2001 4wd auto blazer with transfer case being over filled from trans it drips out the seal from the back of the case housing and seal the trans is a little low and the transfer case is over full when it shifts from first to second I can feel the transfer case would it be best to put a new seal or have them tore apart the case is a gm236 with 4 button so I take auto trade still drive it everyday any info would help

 

On my '91, replacing the front seal in the TC solved that problem. It sounds like your '01 is the same way but I am not familiar with them.

 

Like Walleye Hunter said, the seals between the transmission and TC are likely leaking, causing the TC to be overfull. There's multiple seal options, but the best quality one will be bidirectional and have two lips. This situation is fairly common in the S-series trucks.

That being said, the most common cause of this is often a bad vacuum switch on top of the TC, that applies vacuum inside the TC, drawing fluid from the transmission into the TC, and ultimately into the vacuum system. I know this was common in the NP233 TC, but I can't remember if the NP236 has the same vacuum switch.

 

I’ve been driving it for a few months just put it together I didn’t run for years I put a engine wiring harness in it and a whole tube up as I drove it it started dripping ab 4 weeks ago i saw it and I put a new seal and auto track in it I kept leaking I put a new seal and then I caught on that the trans was low and it it was full so u think a rebuilt would be a bad idea or maybe even recommended
I called the shop the guys gonna give me a estimate with just replacing the clutch’s I would have him put a new seal and new vacuum switch

 

I had the vacuum switch go bad on my NP233 (3 button 4wd) and filled my TC right up. I replaced the seals and the vacuum switch, drained the TC to the proper levels, refilled the transmission, and they're both still going strong 100,000km later, and I use my 4x4 fairly regularly for trail riding, hunting, driving in the snow, etc.

Your mileage may vary, and I'd always defer to the advice of a trusted and experienced mechanic.

 

My transfer case runs on the auto track tho and atf can cause damage but I’ve had like 3 shops say that change the seals and the vacuum switch and I should be fine “either they work or they don’t” what one dude said which is kinda tru

 

How do you know that the switch went bad and caused the seal to go bad and not visa-versa?

 

Based on diagnosis information provided by some of the gurus on this forum. I believe it was Swartlkk (Kyle), the forum Admin, quite a few years ago. I have no idea which thread it was originally posted in, but there was actually a GM TSB posted that showed a faulty production vacuum switch, and an updated replacement switch, as well as diagnosis procedures. The switches were colour coded, where I think the original faulty switch had a green dot on it, and the replacements had a blue dot, and a new part number.

EDIT: I found an old thread with the TSB info <CLICKY CLICKY>.

 

Thanks for that info.