4L80 No 1st Gear

[Supercharged111]

On the rebuilt trans in the dually, rebuilder is out until Monday night. We were supposed to leave today, then tomorrow, now God knows when. I used to have 1st, now I don't. All other gears work fine. Pull it into manual 1st and all you get is 2nd. I can suffer with it and just drive the 1400 mile journey without 1st as long as it's electrical. Reverse works fine too, so it's not a band or clutch issue. Is there anything else it could be inside that isn't electrical? @NickTransmissions

 

[Supercharged111]

So 1st works when it cools down, I lose it when it heats up despite being commanded.

 

[NickTransmissions]

So 1st works when it cools down, I lose it when it heats up despite being commanded.

Doesn't sound like an electrical issue to me, given you have 1st gear when cold and lose it when hot (as well as not responding to commands when issued by the scan tool) ....

How does your 2-3 and 3-4 upshift feel? Any binding or apparent loss of power upon 2-3 upshift? How about downshifting? Anything unusual happening?

this sounds like a cross-leak between the forward circuit and intermediate and/or manual 2nd circuits (ETA) or possibly low roller clutch in the process of rolling over/failing or worn center support inner race or worn cam segments in the front planet. Was the low roller assembly (as well as the other two "one way clutches") replaced during the overhaul?

 

[Supercharged111]

All shifts feel fine, no apparent loss of power or binding or any of that. It doesn't seem to fade away either, it's just gone. Is the aforementioned cross leakage accessible within the valve body?

 

[NickTransmissions]

All shifts feel fine, no apparent loss of power or binding or any of that. It doesn't seem to fade away either, it's just gone. Is the aforementioned cross leakage accessible within the valve body?

After thinking on it some more, I now suspect it's your low roller one way clutch...Could be wrong but cross leaks should produce other symptoms beyond just no first but if that low roller fails, you'd have no first gear in any range setting.

Was it and the other one-way assemblies replaced (I asked this question above as well)?

Also please quote my post or mention me, otherwise i prob wont see it...

 

[Supercharged111]

After thinking on it some more, I now suspect it's your low roller one way clutch...Could be wrong but cross leaks should produce other symptoms beyond just no first but if that low roller fails, you'd have no first gear in any range setting.

Was it and the other one-way assemblies replaced (I asked this question above as well)?

Also please quote my post or mention me, otherwise i prob wont see it...

I know the intermediate sprag was replaced, I don't think any others were. Would a low roller failure prevent manual low on the shifter (the band) from getting it into 1st?

 

[NickTransmissions]

I know the intermediate sprag was replaced, I don't think any others were. Would a low roller failure prevent manual low on the shifter (the band) from getting it into 1st?

Yup.

See the reference chart below - note the low roller is holding in first gear - all ranges.

I always replace all one-way assemblies in all the transmissions I build, they wear like any other consumables (bushings, frictions, steels, etc). I know of quite a few builders who dont but always thought it was risky to reuse them.

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Not sure Id drive it anywhere. If the overdrive roller clutch also fails, you lose all movement (except in 4th).

 

[Supercharged111]

Yup.

See the reference chart below - note the low roller is holding in first gear - all ranges.

I always replace all one-way assemblies in all the transmissions I build, they wear like any other consumables (bushings, frictions, steels, etc). I know of quite a few builders who dont but always thought it was risky to reuse them.

You must be registered for see images attach

Not sure Id drive it anywhere. If the overdrive roller clutch also fails, you lose all movement (except in 4th).

I was actually just looking at that chart, but I'm being told that, in manual low, the band comes on and can do the job of the low roller. That's not happening, but reverse is just fine. I seem to recall him saying this eons ago back before I had a failed anything as a way to narrow down what's wrong.

 

[NickTransmissions]

I was actually just looking at that chart, but I'm being told that, in manual low, the band comes on and can do the job of the low roller. That's not happening, but reverse is just fine. I seem to recall him saying this eons ago back before I had a failed anything as a way to narrow down what's wrong.

The low roller has to be functioning to achieve first gear, regardless of range position...That said, I wouldn't worry about it at this point as it has to go back to the builder for remediation. Who knows - it could certainly be some sort of leak or perhaps a combo of things...Let him tell you what happened and why. I know it sucks but hopefully he will make it right for you.

 

[Supercharged111]

That's not a question here, time is the constraint.