Thread: ATF history/evolution lesson required

OK, first up, all ATF's are friction modified.
The differences are the type of friction modification, ie. does the mu (coefficient of friction) increase or decrease with increasing clutch face speed.
This is the fundamental difference between the old Ford M2C-33 and Dex II specs.
BTW the M2C-33A/B was introduced in 1959, M2C-33C/D spec dates to 1961, Type 'F' was introduced in '67 and Type 'G' in 1972.
Which one do you want ?
IMO they are all outdated and not relevant as Ford superceded them all in 1974.

ATF Fluids - Bob Is The Oil Guy

Brief History of ATFs - Bob Is The Oil Guy


Personally I'd run an MTF like Castrol Syntrans B or Syntrans Max, Redline MTL, Amsoil MTF, etc.
IMO there is no place in a manual transmission for an ATF, the MTF's have the correct coefficient of friction for good synchro operation and have a more robust additive package for the types of gears and bearings used in manual gearboxes.
For correct synchro action you need the coefficeient of friction of the lubricant to increase as synchro cone and clutch face speeds reduce.
Engine oils for one don't do this, so you will get the familiar 'crunch' at the point of engagement as the two surfaces 'slip' against each other rather than normalise their rotational speeds and engage their repective dogs.
I suspect this may happen more easily with Dexron type fluids than the ancient Ford spec too.

Originally Posted by windsock

G'day,

Just had an old 1984 LT77 mainshaft rebuilt in a box with 190,000km on it and am now wanting to re-oil it to the best standard possible.

To this end, I am slightly perplexed by the vast assortment of discussion and apparent contradictions within the myriad array of forums and other sites on ATF oils and LT77's. I have indeed searched this site but still am not clear on some things.

I have no confusion about whether to use an ATF or at least an ATF 'like' fluid (as specified then by LR and currently by the likes of Ashcroft, Difflock et al) but where my confusion arises is in the many and varied standards of oils out there now and how these relate back to the standard required 'back-then'.

Back in the days of this trucks manufacture (1984) it was specifed an oil to M2C-33 standard. My research indicates this was/is a non friction-modified oil. So, some specific questions and I hope for some answers in layman terms please...

What has happened to ATF oils since 1983 that gives rise to their current state? How have the oils evolved since then? (I have tried to find this out online but there is no one clear description of how oils have evolved from what they were then to what they are now; and what that means for LT77 gearboxes designed and running since 'back-then'.)

What else (if anything) was/is it that got it (M2C-33) chosen to be the original specification? Simple availability? What was the alternative?

Are the modern Dexron 3 oils friction modified?

Why is it that some ATF oils state specifically "suitable for all gearboxes except those requiring M2C-33" - Castrol Transmax M - which incidently is what Castrol manuals here in NZ (Supercheap stores) recommends for LR LT77 boxes!

If so, how does this affect the running of the LT77, given the original spec was for a non friction-modified oil?

The driving force behind these questions is the gearbox 'rebuild' just paid for and the desire to start off with the right specification ATF oil.

Please, I'd like to keep this thread to LT77 and ATF or ATF-like discussion. I have noted some discussion seemingly talking cross-purposes with confusion between LT77 and the R380 oil tech bulletins.

Cheers for any responses.

Phil

Plil I hope you now have a X drilled transfer gear in it. The early ones were a sod for not oiling.

I have mostly run ATF and now run MTF in my 84 and SAE 75 in the transfer. At one stage I had SAE 75 right through but it stuffed the oil pump in winter as the oil got to heavy and it was also heavy to shift. I now run MTF in the LT77 and ATF right through the LT95 as the oil gets past the seal between the boxes. If the seals are good I try to run a SAE 75 or 90 in the Transfer. I had no other problems.

I've found main thing in the LT 77 is getting oil to that shaft some how rather than using fancy oils.
As you may know don't use any thing to heavy as the oil pump will fail.


Cheers Tony

BTW, the "is NOT recommended where Ford M2C-33F or G fluids are specified." is for auto tranny operation for old transmissions requiring the M2C-33 spec fluid.
You can't use a GM spec Dex II/III/IV/VI in them.

As Tony said, the viscosity is critical too, particularly in cold weather with the pump in those old LT77's, so don't use a mineral based MTF where you are either, it could end in grief.

Thanks a lot for the quick replies, very much appreciated. I am in the workshop at the moment replacing a clutch kit and a rear mainshaft oil seal that is leaking after the mainshaft rebuild Once I've got both those sorted and reinstalled, I will be checking oils aside from the Valvoline ATF Dexron 3 I have here in the shed already.

Originally Posted by rick130

BTW the M2C-33A/B was introduced in 1959, M2C-33C/D spec dates to 1961, Type 'F' was introduced in '67 and Type 'G' in 1972.
Which one do you want ?

