Transmission Slippage from a stop

A little background info on a 2000 5.3l, 2wd Silverado. I have a leak at the rear main engine seal. After looking at it on a lift with a mechanic friend, it appears that the seal is pushed out from the seal bore and might be contacting the flywheel. It is not pouring out, but is dripping. With this in mind, I thought it would be a good idea to have the transmission rebuilt at the same time, since the truck has 186,000 miles on it and the tranny will be out. My mechanic friend takes transmissions to a guy at a local Chevy house to have them rebuilt and has offered the rebuild and the rear main seal replacement for around $1200.

I sometimes have problems with the truck not wanting to move from a complete stop, then it starts to take off as the RPM's climb. I don't notice this in any other gear changes. So I am armed with as much information as possible, my questions are: Will a simple rebuild (i.e., clutches, springs, bands, seals, etc.) take care of this particular problem, or is there something else to look into. I really don't know how the transmission actually works from idle at a stop, to actually starting motion. Could this be a pump problem and is this something that will be addressed in the rebuild? Thanks for any information!

Sincerely,
Matt

the transmission if not properly maintained by replacing the fluid/filter every 40,ooo mi gets worn. the fluid turns to acid the particles increase then the valve bodies wear out. a simple rebuild will not help. the transmission needs a complete inspection and then a cost to repair should be given. quotes now will ensure a poorly performing transmission.

186,ooomi is high. parts will be worn. dexron III did not help with this aged tranny. new dexron VI or mobil sythetic transmission fluid should be used.

rear main seal leaking / migrating could be worn crank bearings.

the transmission if not properly maintained by replacing the fluid/filter every 40,ooo mi gets worn. the fluid turns to acid the particles increase then the valve bodies wear out. a simple rebuild will not help. the transmission needs a complete inspection and then a cost to repair should be given. quotes now will ensure a poorly performing transmission.

186,ooomi is high. parts will be worn. dexron III did not help with this aged tranny. new dexron VI or mobil sythetic transmission fluid should be used.

The transmission has been serviced at regular intervals while I have owned it, but I do not know what service was done to it by the first two owners and 80,000 miles. I do know that it had a fifth wheel hitch on it, but was removed, and it did not come with the tow package, 3.73 gears or transmission cooler. I added a reciever hitch, wiring harness and tranny cooler after I purchased it. So, I am not sure what kind of work it did before I purchased it. I'll call him up a little later today and see again what the rebuild/diagnosis entails and then go from there. I was trying to get an idea on how the transmission goes from idle to forward motion in first gear. Thanks again for the info!
Sincerely,
Matt

rear main seal leaking / migrating could be worn crank bearings.

So this could be caused by the crankshaft moving? Can they inspect this endplay with the transmission out, or is this something only confirmed in a teardown? Unfortunately, I don't have the money to do anything other than the transmission and seal change out, so another engine would be out of the question at this time. I do know that it has always had regular oil/filter changes every 3,000 miles.

since you owned this vehicle what was your fluid/filter maintenance intervals. what type fluid did you use ?

slippage is from fluid pressure loss . this is from worn parts. could be cracked sun shell etc.

if you replaced the fliud/filter at 80,ooomi and repeated every 40,ooomi. and used synthetic transmission fluid I would say wear would be min. sun shell however still can be cracked. too much heat / defective part . many have had the sunshell cracked.