[Headskabob]

My 93 suburban started having this issue where when I'm driving at highway speeds and I let off the gas the rpms drop like I'm in neutral drives normal at other speed no hard shift

 

[blackburb]

2x4 or 4x4?

 

[Headskabob]

4x4 sorry lol 5.7

 

[blackburb]

Have you checked trans and xfer case fluid for level and condition?

 

[Headskabob]

Yeah both lvls are fine color is fine on transmission

 

[blackburb]

This is a long shot, but when my t-case had a hole in it and needed to be rebuilt, the mechanic forgot some thin plastic shims inside and it did exactly what you're describing. Whenever there was an engine braking situation (torque entering the case from the tailshaft), it neutraled out. As soon as I gave it a little gas, it re-engaged and was fine. I drove it several hundred miles like that towing my 6000lb camper and it was none the worse for wear when he took it back apart to fix. I don't even know if your 93 uses the same case, but it's possible they disintegrated from age/miles, but that's not something I've heard of as being even remotely a common occurrence.

 

[Headskabob]

That is exactly what it's doing I was thinking something with the torque converter but that what you described is exact

 

[blackburb]

Hopefully some of the smarter guys will be along this evening with their thoughts. I've had a few trans failures over the years, but they never did that.

 

[Headskabob]

I think your right I had the transfer case rebuilt like 2 months ago

 

[RayVoy]

Like the OP, my 1st thought is torque converter