ATF additive suggestion for 85 Ford C6?

Cubey

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Don't get your hopes too high with with the addition of four quarts of HM fluid.

That's why I'm just considering it. Lubeguard Red might help more and costs about the same. Might not even need to drain any ATF to add the 7oz (1oz per qt of ATF capacity).
 

Cubey

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Tacoma, WA, USA
Here are the pics from when I serviced the transmission a year ago:

Torque converter draining:
20200228_162541 (1).jpg

OEM pan and 4WD style filter it had:
20200305_111857 (1).jpg

Filter removed:
20200305_111703 (1).jpg

New filter installed:
20200305_120539 (1).jpg

New pan installed.
20200305_124623 (2).jpg
 
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That fluid didn't look terrible at all. Lubegard will definitely not hurt anything and it's cheap enough. The dry fill capacity of a C6 is about 12 to 13 quarts so a full bottle is fine.
 

Cubey

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Tacoma, WA, USA
That fluid didn't look terrible at all. Lubegard will definitely not hurt anything and it's cheap enough. The dry fill capacity of a C6 is about 12 to 13 quarts so a full bottle is fine.

Yeah, I was shocked it wasn't too bad looking. It may have been sitting in there for 15-20 years though since it got a lot of upgrades around then RV wise (new fridge, water heater) but then it was severely neglected for the next 15 years and allowed to leak a lot. It's in rough shape RV wise but it's still cheaper to fix wood rot as needed than to buy a new RV. Used RV prices are through the roof right now to the point of it being stupid.

The engine has developed an oil leak that I suspect is the rear main seal but it's not horrific yet. I haven't put any additives in the engine oil yet since it's manageable. I have been using TSC's Traveller oil since it's about the cheapest 15W40 oil you can get when it's on sale.

I'll have the shop do that rear main seal for me whenever the transmission gets pulled out for a rebuild. It doesn't burn as much as oil as much high mileage F250 and the steering gearbox isn't worn out (like they tend to be) so I suspect it's truly under 100k miles.

The differential oil was disgusting and was probably original. I put a reusable LubeLocker gasket when I changed the oil 2 years ago. I have since changed it a second time last year when I was doing rear brake work. I use cheap SuperTech conventional gear oil since it's an open differential, no LS additives needed so it's cheap and easy to change with that reusable gasket. No cleaning off RTV/paper gasket every time and the oil is about $15/gal. The Dana 70 takes just under 1 gallon to fill so it's perfect.

My memory is poor in regards to how much the C6 took to refill. It's odd that the info I was seeing online the other day when I looked up the capacity was saying 7 (5 in pan + 2 in TC) which did seem low. But now some results I'm finding are saying 11-13. Jegs claims 7qts in a stock (RWD?) pan and 2qts in TC: https://www.jegs.com/jegs/jegsautotranscapacity.html It's one of those things where there's tons of bad info out there, I guess.

I went under and did about a 3/4 turn out on the vacuum modulator adjustment screw just to see if it might somehow lower the shift points but changing that part out a couple years ago and adjusting it a few times didn't seem to do a darn thing.

I wonder if the vacuum line to the vacuum modulator is somehow clogged up or a steel line crushed somewhere. I replaced the short hose that connects the vacuum modulator to the steel line down by the trans. I can't recall if I checked for vacuum down there or not. I guess I can look into that since I have a HFT vacuum/fuel pressure test gauge that I carry with me.
 
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Might be interesting to put a 't' in the vacuum line down at the modulator valve and snake a hose up to a gauge in the cab just to see what the vacuum levels look like driving down the road.
 

Cubey

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Tacoma, WA, USA
Might be interesting to put a 't' in the vacuum line down at the modulator valve and snake a hose up to a gauge in the cab just to see what the vacuum levels look like driving down the road.

Ok, well the line down there at the vacuum modulator has vacuum at idle. Dunno if it's how it should be or not, or if the amount is correct. Seemed low but it was steady, like the VRV was regulating it. I tried giving it a tiny bit of throttle in park while looking under at the gauge but the gauge needle didn't move. It might not have been enough throttle required to apply more vacuum via the VRV.

Yeah, I can't really do a proper test without teeing off the line and having the gauge visible while driving. I only idled it today, but I'll be driving it tomorrow so I can report back after that, if the vac mod adjustment helped. But at least we know it has vacuum down there, in some form.

The vac line for it runs up over the C6 bell housing so it's easy to access up top without running a super long hose, I were to try to tee it off.

1622404048871.png
 

Cubey

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Huh, go figure. The vacuum modulator adjustment may have helped. How weird that the new one was exactly like the old non-adjustable one. Could wear I did adjust it before without any improvement. It lowered 1-2 very slightly, about 1-2mph, and 2-3 by about 4-5mph.

The early downshift wasn't as early when I took an exit and mostly coasted to the stop.

I still bought and put in a bottle of Lubeguard red for good measure. Probably can't hurt.
 

Cubey

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Location
Tacoma, WA, USA
It has been about 240 miles since I put it in, climbing bunch of steep mountain grades in Utah and Wyoming where it got me down to 20mph, and the transmission is still acting ok, so that's a good sign I guess.
 
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