M2C-33 F or G spec'ed oil's are listed in the old Land Rover one ten manual I have here. If they're superceded so be it.

Your second post...

Originally Posted by rick130

BTW, the "is NOT recommended where Ford M2C-33F or G fluids are specified." is for auto tranny operation for old transmissions requiring the M2C-33 spec fluid.
You can't use a GM spec Dex II/III/IV/VI in them.

...cleared up a massive amount of confusion for me. Silly bugger I was forgetting these were originally for Auto Trans and was assuming the same directive stood for the LT77 also, Doh!

Originally Posted by Rangier Rover

Plil I hope you now have a X drilled transfer gear in it. The early ones were a sod for not oiling.

Yes, I am. I went to a 25D 1.410 ratio transfer box recently and had the supplier cross-drill the gear. Works a treat as when I pulled it all apart last night to replace the mainshaft oil seal, there was transfer box oil over the mainshaft splines as it should be. Old splines on the old 1.667 ratio transfer box and mainshaft were 50% gone... nice to drive a truck with minimal backlash again.

Originally Posted by rick130

Personally I'd run an MTF like Castrol Syntrans B or Syntrans Max, Redline MTL, Amsoil MTF, etc.
IMO there is no place in a manual transmission for an ATF, the MTF's have the correct coefficient of friction for good synchro operation and have a more robust additive package for the types of gears and bearings used in manual gearboxes.
For correct synchro action you need the coefficeient of friction of the lubricant to increase as synchro cone and clutch face speeds reduce.

Originally Posted by Rangier Rover

I've found main thing in the LT 77 is getting oil to that shaft some how rather than using fancy oils.
As you may know don't use any thing to heavy as the oil pump will fail.

OK guys, next question is based on the recommendations above re the MTF's. If I am to look for an MTF here in NZ what 'weight' oil to look out for? Any brands to look out for over others, bearing in mind I have yet to see Pennzoil, Redline, and most of the range of Penrite here. Castrol, Mobil and Valvoline are basically what I can readily find.

Cheers,

Phil

First off, these bloody gearboxes, both the LT77 and R380 can be very idiosyncratic, what one 'box and owner likes, another doesn't care for...

Now the disclaimer is out of the way I would pick one from the list here Low Viscosity Manual Transmission Lubricants
JB, who has listed these uses Redline MTL in the LT77 in his 90 and loves it, and he's in Canada, so there is no problem with cold weather operation in terms of viscosity and the pump.
The SAE 'weights' are actually a range of viscosities within a certain range, you can see from the chart on JB's MTF page where they range from and how they compare to an ATF.
The critical thing when comparing to an ATF is the cold viscosity, so be truthful about how cold an ambient you will ever see, and when you have the relevant specs of a fluid you can plug the numbers into this calculator Viscosity and Viscosity Index (VI) Calculation to see how they compare at your lowest ambient. We want something that won't stress the pump gears too much, but still provide adequate fluid viscosity when hot. (I often see over 75*C just cruising down the highway with my R380)
Also remember that while a fluids viscosity has a bearing on shift performance, the friction modification also has a huge influence on how the synchros behave. Thinner isn't always better.
I found that Syntrans 75W-85 shifted far better in my R380 at -7*C than Caltex MTF-94, even though the MTF-94 was a thinner fluid at that temp.

Redline MTL 70W-80 is available in NZ as racers there use it. It'd be one of my first choices, although some report it isn't as nice as an ATF when cold on the first few gear changes (but better when hot)

Amsoil MTF 75W-80/5W-30 has very good reports from users in NA in a wide variety of gearboxes. It's hard to find on this side of the Tasman, not sure what availability is like over there. I have reports from the US where people prefer it to R/L MTL in certain applications. It's also a newer formulation.

Castrol Syntrans B 75W-80 is a thinner formulation of my favourite recommendation for the R380 (Syntrans 75W-85) Syntrans B is formulated for the 'box in the XR6 Turbo and is quite a bit thinner than regular Syntrans, so it should be a good candidate for the LT77. Having said that, a mate of mine and occasional poster on here has run the 'old' Syntrans in his LT77 for years now and reckons it's the best fluid he's ever used, but South Australia doesn't get Kiwi cold either.....
Syntrans Max should work well too. It's formulated for ZF light commercial 'boxes and sits sort of between Syntrans B and Syntrans 75W-85 in viscosity.

Do a ring around and see what you can find. Be prepared for some sticker shock too, but it's worth having a good fluid in the gearbox. A manual transmission gives the fluid a fair bit of a caning, often shearing additives like viscosity index improvers in short order. (the lower the quality of base fluids, the more additives like VII's have to be used)

As Rick said the box's can be very picky as to what they like,my R380 only likes ATF or MTL,nothing else.I'd plum for MTL as I've personally seen how much longer it makes gearbox's last. Pat

Fantastic reply thank you Rick130. Very useful bits of info.

