When I installed mine on my '72 I have a R200 diff and only shaved off the bottom 3/4 inch layer. It fits really snug but everything went back together fine. Is there a chance it is too tight of a fit?

I'm installing one right now on my '73 240z with r180 using the urethane top bumper and a stock lower mount if any curious parties want to see anything specific in the process, but I'm not bothering to document the whole thing because it has been done before a few times.

I'm using the one from TechnoVersions and I swear it fits better than most of the gloves I own, the difference between being able to test fit it and not was scrubbing off the thin layer of road grime on the underbody.

QUESTION: Why can't you use the GM 3-1108 mount in place of the your stock differential mount?

QUESTION: Why can't you use the GM 3-1108 mount in place of the your stock differential mount?

You can. The design that everyone copied though is the original Ron Tyler design, which he intended for a small block chevy engine application. Word is that it lowers the nose of the differential and may or may not lead to vibration from drive shaft misalignment when used with the L6.

I'm surprised that none of the guys that sell these haven't tweaked the design to work best with the L6.

So I can buy the Gm 31108 Mount for $28, and have a better quality mount than the factory differential mount which costs about $50? I'm running a stock L28, so I don't figure i need the R/T mount... but if I had the LS1 conversion, I would definitely consider it.

I've remembered another problem with using the 3-1108 with the RT design. The heads of the long bolts that pass through the differential might interfere with the top of the crossmember. Some people grind the GM mount to get clearance, others drill holes in the top of the crossmember. You might get on to Hybridz and search a little, you'll probably find some pictures. The design really needs to be modified to use the 3-1108 for L6 use. Ron Tyler put the dimensions on the web and they're just been copied directly, for V8 applications.

I have a mount similar to the RT design with a GM 3-1108 mount but it sits higher in the tunnel. I made it myself though. You'll have to put a lot of extra work in to use one you buy off the internet, unless you use a snubber.

For the cost and trouble, in retrospect, I would probably just buy a new stock mount. New rubber is tough. It's fun to modify though.

I have had vibration issues, but my issue might be complicated by the fact that I run a BWT-5 trans from a 83 turbo. I had to fab my own mount(trans) to make things work. That itself might have changed the stock driveshaft angle. The RT mount with the GM mount does lower the diff front enough to be an issue with the stock bracket. I think for stock L6 trans I would use the urethane stop with the stock diff mount to 'sandwich' the diff to keep it from moving.

I just tossed in the 3-1108 and it cured most of my clunk, however the vibration at 65-70 is ridiculous. If I never got on the highway it would be fine. I will be trying the bump snubber later on tonight. I was just hoping to use the GM mount as I paid for it and it looked like it would be easier to work on in some regards.

If you had a way to measure DS angle it might be a clue of what's happening. It's kind of hard to find a good place to put a magnetic protractor , but that would tell you what your angles are. That's seems to be about the right speed for the vibes from what I have researched.

My wife is on the way to harbor freight at the moment to pick up an angle gauge. Just for giggles I am going to toss in the original mount, measure the angle, and then try to duplicate it with the GM mount. If all else fails I will just use the factory mount and cut down snubber.

let us know

I may have had some misalignment in my initial set-up. The pinion angle was 87 degrees on the passenger side and 86 drivers side. The transmission was showing 87 degrees as well so I thought everything should be kosher.

Since everything is so easy to get to with the RT mount I went ahead and swapped in the snubber and factory mount to check the measurements. It ended up 85 degrees all the way across.

I gave it a quick test drive and most of the clunk is gone again, and the thrumming vibration at 65-70 is gone as well. In both instances the car gets more vibration from 70-80, but it is more of a whole car feeling and not alarming.

I believe the GM mount was more secure feeling than the combination snubber and factory mount. So if I get more time I may modify it to take a few degrees out of the pinion angle.

Too bad most of my cure was actually from tightening up the rear differential mounts that had backed out over time. I think that really covered around 80% of the clunk.