Disappearing Reverse Gear - 727 trans 340 Challenger

[Garp]

Had a great and informative day with Justin "Dart Vader" @ his workshop today and managed to sort out my Challenger oil pressure gauge.
He also picked-up that my thermostat was shagged which would explain my very very static temp gauge ..... thanks mate, I learned a lot today with that chat and look around an engine bay.

Now, however, I need to diagnose the thing that seems to be getting worse with use - my reverse gear is disappearing !
If I engage reverse whilst stationary and on the flat, it'll come on very gently if I "feather" the accelerator peddle a bit at a time - give it too much and its like I'm in neutral. If this happens, I have to engage Drive, shift forward a tad, engage reverse and bring it on slow again.
I don't want to put my foot down too much in case the gear engages and I don't have room for the result ....... She goes forward fine and shifts through smoothly ....tell me this is an easy fix ?
Any help appreciated
Cheers
garp

[latil]

Sounds like band adjustment. Check fluid level and colour first off.

[DaveBishop]

I sounds like the band needs to be adjusted. You will have to take the gearbox sump to do it.

[Garp]

Sounds like band adjustment. Check fluid level and colour first off.

Liking the sound of this .... tranny fluid needs to be checked HOT, I know, but what colour am I hoping NOT to have ???
thanks

[Garp]

I sounds like the band needs to be adjusted. You will have to take the gearbox sump to do it.

So you are saying that there is no need to drop the 'box? It can be done drained and GB sump off ?
Sounds encouraging !

[latil]

Trans fluid should be the colour it went in,clear red.

[MilesnMiles]

Check fluid first, low fluid tends to affect reverse especially when cold.
If that don't work, listen to Mr Bishop!