On the build sheet for my truck , it says I have the "corporate 9.25 LD rear axle". Is the limited slip additive required? I know the LSD is limited slip diff. But with no tag on the cover I dont know for sure if the rear end has been replaced or not.

 

And the tranny ? is as follows. I have the 46re trans, is it normal that when I pull out from a light or whatever ,it shifts into 2nd like normal , then 3rd like normal, but after a few seconds I feel it shift into a fourth gear! Is this just the converter locking up? It feels like it is going into OD, but the OD is off.

 

And BTW, when the overdrive is on it goes into a fifth gear. I know a 46re is a 4 speed automatic, but does that include OD or not?

 

The 46RE should have 3 years and then overdrive.

 

Well something is wierd because it has 4 gears plus OD.

 

You sure it has 4 gears and then overdrive and your not just feeling the tc lock up or something?

 

the 4th gear you are feeling is the tc lockup. if you have a tach, you'll see about a 300 rpm drop when it locks. you'll also feel a little more drive line shudder with it locked, since the tc can't slip. the OD shift is a much bigger RPM drop.

i've read there are two different versions of pcm programming that controls the trans.
the older version shifts like this. (my 01 does this).
1st -> 2nd -> 3rd -> tc lock -> OD.

the newer version supposedly shifts like this, and only locks up in OD.
1st -> 2nd -> 3rd -> OD-> tc lock


the 46re is 4 gears, including OD, and doesn't count the TC lock.

if your build sheet and/or glove box sticker or underhood sticker don't say LSD, then you probably don't have it unless the truck has a lot of off road type mods. look on the axle tube drivers side for the part number sticker. mine still says... 3.55 OPEN. open=non lsd.

you can tell for sure by removing the diff cover and looking. the open dif has an open carrier and spider gears rotating around. the lsd has the funky looking contraption, and if its a stock craplok lsd, likely has pieces of springs and clips laying in the bottom. no additive is required for an open diff. anything rated for GL5 including 75w90, 80w90, 85w90, or 90w, or 75w150 is fine.

 

The manual says to use 80w90 in the rear end and 75w140 in the front. I try to stay as close to those as possible.

I have an open differential.

 

Thanks all. I figured it was the TC locking. It really sucks power wise when it locks. If I drive normally it locks at 40 mph and bogs the truck badly. I will look into getting it flashed for the newer shift array.

 

ask the dealer about this shift sequence and verify what i said above, because i'm only repeating what i heard. and (obviously) remove your hypertech programming before a flash update.

let us know what you find out. i'm interested too. mine also bogs at 40 with tc lock and shifts to OD at 45 if i turn it on.