For those of you interested in the lengths and sizes for the vacuum hoses that control your transfer case and HVAC that live under the hood of your rigs, here is the list of the sizes and length of each I used on my '99 Blazer LT with 4WD (4-button 4wd/Auto-4wd/NVG236 transfer case). The sizes were determined by checking against parts diagrams, direct measurements, and labels I found on the hoses. For the measured IDs, I used drill bits to determine those by testing the ID of the original hose well away from the end where it would have been distorted by a nipple. The hose lengths are approximate and you should confirm this on your own. If an ID value is underlined, this value was determined from markings on the hose or from the official GM parts description. All other ID and OD values were measured.

There are two hoses for which the outside diameter, OD is important. The first is the one between the adapter union and the Tee. It has a very small ID and must have a thick enough wall not to collapse under vacuum. The second is the short hose, #20, that connects the hose from the vacuum control solenoid to the front axle actuator, #11. On one end this connecting hose, #20, goes over the nipple on the actuator. On its other end the hose from the solenoid, #11, goes into it, using it as a female fitting.

hose between intake vacuum supply and one-way valve: ............................... 7/32" ID, 3/8" OD, L = 20" [light green hose]
hose between one-way valve and vacuum reservoir: ...................................... 5/32" ID, 19/64" OD, L = 8" [light blue hose]
hose between one-way valve and adapter union:............................................ 3/16" ID, 13/32" OD, L = 3" [dark green hose]*
hose between adapter union and Tee: .................................................. ......... 1/8" ID, 3/8" OD, L = 3" [grey hose]
hose between Tee and vacuum control solenoid: ............................................ 5/32" ID, 5/16" OD, L = 2.5' [red hose]
hose between vacuum control solenoid and axle actuator: ............................. 5/32" ID, 5 /16" OD, L = 4.5' [dark blue hose]
hose into which vacuum line from solenoid connects to axle actuator: ........... 5/16” ID, 9/16" OD, L = 1.5” [orange hose]**
HVAC supply line (goes through firewall): .................................................. ... hard plastic hose with female molded coupler [purple hose]
brown cable: .................................................. ................................................ front axle actuator cable

Christine

Hint: If you want a bit of extra insurance, you might do what I did and use zip-ties as mini hose-clamps where each of the hoses attach to the nipples. For the connection to the axle actuator, I used spring style fuel filter clamps.

*The GM part description calls for a 7/32” ID hose.
** The GM part description calls for 8.3mm ID hose.

Exploded Diagrams used to make diagram with part numbers:
https://nemigaparts.com/cat_spares/e...t/06/ts06-500/
https://nemigaparts.com/cat_spares/e...t/03/ts03-536/ (B)
https://chevrolet.7zap.com/en/s10/51...oner+controls/ (C)

Original thread: https://blazerforum.com/forum/2nd-ge...replace-95425/

 

Thank you for this updated re-post. This is very timely for me.

 

Excellent! I was hoping it might be of use to other people.

 

Christine, are there any write ups like this for the 3 button?

 

I'm not sure. Another member might have been wanting to do it. I was thinking I might do it myself as I might have the diagrams.

 

thank you so much but please don’t go out of your way for me. I feel pretty confident I understand but if you had done an in depth write up on it also I definitely would have looked over it. however as informative as the other write up was i’m sure there are plenty of people who would benefit from it. thank you so much for your reply.