.

20w50 (or straight 50w for that matter) *non-detergent* racing motor oil is almost exactly the same viscosity as 90w gear oil. The main difference is that gear oil has modifiers added for higher pressure gear meshing. However, the TR gearbox doesn't have the type of gearing that requires these. So, 20w50 is a viable option for non-OD gearboxes, especially since GL4 gear oil can today be a bit hard to find (GL5 is by far the most common in the stores near me, and definitely should not be used because the pressure modifying sulfates in it *will* attack and gradually damage the brass parts in TR gearboxes).

Plus, many people have been using 20w50 non-detergent motor oil in non-OD TR gearboxes over the years. It's well proven.

I do prefer to run an actual gear oil in the diff, where ring and pinion gear mesh pressures can be higher than in the gearbox. I can't recall any brass in the diff to be concerned about, but will stick with GL4 anyway, just to be safe.

With the possible exception of certain Redline gear oils, you'll likely never find synthetics oils in any TR gearbox or diff I ever own (probably not in the crankcase, either). IMHO it's a waste of money and the additional slipperiness will more often than not cause problems popping out gear. I've got a non-OD TR4 gearbox with around 150,000 miles on it, including some track time, that's never even been opened up, let alone rebuilt. It's always had mineral-based oils in it. Works fine except that the 1st gear synchro is a bit baulky. (Sorta like driving a TR3 /ubbthreads/images/graemlins/wink.gif)

Another consideration regarding synthetic oils in OD gearboxes, specifically: The Laycock overdrive has an oil-bathed clutch in it. Older originals or modern replacements of this might or might not be okay with modern synthetic oils, I don't know for certain. However, I have seen oil-bathed clutches in motorcycles ruined almost immediately when synthetic oils were used (note: these were older motorcycles, modern ones might use different clutch friction materials that are okay with synth oils). I have no way of knowing if this was because the oil is slipperier or because in a motorcycle the clutch shares oil with the gearbox *and* crankcase, meaning it's usually a detergent oil. Many synthetic motor oils are really loaded up with detergents (especially the extended mileage types). It could have been the detergents or the extra slipperiness of the oil - or a little of both - that took out the clutch. Either way, it's no fun having to replace a clutch in a motorcycle *or* a Laycock OD, so why take a chance? I'll just stick with non-synthetic oils. They're cheaper anyway, not to mention less likely to leak!