Grinding into 3rd Gear...

[kinggeorge13]

My 1977 Westie I picked up last year came with a rebuilt earlier dual-carburated engine.   I have the receipts where the engine was replaced by a shop several years ago with this dual-carburated older version (then a year later they have a receipt where they bought new carbs as well and replaced them). 

Since the day I bought it, 9/10 times I shift into 3rd, it grinds it's way in (and yes, I realise the longer I do this, the worse damage will get so I'm not driving it hardly at all).   Super-rare times if the engine is just the right speed, it seems to go into 3rd without much grinding but for the life of me, I can never duplicate that success on demand.   And when going higher speeds an using 4th gear there is no way I can shift down into 3rd again.   It does not grind when I'm downshifting, it simply won't let me move the stickshift into the 3rd position.   I end up slowing enough to shift down into 2nd and work my way back up to 3rd from there.  No other gears grind or have issues at all. 

Any thoughts or is this transmission pretty much toasted?   I've never had a transmission problem before this and while I've done lots of other work and mechanical work on my buses, the transmission is a mystical, strange creature to me which I'm only now starting to read up on and learn. 

Thanks!
George and Cosmos (my 77 bus)

[kinggeorge13]

So I've been reading up lots on this.  It seems unlikely that it would help but I have read posts from folks who had pretty much the same or similar symptoms of my bus and say that replacing the transmission fluid with new, high quality transmission fluid (likely synthetic if I can find it in GL-4) and 85W-90.  Otherwise it seems that GL5 can be used but only if it has an MT-1 specification or says it is GL4-compatible.    We'll see how that goes.   I'll do a little more research before picking the best fluid to be used. 

The other thing that has been suggested is doing the adjustment procedure on the clutch.   Again, maybe not too likely but some people profess it fixed their "one gear grinding" problems.   

I'll try both of these before I go the route of finding a transmission repair place that knows these transmissions.   

-George

[owdlvr]

For fluid, I'd recommend Motul Gear300. Though I can't say anything about its ability to assist your 3rd gear syncro, I can confidently say it helped with the same brass syncros in my old Audi rally car transmission. Motul Dealer Finder: https://www.motul.com/ca/en-us/resellers?q=vancouver&activities%5B1%5D=1

Otherwise, for a GL-4 specific oil use Redline MT-90: http://driversedgeautosport.com/redline_MT90.html, available at Lordco or Driver's Edge Autosport.

Don't use Amsoil...though I'm sure someone will post up about how you should only use it. But transmission fluids are like politics, everyone thinks they're right...

[pittwagen]

So have you ever changed the trans oil?  If not, do it and report back as to what your found by way of filings etc. in the oil and anything attached to the magnet on the drain plug.  Any idea how many kms on the beast?

[Bruce]

.....

[Bruce]

So I've been reading up lots on this. 

The problem with taking the advice of the armchair experts is that 99.99% of them have never been inside a gearbox to see the effects of what they condemn or what they crow about.
The Bus guys swear you must use GL-4 oil because that's what their 40 year old manual says.  Of course it says that, GL-5 didn't exist then.  Then they say if you use GL-5, it will instantly eat your synchros.

On the other hand, what makes an oil meet GL-5's standards is the extreme pressure rating.  In other words, how well it prevents metal to metal contact under high loads.  The pressure rating of GL-5 is higher than that of GL-4

When I go inside a gearbox, if I see all the synchros gone, blame it on GL-5.  If the gears are all worn out, blame it on GL-4's inferior extreme pressure rating.  What do you think I see in almost every gearbox, and what has never been seen by anyone?
I see plenty of metal to metal wear, while I've never seen the so-called corroded synchros.

Here's some specific info for your 77 Bus.  If you were parting out a Bus like yours and you wanted to sell your core gearbox, it is currently worth $800C as a core in California due to the high demand by the off road guys.  But before you get that loot, the trans shop will pull off your bell housing to check the R&P.  That's because the #1 failure in an 091 trans is worn out R&P teeth.  They're worn out because so many guys out there are using gear oil that's not good enough at preventing metal to metal contact.

Still not convinced?  There's a compromise out there.  Many GL-4 rated oils do meet or exceed the pressure rating for a GL-5 oil.  These oils say right on the label, Meets GL-4 and GL-5.  Get that one and save your R&P.

All this talk about oil is moot.  Your 3rd gear synchro is broken.

[kinggeorge13]

I was happy until I read your last sentence.    That's my fear as well as I suspect you are correct but it's (almost) free for me to change the transmission fluid and play with the clutch adjustments and if that takes me to where we expect me to end up with a still-grinding into 3rd gear,  I'll have to find someone who can fix it.......wildly assuming that is fixable with parts available.....

To answer a couple other questions from other posters, I don't have any knowledge of anyone changing the transmission fluid previously.   The guy I bought it from only had it a year or two and there were a stack of old receipts in there (replaced engine with a rebuilt engine, then replacing both carbs, etc), there was nothing I saw quickly about changing the transmission fluid.   The owner back around 2000 did do a ton of service with it and lots of oil changes, tuneups and a dizzying amount of parts replaced but it would not surprise me that nothing done with the transmission fluid since then....   The mileage is completely unknown except that the engine replacement happened around 1997.   

Thanks everyone!

-George

[owdlvr]

Oh there is no doubt your third gear syncro is bad. Even the best fluid out there won't fix it, but it might make it liveable.

[jim martin]

Switched from LAT gear oil to this last  3 and 4 gear change.
I was never happy with the way the box shifted hot or cold.
Smooth shifting under full load , excellent product
http://www.torcousa.com/technology/RTF.pdf

[kinggeorge13]

For fluid, I'd recommend Motul Gear300. Though I can't say anything about its ability to assist your 3rd gear syncro, I can confidently say it helped with the same brass syncros in my old Audi rally car transmission. Motul Dealer Finder: https://www.motul.com/ca/en-us/resellers?q=vancouver&activities%5B1%5D=1

Otherwise, for a GL-4 specific oil use Redline MT-90: http://driversedgeautosport.com/redline_MT90.html, available at Lordco or Driver's Edge Autosport.

Don't use Amsoil...though I'm sure someone will post up about how you should only use it. But transmission fluids are like politics, everyone thinks they're right...

from George:  I was looking at the Redline MT-90 75W90 GL-4 over at Mopac in Langley yesterday as I wanted to do my tranny oil change today but I see that it says on the site "Not for use in differentials with hypoid gears"   Doesn't that mean I cannot use it in my 1970s (1974-1979 are what I have) bus transmissions?

Thanks,
-George

[Bruce]

All Bay window Buses and Vanagons have hypoid gears, so do not use that oil.

A hypoid R&P means that the pinion gear is below the centerline of the ring gear.  Manufacturers do this for several reasons.  It allows for more ground clearance (or lowers the drivetrain).  It makes for a stronger R&P.  But the trade-off is that the contact pressures are greater.  The auto makers found that GL-4 rated gear oil did not have a high enough extreme pressure rating to cope with these higher stresses, so the API came out with GL-5 and a higher extreme pressure rating. This is why you MUST use an oil rated GL-5.