75w140 gearbox oil

Technical Big Block Tonti and Loop Frame models
1

I’ve read a couple of blogs in which long-term guzzi owners swear by the aforesaid 75w-140 gearbox oil for improving the feel of the Guzzi gearchange etc. So checking out the options on the Opie Oils website I find 3 apparently different versions of the Redline 75w140 gearbox oil, which to choose? or should i avoid 75w-140?
http://www.opieoils.co.uk/c-674-75w-140-gear-oils.aspx

All 3 versions are synthetic the choices are 75w-140 GL5, 75w-140 NS, both with yellow label, and 75w-140 Heavy Shockproof with red label.

(the bike is a 1986 le mans with around 28k miles, currently with the usual 80/90 gear oil changed about 500 miles ago)

Anyone any thoughts or experience of using 75w-140 in the gearbox?

2

I did, thought it made the gear change smoother and lighter (aka easier). Pretty sure it was by Comma, and 85W-140 not 75W-140.

HTH

3

PS: it just so happens, this is also recommended (by my dealer) for final drive of a Ural.

The annoying thing is I disposed of the leftover stuff for the Guzzi, when actually I could have kept it!


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4

Plus 1 for Comma 85w 140.

Used in Gearbox and final drive of my 1000S - Gearbox slicker and final drive runs cooler than with recommended oil (85W 90 as far as I remember)

5

GL4 spec = gear oil
GL5 spec replaces the old Hypoid oil , and should be used in the rear bevel box .

6

So 75w-140 would be a touch thinner and easier flowing for cold starts, when compared with 85w-140?

7

Doubt difference will be noticable.

FYI I always (well nearly always) pull the clutch when starting so the starter motor is not also turning over the gearbox. Do this in the car too. Become a habit.

8

The way that modern gear oils are engineered, cold viscosity is less of an issue than maintaining film coverage when hot. All of these oils have additives that cling to the gear surfaces and perform well under high hydrostatic pressure.

As far as the gearbox is concerned, you can fiddle with oil grades, but I have found that if your box is clunky then re-shimming and sorting out the gear spacing is a better option. Not for the faint hearted, but do-able (cos I did!). Cheaper first fix is to ensure that the clutch and gear linkage are well-maintained, and then to practice alternative shifting techniques. One is when up-shifting and to avoid “brick-in-a bucket” changes is to lightly preload the shift before pulling the clutch. Can be absolutely silent if well-executed.

Read Pete Roper’s excellent article.