Questions here and there though...

Originally Posted by rick130

We want something that won't stress the pump gears too much, but still provide adequate fluid viscosity when hot.

What is too much viscosity? In the older LT77 the pump has fibre components I understand but which ones I know not so I guess I need to be especially careful here uhh?

Originally Posted by rick130

Also remember that while a fluids viscosity has a bearing on shift performance, the friction modification also has a huge influence on how the synchros behave. Thinner isn't always better.

OK, are there two numbers to look out for here when reading specifications? Viscosity I think I understand - cSt(at)40C and sTc(at)100C right? What about the friction modification, how to tell what this is? Is it generally listed in specs as a number or is it simply pour it in and try it out for 10,000km? When we are discussing ambient temperature we are using ambient air aren't we or gearbox oil temperatures?

You see ambient conditions up to 75C?!

Originally Posted by rick130

Castrol Syntrans B 75W-80 is a thinner formulation of my favourite recommendation for the R380 (Syntrans 75W-85) Syntrans B is formulated for the 'box in the XR6 Turbo and is quite a bit thinner than regular Syntrans, so it should be a good candidate for the LT77.

Sounds like I should see if I can find some perhaps...

Originally Posted by rick130

Do a ring around and see what you can find. Be prepared for some sticker shock too, but it's worth having a good fluid in the gearbox.

Agreed for sure. After having the box mainshaft rebuilt I have a bit of immunity to sticker shock... wife still gets a shock when she looks at some of my invoices though

Just about got the gearbox back in the truck after replacing the rear mainshaft seal. Was leaking at a rate of 200-300ml per 300-400km. Also replaced the clutch with a whole new kit so will be good to go and will certainly be trying various oils in the truck over time to see which one is best.

Last question for this morning. If/when I try an MTF, and should that MTF disagree with the LT77 palate, what are the likely signs to be nervous about and what are the signs to be dreading? Obviously, easy gear changes is the objective (and longivity) but are there any signs I should be wary of? I am quite deaf so noises can be an issue for me if I have to distinguish one from another...

Cheers,

Phil

Firstly, on a P/TDS you will have the viscosity @40*C, probably 100*C and the Viscosity Index.
If any one of these three numbers are missing, we can calculate the other with that Viscosity Calculator I linked to, and from there any viscosity with accuracy down to around -10*C. below that it all goes out the window....

I believe the pump isn't as strong in the LT77 as the R380 and so we have to be a little more careful with the fluids used and the minimum ambient the box will see/used in. Everyone talks and warns about it anyway.
Maybe we should PM Dave Ashcroft and ask ? (and Ashcrofts still recommend ATF, either Dex II or Dex III in these boxes, but they recommend a supplement too. )
Having said that, I think it may have been a carry over from the LT95 (LT85 definitely uses a different pt.#) which used engine oil (15W-40) Funnily enough a 15W-40 engine oil is exactly the same viscosity as a 75W-90 gear oil, so go figure.......

I know Redline MTL is safe to use in Canada, which should get a damn site colder than NZ, and as I've said before a mate uses Syntrans in his, but South Oz isn't NZ either.
What sort of low will you see in winter ?

Re the frictional characteristics of fluids, it's very much a suck it and see deal. There is no info on a data sheet that will tell you, and MTF's do vary a bit in their characteristics as synchro's and gear rotating masses vary so much. All I know is that the majority of people who have used Castrol Syntrans in the R380 like it, a couple who have used it in the LT77 like it, and those that have used Redline MTL are split. Some reckon it's the best thing since sliced bread, like Pat does with his R380, others are pretty ambivalent to shift characteristics. I found it pretty baulky when my R380 got really hot.

Our objective is the least wear with the best shift characteristics. Measuring wear isn't easy, it takes multiple used oil analysis to do it, but gauging the feel of the the gearshift is obvious.
Remember when changing fluids it can take up to 800km or so for the new friction modifiers to embed themselves into the clutch and cone surfaces. The first few days of gear shift may be quite contrary then get better, other times it can be immediately better.
When I trialled Torco RTF, a very well respected race gearbox fluid from the US, I had every gear change crash on me for three days straight. Every down change had to be double de-clutched and rev matched exactly, and the up changes were horrific, going crunch every two out of three shifts.
I was about to dump it on the third day (nearly $75 worth of oil) and it just came good Changes aren't quite as slick as Syntrans, but there are less whiskers on the drain plug magnet and it all but eliminated the hot gear rattle I used to have in summer. I think it might be too thick for the LT77 though. It's a 75W-90.

You see ambient conditions up to 75C?!

Alright, that one is a gearbox temp, when I was talking ambient, I meant ambient.