Cracked t-case np236
 

I'm new on here. "Does anyone know of a heavier duty t-case, or a better way I can attach my front drive shaft to the t-case, or a way I can disengage the front drive-shaft so it only turns on when i'm off-road?" I have a 2000 Blazer 4x4 4door with the 4switch dash control for the transfer case. It is a NP236. So from what I've gathered it pretty much is an all time 4wheel drive in a sense that both drive shafts are always rotating. The blazer has a 4in. lift. My transfer case is cracked next to the shift motor where there is some little thin support plates (kinda like gusset plates). The front drive-shaft has a double cardon joint right next to the transfer case. The joint begins to wear, which causes vibration, which in turn works a on number on the t-case. So if anyone has an idea for a solution it would be appreciated. I'm also looking for a diagram of the np236, I might take it apart and find someone that can weld that magnesium case.
Thanks

you have the "Auto 4WD" system, so it shouldn't be running the front shaft all the time. if it is, it's either because you're leaving it in "Auto" mode (which i don't think it's actually supossed to do), or there is something wrong with your TCCM or wiring.

i don't knw how it could've broke the t-case by being engaged all the time, i used to do 7 grand lauches (in 4HI) in my '92 Jimmy, and i never had an issue with the t-case. ever.

can you snap a pic & post it up here of the damage?

oh yeah, the case isn't magnesium, it's aluminum.

**edit** sorry, after reading it over, i notice it sounds..........."wrong" where i said, "you're leaving it in "Auto" mode (which i don't think it's actually supossed to do)". i meant it to be taken as.......i don't think the front shaft should be running when in "Auto" mode.

but i'm no expert on these 4 button systems. hopefully swartlkk will get around to seeing this post (he kinda our resident expert). but be patient, he's only human (we think) and he's usually quite busy.

GL.

The clutch pack in the NV236 transfer case is preloaded which does mean that it will always turn regardless of whether it is in 2HI, 4HI, Auto4wd, or 4LO. It doesn't mean that it has load on it though since the front axle is only engaged in any of the 4wd modes, including Auto4wd.

Sounds to me like your joint failed and took out the case due to the vibration. It must have been bad for quite some time to do that though. Had the joint been replaced sooner, it likely would not have done damage to the case.

In terms of getting a "stronger" transfer case or one that doesn't turn the front driveshaft in 2HI... That depends on how much work you want to put into it. Dropping down to the manually shifted NP231 would take all of the electronics out of the equation. The NV233 would require swapping out some wiring, the dash switch, and the TCCM. I'm not sure if there are size differences between the s-series NP/NV23x transfer cases and the fullsize truck NP/NV24x transfer cases. NP241 is the big brother to the NP231. Similarly, NV243>NV233 & NV246>NV236. I just have never heard of or read about people swapping them into the s-series trucks.

It has happened before and I had the joint replaced, that was little over a year ago. I greased the joint as often as I replaced the oil if not more. If replacing the t-case to a different one and making it all manual fixes my problem then it really doesn't matter how much work is involved. I'll see if i can find the pictures later today and post them up. Thanks for the reply's

thanks for the correction Kyle.

and it makes sense (of course). how else would it be able to automatically detect slippage on the road surface otherwise.

sorry, just rambling off to myself................:icon_shrug:

Sorry, i'm having a little trouble figuring out how to post pics on here. I have a buddy that is good with computers, he might be able to help me post them. Sorry!
Does the three button t-case spin all the time like the 4-button t-case? You mentioned a couple of other t-cases in your reply, is one of those the three button dash switch t-case, or are they totally different? I'm just brainstorming kinda wondering if these other t-cases will fit in the transmission in my current 2000 Blazer LT 4dr.

The NP233 front driveshaft should be free wheeling when in 2HI.

The NP231 & NP233 will bolt up to your transmission. You will want to make sure that the cross member is the same between them, but other than that (which I do not think anything changed), they should just bolt in.

Now, with the NP231, it is all manual. You will have to install a floor shifter in the truck to actuate the transfer case. There will be some wiring that you will have to run up to the front axle switch for the front axle engagement light, but other than that, it is the simplest swap as well as the most robust. Gets rid of all of the electronic controls.

The NP233 will require some rewiring as it has the electronic controls, however, very little is the same as what your current NV236 uses. The TCCM, dash switch, encoder motor, and most all of the wiring between the three are all different.

If I switched to the np231, if i'm thinking correctly the only wiring that I will need is what activates the the front differential which engages the front axle with the front drive shaft?

No, there is no wiring that actually activates anything to do with the 4wd. The only wiring is for the light in the console on the floor that tells you that the front axle is engaged. This will run from the switch in the front axle back to the console.

You will need to redo the vacuum system so that it runs back to the transfer case. The current vacuum setup does not run back to the transfer case, but to an electric solenoid on the firewall. The vacuum system is the same for the NP233 as it is for the NP231. I have posted a diagram showing the NP233 so you should be able to search for "NP233+vacuum+diagram" or "NV233+vacuum+diagram" and find it. NP = New Process & NV = New Venture. They are really one in the same as the name changed sometime in the 90's.

ok, just so i'm (we) are clear.

if a truck has the 3-button NP233 t-case set-up............it'll have the same vacuum set-up as the manually shifted NP231 t-case?