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Discussion Starter #1
The manual calls for 90 wt gear oil for the tranny on my '78 T140v, but even after adjusting the clutch, the gearbox has gotten rather clunky. I was thinking of running straight 50 wt oil in her to see if that'll make shifting any smoother.
Does anyone have any thoughts yeah or nay?
 

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I have lots of thoughts which I will keep to myself.

Just I question have you found a 50wt oil that conforms to GL4/5 specs as in Hypoid gear oil?
 

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Don't use engine oil in trannys and vice versa. If your're having a lot of trouble shifting, maybe check and find out why. Otherwise you could try synthetic gear oil.
 

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Discussion Starter #4
I have lots of thoughts which I will keep to myself.

Just I question have you found a 50wt oil that conforms to GL4/5 specs as in Hypoid gear oil?

KADUTZ, I've read some of your stuff on here, and I value your opinion. So if you will, please share your thoughts.

And no, I don't know anything about GL4/5 specs.
 

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Discussion Starter #5
Thirdbike - Thanks; I value your opinion too. Maybe I was looking for a quick, easy fix for my tranny troubles - summer is way too short up here. I'll dig into the gearbox a little.

But why not put engine oil into the box? Are the stresses just too great? I had a Ford Ranger that called for ATF(!) in the manual transmission. And my Suzuki shares its 10-40 between the engine and gearbox.
 

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Factory Triumph workshop manuals call for 50w engine oil in the trans. I run 50w in my 1970 T120 and it shifts great. My Brit sports cars call for 30w in the gearbox. I had 90w in there and once I realized they called for 30w I switched. Much better. I think either one will work fine.
 

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gabsdad8
Listen to thirdbike

you no want me to share my thoughts I would only get banned again.

you have a 1 owner 78 what does you owners manual call for? I use 85/140 Hypoid gear lube with an additive (made by Lubeguard) in my 78. Pat Owens 400,000 mile RT uses a mixture of gear lube and STP. Older Brit bikes may have used 50wt but then they changed to Hypoid and used that til the end. GL4/5 is a rating applied to Hypiod oils like SJ or SH to engine oils. I can see no advantage by reverting to 50wt
jus my pinion
K
 

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aceacea
my old friend good to see you out here granted the earlier manuals may have called for 50wt the later bikes(T140) called for 90 or 90/140wt Hypoid. (By the way I use the same mix in my RT as the T140's.)
By the way what do you use in the Nortons gearbox?
just the K's pinion
 

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K, I am doing well. We have had lovely cool summer weather here so run my bikes as often as I can. I must still admit the Norton is still my best friend to ride. I have tried to warm up to the Triumph but it just does not have the comfort or the grunt of the old Norton. You should get one! I run 80-90 in the Norton trans. You can tell it is more slugish until warmed up. If I were abusing the thing I would use 80/90 in the Triumph. I may try it just for comparison purposes. My riding is limited to about an hour of virtually non stop cruising on lovely back country twisties. I hate traffic and the clutch on the Triumph is very stiff versus the Norton. I don't think it makes a dam what lube you use as long as it is maintained and changed once in a while. P.S. I have pictures of my brother flushing his primary after adding some STP to it back in 1970. I had a good laugh. Some STP in the trans might be a good idea. I have many cans of it kicking around. Keep well and ride on.
 

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Discussion Starter #13
Thanks again to everyone who responded to my question. After some consideration, I've decided to take a look inside the gearbox to find the cause of the rough shifting.

Even after being together 31 years, there's always more to learn about her.
 

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I don't know much about oil but posed similar questions when starting my 79 bonnie rebuild on this site
http://www.classicbikeforum.co.uk/

The problem can be not what is written in a 30-40 year old manual, but what's the best obtainable oil now. Triumph looked at what was the best then.


My old Tiger Cub never ran well without frothing when using multigrade so I use 30W. I run the Bonnie on 20/50. But oil has come on and there may be a better substance. I use silicone brake fluid not because it is "better" but because it doesn't go off.
 

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I agree with KADUTZ.

Use 85/140 Hypoid if you want longevity.

If you want quick shifting or live in a cold place, go with Hypoid 90 wt.

Motor oil doesn't provide a cushion and the gears will not last as long as nice heavy Hypoid.

My 2 cents.
 
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