185,000 miles, and I think my tranny is getting ready to give up the ghost (2001 Bonneville SSEi, 4T65E-HD transmission). I had the hard shift issue a while back, which went away with Boosty'* shift kit. Now I am getting a howling noise from the front end that a friend (who is a mechanic) thinks might be coming from the differential. I replaced wheel bearings and don't think its the CV joints, but I am not 100% sure. With the colder weather, the transmission is also slipping on take off sometimes; in drive, engine revs with the trans slipping, engages hard unless I back off the accelerator before it kicks in. Doesn't happen again once I drive a couple of miles, but seems be be getting a little worse.

My question is, if I take it in for a rebuild what "extras" should I have done? I know I want the PCS changed, but what other switches, sensors, valves, solenoids, etc. should I ask to be replaced? I also recall reading threads about replacing one of the shafts with a hardened version. What should I make sure gets replaced if I do this?

I am a little reluctant to rebuild a transmission on a 10 year old car, but the engine runs strong, the body and interior are blemish free, the steering is firm, and the suspension is solid. I think there is a lot more life left in her so I am willing to spend some money to keep her on the road.

Absolutely do the following:
Hardened 4th clutch hub shaft (Yours will look bad enough that they should automatically be doing it)
New frictions
New forward band (these are prone to breaking from the factory)
New PCS/EPC
TCC sonnax updates to the valve body

Here'* where the decisions come in.
There are further updates that can be done to the valve body (see tripleedgeperformance.com for more info)
Using other steels or an extra friction to clearance the clutch packs to make them tighter and better actuating.
Harndened input shaft - ZZP'* 4340 has been found to break in build ups. Don't believe what they say about it being 2-3 times stronger than stock. It'* stronger, but not 2-3 times. I'd suggest either their 300M or the Intense Turbine shaft. The downside is both of those are $400-$450, for just the shaft.
I'd also recommend the HV-093 aka Hyvo 5.3L 4T65E V8 chains. They are stronger than our stock chains.

Thanks Bill.