Fluid Change Interval - Trans and Diff?

[RJS]

Hi All,

Just curious what you think is a reasonable change interval - based on either time or mileage - for the transmission and differential?

I drive about 1,000 miles per year. I asked a British driveline expert shop and they recommended once per year which seems a bit excessive. I'm thinking every other year.

Cheers,

Bob

 

[tdskip]

Once a year won't hurt anything of course, but 15K or more was factory requirement I believe. I can check Bentley if no one knows off hand.

 

[Geo Hahn]

Considering that Triumph didn't even put a drain plug in the diff (TR4 and beyond) they weren't exactly encouraging frequent changes back there.

I'll be interested in the replies as I tend to use a long interval. Also -- would using synthetics (in the gearbox) extend that interval?

 

[RJS]

My Bentley actually only states to top up these fluids every 6,000 miles. Nothing about change however. After the trans and diff were rebuilt, I ran them for about 6,000 miles before I changed the fluids (I had a drain plug tapped into the diff) for the first time.

I don't think these fluids get contaminated like engine oil does with nasty combustion blow by. But, I think the rationale for annual changes is condensation and water content accumulating in the oil.

Bob

 

[TR3driver]

The factory recommendation varied with which car ... the TR4 manual says to drain & refill the gearbox & diff every 12,000 miles, but the TR4A handbook says only to top them up every 6,000; never drain & refill. I believe the TR250 & TR6 were the same.

The TR3A manual (Practical Hints 6th ed), OTOH, says the diff should be drained & refilled every 6,000; while the gearbox only needs to be done every 12,000. Since these are basically the same units, I believe the difference is due solely to improvements in gear oil during those years.

I use full synthetic GL5 in my diffs, and only change it maybe every 5 years or so, which works out to roughly 50,000 miles for me. So far, I've not seen any indication that isn't often enough. The diff in my TR3A was already well worn (lots of backlash) when it came to me; and didn't seem to get any worse in some 150,000 miles.

 

[PAUL161]

Just to comment, I still have my old Ford Ranger pickup that has an excess of 250,000 miles on it and the oil in the final drive and manual transmission have never been changed. The rear is as quiet as a church mouse and so is the transmission. No one ever changed those oils years ago, 30s, 40s, 50s, 60s, regardless of what the factory recommended, especially the units that took 85/90 weight oil. It was unheard of. My 93 Chevy truck, that I bought new, has 198,000 miles on it and the oil in the rear has never been changed, just checked every 50 to 60,000 miles. This truck pulls trailers back and forth to Tulsa, a 2600 mile round trip 4, 5 times a year, STILL! There's a lot of semi's out there with an excess of 500,000 miles on them that STILL have the original oil in the finals, crazy but true. Oh yeah, I still have my dads old Farmall tractor that's 68 years old. It's never had the oil in the finals changed either. Just thought I'd throw that out there. Everybody has an opinion, some good, some not so good, but, that's what makes life interesting. 40 years maintaining heavy construction equipment taught me that. Do your own thing and enjoy life, it doesn't last that long! JMHO. PJ

 

[hondo402000]

change??? I thought is was fill up to replace what leaked out! haha

 

[vagt6]

That's good to hear, Randall.

The first thing I do when I purchase a new vehicle is to change the fluids. Unless I'm certain that all fluids are brand new or fresh, I change 'em: coolant; engine; gearbox; diff; brakes, everything.

Sometimes, the fluids/lubricants can tell stories if you inspect them closely.

 

[RJS]

Well, now I am leaning back to a 6 yr/ 6,000 mile change interval given the light service my car enjoys. I do enjoy working on my car but, with a family and limited time, I would prefer to spend my time working on car improvements, not unnecessary routine maintenance. Plus, I have been the victim of fixing something that wasn't broken before. Typically, that involves opening up something that was working just fine only to create a can of worms. Sometimes, I can't resist.

As I read once, there are two schools of thought on car repair:
1) fix only what's broken, or
2) everything has be be taken apart, cleaned, checked and replaced to confirm it's in good working order!

This is a bit different since I am talking preventive maintenance v. repair. But, I am sure there is a law of diminishing return here. When I was in high school I worked in a gas station pumping gas. They guy I worked with on Friday eves would throw his Buick Skylark up on the lift and change his oil every Friday night!

Bob
PS: but I will still check the fluid level once a year. Before I had the diff rebuilt it leaked real bad. The person who rebuilt it said I had saved the ring & pinion ($$$) by keeping the gear lube topped up so it never ran dry!