fields_mj
Full Access Member
Replaced my vacuum pump last week and ran into a few issues that I thought others might like to know about. In short, before you get too far, measure the diameter of the vacuum pump shaft and make sure that the replacment part has the same size shaft. Otherwise, you might get the old one off only to find out your replacment won't work with the existing pully.
Here's my story:
First off, I called the local parts store, and they didn't have anything in stock. The part they could get me was a rebuilt Cardone. Rock Auto had the same pump for $40 less, so I bought it from them. When I got it, the shaft on the pump was a smaller diameter than the original. The original measures 0.669" with a pair of calipers. The replacement measured 0.650". There was actually a small step very close to the pump where it looked like an extra grinding operation had been done to reduce the diameter. I was able to get the pully to stay on by pressing it ALL THE WAY on. That was enough to get the pully up over the shoulder. It engauged about 1/8" of the shaft that way. Just enough to work (for a while). This also put the pully too far in causing the belt to run slightly onto the radius of the pully. I had bought a new belt but I put it behind the seat and put the old belt back on. It lasted about 3 hours. Long enough for me to haul the trailer down the the camp sight plus a day or two of local driving, then it started coming apart, so I put the new belt on. When I bought the belt at CarQuest (where and when I bought the pullyer) they didn't ask me any questions about the truck and sold me a 111 5/8" belt. WOW was that a bear to put on! I had one guy hold the tensioner all the way over, while I slid under the truck where I was finally able to slide the belt up onto the Idler pully from the bottom side. Apparently, there are 2 different belts available (excluding the ambulance package) and I got the shorter belt of the two. In the mean time, I had called Rock Auto about vacuum pump pully problem. Apparently, in late '92, the diameter of the pully changed. My truck has a build date of 04/93, and should have had the smaller diameter pully. I work in the auto industry, so I know exactly how this happens. I got some left over parts on my truck. They shipped me a pump to fit an early 92. I drove home on Tuesday and the pump was waiting for me. On the way home I picked up another (longer) belt. I checked the pump shaft with the original pump (which I had kept with me) and it measured the same as the new replacment. I pulled the first replacment off, and went to mount the new replacement only to find out that on the new replacement the holes were threaded instead of clearance drilled. I called Rock Auto again, and let them know about the problem. Rather than go through another exchange, I just drilled the holes out. I had to get back on the road at 5:00 AM and I wanted the issue resolved before I left. The bolt pattern was the same, so I checked the hole size on the factory original and the other replacement. They measured 0.385" so I grabbed a 3/8 drill bit and chucked it in the drill press. The bolts measure 0.312" so the 3/8 bit gave me plenty of room. 2 min later it was ready to mount. Got it all put back on and everything worked fine. I'm still not sure what pump part number I should have ordered, but what I have now works.
I also called a dealership to find out what a new pully would cost. For the older style (bigger shaft) the pully was $71, and for the newer style, it was $40.
That's my story and I'm stick'n too it.
Mark
Here's my story:
First off, I called the local parts store, and they didn't have anything in stock. The part they could get me was a rebuilt Cardone. Rock Auto had the same pump for $40 less, so I bought it from them. When I got it, the shaft on the pump was a smaller diameter than the original. The original measures 0.669" with a pair of calipers. The replacement measured 0.650". There was actually a small step very close to the pump where it looked like an extra grinding operation had been done to reduce the diameter. I was able to get the pully to stay on by pressing it ALL THE WAY on. That was enough to get the pully up over the shoulder. It engauged about 1/8" of the shaft that way. Just enough to work (for a while). This also put the pully too far in causing the belt to run slightly onto the radius of the pully. I had bought a new belt but I put it behind the seat and put the old belt back on. It lasted about 3 hours. Long enough for me to haul the trailer down the the camp sight plus a day or two of local driving, then it started coming apart, so I put the new belt on. When I bought the belt at CarQuest (where and when I bought the pullyer) they didn't ask me any questions about the truck and sold me a 111 5/8" belt. WOW was that a bear to put on! I had one guy hold the tensioner all the way over, while I slid under the truck where I was finally able to slide the belt up onto the Idler pully from the bottom side. Apparently, there are 2 different belts available (excluding the ambulance package) and I got the shorter belt of the two. In the mean time, I had called Rock Auto about vacuum pump pully problem. Apparently, in late '92, the diameter of the pully changed. My truck has a build date of 04/93, and should have had the smaller diameter pully. I work in the auto industry, so I know exactly how this happens. I got some left over parts on my truck. They shipped me a pump to fit an early 92. I drove home on Tuesday and the pump was waiting for me. On the way home I picked up another (longer) belt. I checked the pump shaft with the original pump (which I had kept with me) and it measured the same as the new replacment. I pulled the first replacment off, and went to mount the new replacement only to find out that on the new replacement the holes were threaded instead of clearance drilled. I called Rock Auto again, and let them know about the problem. Rather than go through another exchange, I just drilled the holes out. I had to get back on the road at 5:00 AM and I wanted the issue resolved before I left. The bolt pattern was the same, so I checked the hole size on the factory original and the other replacement. They measured 0.385" so I grabbed a 3/8 drill bit and chucked it in the drill press. The bolts measure 0.312" so the 3/8 bit gave me plenty of room. 2 min later it was ready to mount. Got it all put back on and everything worked fine. I'm still not sure what pump part number I should have ordered, but what I have now works.
I also called a dealership to find out what a new pully would cost. For the older style (bigger shaft) the pully was $71, and for the newer style, it was $40.
That's my story and I'm stick'n too it.
Mark
