The biggest concern out there, and I have read several on various lists ... is about brass Borg-Warner style synchro rings. Obviously, not a problem with 915, 901, and 356 transaxles!

I suspect the 'problem' only occurs when the gear oil is left in the transmissions for extended intervals beyond what would be advisable or reasonable, though that issue of time has not been raised on the lists or at the petroleum sites. In these days of disposable vehicles, and 'reduced' maintenance, Honda-style, the car mfrs seem to have erred in the realistic needs of gearboxes vs a perception of reliability that does not require an intensive maintenance schedule!

Good point Warren...I change gear oil frequently..well, once a year. That could well be as important, or more important, than the brand of gear oil selected.

So, I guess it's OK for me to use Castrol GL5 80W-90 in the 901 (1970-71 version of a 901 trans) to flush out this old trans I just bought until I get some Swepco (or something)?

And, Paul, the comparison between Swepco and the Torco GL6 was for Swepco that was only 1 year old?

And where do you get the Torco? Or does your PDX shop just put it in?

How often ( years o miles) should I chnge the Swepco in my 915?

Thanks

I use Mobil 1 syn and a quart of lucas stabilizer in my 901. Had a slight grind on the 1-2 shift with swepco if you shifted fast. Now it doesn't grind at all and overall seems abit quieter. I'm sticking with the lucas and mobil 1.

All I know is that the transmission in my Targa is a piece of crap when it comes to shifting. It will actually go into low gear while still moving however will rake a synchro sometime every time I take it for a ride. I have done all the adjustments, new bushings and oil changes. It's nice to know however it should shift a little better when the oil is fresh.

I actually think that 915's used GL-4 stuff.

David Duffield

GL-5 is the way to go with the 915 due to the ring&pinon arrangement.

Randy, I'm assuming that Castrol 80-90 you want to use to flush is a Dino oil. If so, it should work just fine. Others have used similar valvoline with success.

I believe that the issue with synthetic oil in 915s has a lot to do with LSD friction modifier. I'm going to do my own test in the next few months and I'll post the results.

"How often ...."

No matter what mileage, there is a point at which it should be changed. But no oil co. nor Pano or the dealer could tell me what that point is for sure. It is not spendy so I'd do it every 3 years to be safe.

PAG has given various mileage intervals over the years - with the longer ones being for later cars. Now is that because the tranny changed? Or their service & repair experience showed it could be extended? Or because gear oils got better over time? I sure don't know. But you will be quite safe with the short intervals in you owners manual.

Bottom line - for my driving, I do it every 2-3 years and change the brake fluid on the same schedule.

I was using the swepco in my track car and the tranny would not even shift. Well it would for about 5 laps hten i would lose all the gears..


Changed to MOTUL at the track, went out for next session and problem was solved. No more tranny issues. I beleive in the Motul.

Swepco uses a mineral based gear oil with a standard EP additive package that is AGMA and SAE approved. The difference in Swepco's (an independent oil mfg) oil compared to the majors who use mineral base oil is that Swepco also adds a viscous polymer from Shell that is both adhesive and cohesive. It will stick to gear faces even when the oil drains off. This is beneficial for many reasons including reduced gear face wear. The big problem with Swepco over the past few years is that they have decreased their technical staff and manufacturing has suffered a variance in end product consistency. The Lucas additive mentioned in an eariler note contains serval additves with the major additive being the Shell Viscous polymer. The synthetics, although offering up great oxidation stability and better thermal stability than many mineral base oil products may pull the plastisizers out of many seals and gaskets making them weep. Also, certain performance additives that have been perfected for mineral oil based products can not be used very well in PAO or Ester synthetics. Synthetics also do not contain parrifins (waxes) that actually provide a more adventagous "slipperyness" - mineral oils typically contain some parrifins unless sevrely hydrotreated solvent extracted grades. You may want to look at the Chemsearch's Gearco 80W90, Certified Lab's Certop 80W90 or Mantek's Manco 80W90. Primrose and Hydrotex also have good gear oils as well. The majors are shy in additives and support.

Lubemaster:

Here's one for you.....what about non-spec weight?

915's should use GL-5 rated stuff of about 75-90 weight. What are the pros/cons of ( say) a 90/140 weight?

I once did this on a manual transaxle Talon and the cold weather charactrisitcs were hardly different ( only a *bit* stiffer and only for thew first 30-60 seconds)..and the shifting quality was greatly improved. May be placebo effect, but syncros seemed to "grab" better too on this old worn-out car.

---Wil

LubeMaster77, very interesting :)
How does CENPECO fit in all this?

Any idea on the temperature where SWEPCO and others start to rapidly break down?

Anecdotally, I tried M1 in a 915 once for a short period of time, a word of warning to those that think this stuff works well in this application, A 915 w/ M1 likes hurried shifts even less than a 915 w/ SWEPCO:(

Bill, just to clarify, I assume you used over the counter Mobil 1 75w-90, not the SHC?

Bill can you explain what M1 and CENPECO are? Additive pacs? Different brand of gear lube?

Randy, M1 is Mobil 1 Gear oil (synthetic), and CENPECO is another small volume high quality petroleum based oil manufacturer, like SWEPCO is. That's my understanding on CENPECO anyway.

It was awhile ago but whatever the local hot rod shop had on the shelf, silver bottle M1:confused:

Correct, only available locally from 55gal. drums

That's the $64,000 (or $3,000, at least) question.

Ayeah, I was folling the other thread but had nothing to contribute.

The only thing I know is the the Marine transmissions we install run lots cooler than 911s

Now, wait a minute.... that photo of you (which sticks in my head because you closely resemble a chemist buddy of mine - he was cold too in a photo I have of him, long story) was on a sailboat right? And don't sail boaters hate infernal combustion engines.....

Anyway, it sounds like you are going to have to put a pan of Swepco in the oven and heat it up with a temp. probe in it -- if there is an altercation, "burned that chicken up" often works as an excuse.

After a few days offshore in a late season nor'easter you develop an affinty for the things when the engine room is the only warm dry place around.