Allison Possible Rebuild/upgrade

[MEGA14]

I have a 2002 Silverado CC Commercial Vehicle w/8.1/Allison.

 

Recently it has been shuddering slightly off the line , has a delay shifting into D with a light clunk and when WOT and approaching 80 - 90 MPH , a pronounced rattling noise is heard and the Allison hesitates to shift into 5th .

 

I figure I'll be looking at some sort of repair/rebuild .

 

I have done some searching and found sites like Hill Killer Performance Transmissions and a couple of others .

 

The prices , when compared with the actual value of a 2002 Silvy , to rebuild the Allison to not break again ( or as easily , relatively speaking ) is very high . About $3000-4000 .

 

I know I'll need to roll up to a Trans Shop or a GM Dealer to get an actual diagnosis but in the meantime , what have you Folks found to work as upgrades and/or the trustworthy Trans Builders ?

 

I am in Canada but would consider shipping the unit or driving down for a re & re in return for quality work and expertise .

 

I've also read a little about Trans Kits but don't know whether I'm beyond that but I doubt it .

 

Other than the slight shudder off the line and the WOT 4th to 5th shift noise , the Trans shifts nice and smooth .

 

A while back , I did pull an older GM 1500 EC 4X4 out of a ditch while in PARK with the Truck ( no winch ) .

 

I did feel it slip a second or 2 but it then gripped and pulled it out .

 

I regret having done that because I feel that's what has caused these problems .

 

Trouble is , I had it in my head the Allison was bulletproof so a 1/2 ton truck seemed harmless . Wasn't much of a grade , either .