How-to: checking bellhousing alignment / runout - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**LEEVON** · 10-12-2010, 01:07 AM

Well, this is my first manual trans install and I like to be prepared. My preparations led me to understand that bellhousing alignment is critically important for transmission function and longevity. It should always be verified and adjusted (if necessary) when installing a manual transmission. There are a couple of tutorials out there in cyberspace, but none here. I found out this is pretty easy, the hardest part is setting up a dial indicator.

Step 1: Mock-up your dial indicator so it is located roughly in the center bore of the bellhousing. I didn't think a magnetic base would work, so I fabbed (and I use the term loosely) a rigid piece of metal to firmly hold the indicator and provide a little adjustment. Here's a look at what I made, it bolts straight to the crank and there's a slot for the dial indicator, which I fastened with a 2" bolt and three nuts to adjust it. With the slot I made and the bolt it could adjust in both axis. It's important that the indicator be in the same plane as the mounting surface, and it will fit in the bore.

Step 2: Install bellhousing onto the engine block (without flywheel or clutch) and snug up the bolts.

Step 3: Rotate the crank, finding near center and zero out your dial indicator and make a mark at that location.

Step 4: Rotate the engine about 30-45 degrees (pick one, keep it consistent). Make a mark where you stop and note the runout. Rotate again and do the same until you have marked the bellhousing in a complete circle.

Step 5: You are comparing these measurements against each other in planes. If you have a reading of .010 directly opposite of -.006, subtract one from the other and divide by 2 to determine which way the bore is shifted. In this case, you have .004/2 = .002 or "2 thousandths".

Step 6: Runout should not exceed .010. In my case all measurements opposite each other were less than .010 so I'm good to go. However if your runout exceeds .010 you will need to source bellhousing alignment dowels, which I believe are available in increments such as .007, .014, .021.

If I'm off the mark or missed something please feel free to add to this thread.

D13 · 10-12-2010, 06:52 AM

Thanks! I've always just 'slapped them on' but now I have a much better visual on how to do this.

raycow · 10-12-2010, 03:13 PM

Leevon, you found an A833 for your truck? I have never seen one on an LSx before. Do you have any other pics of your swap?

Ray

**LEEVON** · 10-12-2010, 03:19 PM

Yes but I wasn't really looking for it. I had this trans and about three others in mind so when it popped up on Craigslist I bought it. Nicoslam sold two on here the other day in about 24 hours. I sand blasted it, that's why it's so clean, other than than I have no idea of it's condition, just figured if it's bad or I don't like it I can change it out easy enough. Some rock-crawler guy figured out the cheap and easy way to put a GenIII engine to a GenI trans, I just copied his parts so I can't take credit there (not that smart). Here's a couple of pics I have, and if you go to the link to my build below you can see the full write-up.

raycow · 10-13-2010, 11:24 AM

Thank you for the link. Your build is impressive and that is an extremely well detailed and informative write-up.

Ray

10-12-2010, 01:07 AM	#1
LEEVON Registered User Join Date: Jul 2006 Location: Ozark, MO Posts: 4,887	How-to: checking bellhousing alignment / runout Well, this is my first manual trans install and I like to be prepared. My preparations led me to understand that bellhousing alignment is critically important for transmission function and longevity. It should always be verified and adjusted (if necessary) when installing a manual transmission. There are a couple of tutorials out there in cyberspace, but none here. I found out this is pretty easy, the hardest part is setting up a dial indicator. Step 1: Mock-up your dial indicator so it is located roughly in the center bore of the bellhousing. I didn't think a magnetic base would work, so I fabbed (and I use the term loosely) a rigid piece of metal to firmly hold the indicator and provide a little adjustment. Here's a look at what I made, it bolts straight to the crank and there's a slot for the dial indicator, which I fastened with a 2" bolt and three nuts to adjust it. With the slot I made and the bolt it could adjust in both axis. It's important that the indicator be in the same plane as the mounting surface, and it will fit in the bore. Step 2: Install bellhousing onto the engine block (without flywheel or clutch) and snug up the bolts. Step 3: Rotate the crank, finding near center and zero out your dial indicator and make a mark at that location. Step 4: Rotate the engine about 30-45 degrees (pick one, keep it consistent). Make a mark where you stop and note the runout. Rotate again and do the same until you have marked the bellhousing in a complete circle. Step 5: You are comparing these measurements against each other in planes. If you have a reading of .010 directly opposite of -.006, subtract one from the other and divide by 2 to determine which way the bore is shifted. In this case, you have .004/2 = .002 or "2 thousandths". Step 6: Runout should not exceed .010. In my case all measurements opposite each other were less than .010 so I'm good to go. However if your runout exceeds .010 you will need to source bellhousing alignment dowels, which I believe are available in increments such as .007, .014, .021. If I'm off the mark or missed something please feel free to add to this thread. Attached Images __________________ '20 Silverado Trail Boss ~ '17 Tahoe ~ '79 K15 Sierra Grande ~ '76 Blazer 2wd ~ '71 Cheyenne swb ~ '55 Pontiac Safari ~'50 3100 bagged ~ '80 Wife ~ Late model kids Last edited by LEEVON; 10-12-2010 at 01:25 AM.

10-12-2010, 06:52 AM	#2
D13 Registered User Join Date: Feb 2007 Location: Memphis MI Posts: 1,851	Re: How-to: checking bellhousing alignment / runout Thanks! I've always just 'slapped them on' but now I have a much better visual on how to do this. __________________ 1987 2 ton 1982 250/TH350 beater in progress Dad's 1981 3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping Plus a mess o' tractors

10-12-2010, 03:13 PM	#3
raycow Registered User Join Date: Mar 2003 Location: San Francisco, CA USA Posts: 2,454	Re: How-to: checking bellhousing alignment / runout Leevon, you found an A833 for your truck? I have never seen one on an LSx before. Do you have any other pics of your swap? Ray Last edited by raycow; 10-12-2010 at 03:16 PM.

10-12-2010, 03:19 PM	#4
LEEVON Registered User Join Date: Jul 2006 Location: Ozark, MO Posts: 4,887	Re: How-to: checking bellhousing alignment / runout Yes but I wasn't really looking for it. I had this trans and about three others in mind so when it popped up on Craigslist I bought it. Nicoslam sold two on here the other day in about 24 hours. I sand blasted it, that's why it's so clean, other than than I have no idea of it's condition, just figured if it's bad or I don't like it I can change it out easy enough. Some rock-crawler guy figured out the cheap and easy way to put a GenIII engine to a GenI trans, I just copied his parts so I can't take credit there (not that smart). Here's a couple of pics I have, and if you go to the link to my build below you can see the full write-up. __________________ '20 Silverado Trail Boss ~ '17 Tahoe ~ '79 K15 Sierra Grande ~ '76 Blazer 2wd ~ '71 Cheyenne swb ~ '55 Pontiac Safari ~'50 3100 bagged ~ '80 Wife ~ Late model kids Last edited by LEEVON; 10-12-2010 at 03:23 PM.

10-13-2010, 11:24 AM	#5
raycow Registered User Join Date: Mar 2003 Location: San Francisco, CA USA Posts: 2,454	Re: How-to: checking bellhousing alignment / runout Thank you for the link. Your build is impressive and that is an extremely well detailed and informative write-up. Ray



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