I'm In Conn, my Blazer is in NY. Before I go NY Can anyone tell the Vacuum hose sizes I Might need to fix most under hood & 4x4 issues.(Damn the chipmunks) I'm taking a new actuator & transfer case vacuum switch with me. Is silicone better than rubber???

 

Here are a couple threads I created to help with this.

https://blazerforum.com/forum/articl...m_content=post

https://blazerforum.com/forum/article-submissions-discussions-47/underhood-vacuum-lines-3-button-nvg233-transfer-case-rpo-np1-107596/?utm_source=share-link&utm_medium=button&utm_campaign=share&utm_cont ent=post

 

Wow!!!! Christine this was incredibly helpful.. I was taking 20 feet 7/32 & 20 feet 5/32 hose, just wasn't sure if I might need anything else being in the middle of no where with the closest parts store closed on Sundays. My 92K mile 2000 Blazer is mint underneath & all the hoses are still like brand new except for the fact Chipmunks turned into a Habitrail for themselves. despite sticky traps & bait bits Thank you so very much for your help is much appreciated. Willie (toys)

 

You are very welcome.

The quality of the rubber used in these hoses was not consistent. I had to learn all about them the hard way. LOL

It is nice to know that whthaI learned could save others a bit of hassle.

 

Did GM ever upgrade the 4wd hose system? I had a 98 4wd, and the hose **** show with it leaking into the HVAC system was a nightmare! I had little success fixing it's issues. I had that puppy for 20 years, and loved it, but in the end it just had too many problems to save it, and it went to the junkyard. I just wondered if that terrible problematic hose situation was addressed before that model was discontinued?

 

What you are describing was a failure of a few different systems, one of which involved the vacuum switch on the transfer case itself which would then contaminate the vacuum system and I'm not even certain that the switch had to fail for it to allow fluid to pass through it as I am certain it was never designed to be submerged in fluid, only the occasional splash of fluid. For the switch to allow fluid to pass through into the vacuum system, first the input seal on the front of the transfer case would need to fail, which would then allow transmission fluid to push into the transfer case, over-filling the transfer case. Wear & age had a lot more to do with it than anything that would have prompted an upgrade or redesign from GM. Although they did change things around on the NP236 transfer cases with the move to an electronic switch up on the firewall with the Auto4wd option which was more because of the way that system worked than any potential problem from the previous system. This type of problem did not really present itself until many years down the road so there was no real correlation between the NP236 electronic switch and this 'issue'.

One way to stay ahead of it on the NP233 models is by periodically removing the transfer case fill plug to monitor transfer case levels at engine oil changes which would go a long way to stay ahead of input seal failure and definitely away from the point of HVAC contamination. If fluid pours out of the fill plug (upper of the two plugs on the back of the t-case), then the input seal is likely allowing transmission fluid to flow into the t-case. The transmission is also likely low by that same amount of fluid which is also a very good thing to know.