99 Suburban 2500 Transfer Case

**rowekmr** · 08-18-2009, 03:46 PM

Hello
I have a 99 Suburban 2500 4x4 with the 7.4L engine and push button automatic 4x4 dash switch. Does this have the 4L80E trans? Which transfer case does it have? Mines is making a metallic dragging noise when driving slow and will need some attention and everyone asks which TC does it have and I don't know.

Thanks
Joe

**Z07** · 08-18-2009, 04:53 PM

Posting pictures would be the best way for readers here to identify your drivetrain.

However, you can check your options sticker for these RPO codes:

MT1 = 4L80e (I strongly suspect this is your trans because your engine is a BBC)
M30 = 4L60e (more likely for a SBC and 1500 tho)

NP1 = Transfer Case - (Electric) - Full Range (NVG 263)
NP2 = Transfer Case- (Manual) - Full Range (NVG 261)
NP3 = Transfer Case - (AWD) (Borg Warner 4473)

**rowekmr** · 08-18-2009, 05:15 PM

Its still in the shop (for a speed sensor) so can't take pictures. Where would I find the options sticker? When I called salvage yards for the transfer case they said it was either the NP8 for the 4L80E trans or the NP1 for the 4L60E trans but they are reading from a interchange book I think. I hope it is the NP1 that is one more available than the NP8. Thanks for the info.

Joe

Originally Posted by Z07

Posting pictures would be the best way for readers here to identify your drivetrain.

However, you can check your options sticker for these RPO codes:

MT1 = 4L80e (I strongly suspect this is your trans because your engine is a BBC)
M30 = 4L60e (more likely for a SBC and 1500 tho)

NP1 = Transfer Case - (Electric) - Full Range (NVG 263)
NP2 = Transfer Case- (Manual) - Full Range (NVG 261)
NP3 = Transfer Case - (AWD) (Borg Warner 4473)

**Z07** · 08-18-2009, 05:58 PM

Options stickers are on the inside of the glove box, under the center console lid, and/or on top of the fuel tank :P

But tell me this, how do you shift between drive modes? With buttons (NP1) or with a lever (NP2) or not at all? (NP3)

**2COR517** · 08-18-2009, 06:36 PM

Yes on the 4L80. Or at least it's supposed to.

If it only has 2hi, 2hi, and 4lo, case is NP243. If you have the auto 4wd option, I believe it's the NP 263. I think the B/W 4401 was one ton only, floor shift. Your case has a 32 spline input shaft. If end up putting a used case in, check this closely. The 27 spline 1/2 ton cases area a dime a dozen. I've been searching Craigslist for two months to find a 32 spline unit.

**rowekmr** · 08-18-2009, 11:08 PM

I have button controlled shift buttons on dash with 2wd hi 4wd hi and 4wd lo and auto setting.

Originally Posted by Z07

Options stickers are on the inside of the glove box, under the center console lid, and/or on top of the fuel tank :P

But tell me this, how do you shift between drive modes? With buttons (NP1) or with a lever (NP2) or not at all? (NP3)

**rowekmr** · 08-22-2009, 12:43 AM

Thanks I checked the sticker and there was a NP5 and NP8 code so I guess I have the NP8 which was the one the salvage yards interchange told me I need when I entered the 4L80E and electronic shift buttons options. I had taken the truck to the local lube place and my transfer case was indeed very low (or empty) so they filled it up and the metallic noise did stop but upon getting home and finally pulling the owner's manual out I read that the automatic TC uses a different fluid than the manual one which uses auto trans fluid that they put into mines. So now I have to take it back and have it flushed out hoping it doesn't cause any damage. I tried the 2wd and 4wd which work fine but in 4wd low it didn't move like it was in neutral, at this point don't know if it was caused by driving with it low or with the wrong fluid in it. I will try to sort that out tomorrow.

Thanks

Originally Posted by Z07

Options stickers are on the inside of the glove box, under the center console lid, and/or on top of the fuel tank :P

But tell me this, how do you shift between drive modes? With buttons (NP1) or with a lever (NP2) or not at all? (NP3)

**2COR517** · 08-22-2009, 10:10 AM

You have to use GMs Auto Trac 2 Fluid, from the dealer only.

**Jimmiee** · 08-22-2009, 10:41 AM

If your transfer case won't move in 4 Low it's not the fluid. Don't waste your money on expensive fluid if the transfer case is broken. Pull the drain plug and look for metal. If you have a bunch of metal new fluid won't help anything. Regular ATF may make the clutches chatter but won't do any immediate damage to your transfer case.