T85 transmission question
 

Encountered unusual behavior today when driving a 57 T-Bird I'm looking at. Trans shifted beautifully, and is equipped with OD, which was operating flawlessly. I know it's a non-sync first, and when rolling up to a stop sign, once I come to a stop it will effortlessly shift into first without protest. BUT- if I'm waiting at a stop light and put the trans into neutral and let the clutch out, when I push the clutch back in and try for first, it will grind at me until the gears mesh and it eventually goes in, takes maybe a second or two. Double clutching does not alleviate this, but I noticed that if I shift up into second gear before trying for first, it will go into first smoothly without issue. Ideas? It only now occurs to me that I did not try shifting into first with the OD lever under the dash disengaged, but I'm not sure that would matter as when the car is stopped the OD is out anyway. Thoughts appreciated- thanks!

Re: T85 transmission question
 

nothing wrong they all do that from time to time

Re: T85 transmission question
 

It sounds like the clutch may be dragging. Check adjustment. Putting into 2nd (synchro) stops the rotation enough to slip it into 1st easily.

Re: T85 transmission question
 

Letting the clutch out in neutral allows the input shaft to spin. This throws the gears out of sync. The shift to 2nd realigns them allowing you to go to 1st again without the grinding. Nature of the beast without a synced 1st gear. My 79 GMC is the same way with its 4 speed. Luckily granny 1st is useless so start in 2nd anyway. At least the way I understand it.

Re: T85 transmission question
 

What 56sedandelivery said is my understanding as well.
Letting the clutch pedal out in neutral grabs the clutch disc and spins the 'front' / input side of the trans up to engine rpm, while the output half of the trans is stopped.
As you discovered, pushing the clutch in and shifting to a synchronized gear (2nd or 3rd) before selecting 1st gear should take care of it. Third might work out better in the long run, to put less wear on the 2nd gear syncro rings. ???

Being able to anticipate the traffic light changing helps you get ready. I often watch for the traffic light for cross-traffic to change to yellow then red just before my light goes green. (allowing for green turn-arrows too) If the light will be changing soon just leave it in 1st with the clutch in. Yes, unfamiliar traffic lights can be a crap shoot for deciding which to do.
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Re: T85 transmission question
 

As stated by those above, The clutch disc is spinning at engine RPM when you press the clutch. The parasitic drag of the transmission is supposed to slowly stop the disc from spinning. It should stop in 3-5 seconds, but if there is abnormal drag such as the clutch out of adjustment, it might not stop by itself and shifting into a synchronized gear is necessary.

Re: T85 transmission question
 

What weight gear lube are you using? 90wt will cause the cluster gear to spin longer thus you have that grinding of 1st gear engaging the cluster gear. I switched to a straight 140 wt back in the 80s and it reduces the time it takes for the cluster gear to stop spinning.

Re: T85 transmission question
 

...and the gear lube should be straight mineral oil with no hypoid additives. Hypoid additives contain sulfur which will attack any yellow metal parts, i.e. the synchronizers. In other words, do not use rear axle lube in the transmission.

Re: T85 transmission question
 

Very interesting reading from some very knowledgeable mechanics. As owner of a 55 Ford with the lighter weight 3 speed o.d. trans , I wsa wondering if the same principles apply to my car. Its NOT the heavy duty T-85.
Thanks for your input.

Re: T85 transmission question
 

An OWNERS MANUAL from 1957 isn't going to give you the correct lube info as the industry has progressed so much -

https://www.onallcylinders.com/2017/...-transmission/

https://en.wikipedia.org/wiki/Gear_oil

Re: T85 transmission question
 

Yup, the same principals apply to your T-86.

Re: T85 transmission question
 

I generally leave the clutch disengaged at a stop but the input and cluster can be stopped by shifting the transmission into 2nd to stop it. Sometimes shifting to reverse will do the job since it works through an idler but it depends on how fast the counter shaft cluster is turning at the time of the gear change. I just find it easier to shift to 2nd then shift into 1st. Use of high viscosity gear lube in an overdrive could be problematic. They always recommended SAE-80 in winter and SAE-90 in summer. I still use SAE-50 grade 100 aircraft engine oil in my overdrives. Motor oil and gear lube are graded differently so SAE-50 motor oil equals SAE-90 gear lube.

Re: T85 transmission question
 

Here's an article about the OD transmission on the CTCI Thunderbird website. It says the same thing...
https://www.ctci.org/servicing-the-o...-transmission/

The recommended oil is GL-1 mineral gear oil, available from NAPA if you can't find it elsewhere. I bought a gallon just a couple weeks ago.
https://www.napaonline.com/en/p/FCA65201
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Re: T85 transmission question
 

"The recommended oil is GL-1 mineral oil, available from NAPA if you can't find it elsewhere. I bought a gallon just a couple weeks ago."

Tractor Supply stocks on the shelf under the name Traveller Ford Tractor Transmission Fluid. It's 90W.

Re: T85 transmission question
 

This lubricant has a GL-1 rating and was last rated in 1995 (inactive). The current (latest) lubricant is GL-4 and is recommended for yellow metals.

I think some of CTCI TECH ARTICLES are dated.

It is like comparing TYPE F to aftermarket FA in AT Fluid.

Re: T85 transmission question
 

Yes they are.
The fellow who wrote and/or compiled them (Gil B.) closed his restoration business a couple years back and isn't as active in the T-Bird hobby as he once was.

Re: T85 transmission question
 

My old 49 thru 51 Lincoln Mercury O/H Manual recommends Medium EP gear lube which was GL3 back in the mid century time frame. GL4 replaced the GL3 many moons ago. Staylube is likely the easiest one to get from NAPA here in the USA but I've had good luck with the AeroShell W100 aircraft engine oil so I just use that. I don't use the stuff marked as "Plus" though since it has a Lycoming additive in it that has TCP. Tricresyl phosphate is about as bad as the sulfuric, phosphoric, boron, & chlorine compounds of the high EP but it's a lot more poisonous.

The 2nd gear bushing, the main thrust washer, and the reverse idler bushing are all suseptiblle to the acidic nature of "High EP" or GL5 The brass syncho blocker rings could likely take the GL5 but those bushings & thrust washer are a different story. The other thing in a Borg Warner overdrive to worry about is the one way clutch. That may slip if too high an extra pressure additive is used a lot.