Shudder type vibration taking off with trailer

[SMalafy]

I am getting a shuddering type vibration when taking off from a dead start with my 20' trailer in tow when I accelerate quickly or when I am taking off on a steep incline. I noticed last year I would feel this shuddering when accelerating into a sharp corner too with out the trailer in tow. I have tried to repeat this shudder when the transmission shifts to 2nd gear by goosing the pedal, but it will not duplicate the shuddering. Drive line and universals are tight, and I just changed the motor mounts as the truck has 232K on the motor thinking this was my problem and they probably needed to be changed soon anyway.
I am thinking I am getting 1st gear clutch slippage in my 47RH or is my rear axle discs slipping as for a while I had not used the special anti slip lubricant as I have been using AMSOIL in the rear and it never slipped. I recently add the special lubricant last year.

 

[Missouri Mule]

Don't accelerate quickly when you have the trailer behind you especially if it is loaded heavy. You probably putting a lot of stress on converter/ 1rst gear clutch. IF your taking a corner fast the trans mite be trying to shift to a higher gear or it mite be trying to down shift which is more likely to maintain speed.
Hopefully the trailer is not behind you when your trying to fish tail your truck.

 

[cerberusiam]

1st gear in 4XRE is not a clutch or band, it is a sprag clutch when shifter is in D. Try manual first and see if that makes a difference, that will be rear band apply and the sprag is not used. If it does you might have issues with the sprag developing. If it doesn't then the other two clutch packs applied are forward and OD directs. The other issue is axle wrap up and that is the general time you see that problem, high throttle input and heavy load from a stop.

 

[SMalafy]

Thanks for the reply. I went to a transmission shop and had them road test it and he says its the forward clutches.