I'm trying to compile some transmission bellhousing depths for clutch clearance information, specifically for those who are interested in running multi-plate or reduced diameter clutches. If you have a transmission that you have access to, I would appreciate your help!
What I'm after: A measurement down from the bellhousing face to the tallest obstacle, inside a given radius. If there's a significant difference in height (let's say greater than 3/8") between a tall feature and the surrounding housing, take a note of what radius that feature starts and ends at. My goal at the end is to create clearance profile sketches for the commonly used transmissions. The more information you provide , the more accurate I will be in creating the sketches (provided I can make sense of it). I can include input shaft/TOB information also, just reference any dimensions from the bellhousing face or the input shaft C/L.
There are also 2 specific measurement windows (from the input shaft centerline) that will be helpful:
Depth inside R 4.4" (7.25" Clutch) Depth inside R 3.5" (5.5" Clutch)
Getrag 282: Depth inside R 4.4" : 2.46" Depth inside R 3.5" :
92-94 HTOB Getrag: Depth inside R 4.4" : 2.45" Depth inside R 3.5" :
Isuzu 5spd: Depth inside R 4.4" : 2.46" Depth inside R 3.5" :
Muncie 4spd: Depth inside R 4.4" : Depth inside R 3.5" :
The max clearance inside the transmission from the crank flange to the part of the case covering the output shaft is ~2.425".
According to http://www.tiltonracing.com/pdfs/82.pdf the distance from the button flywheel friction surface to the tips of the bolts on top of the clutch is 1.98". Making the button 0.400" thick leaves 0.045 clearance between the clutch and the transmission case. The bolts can be cut down to be flush with their nuts, freeing up an extra ~0.060 and allowing up to 0.450" button thickness. The bolts *may* be reversible so that the nuts would stay on the inside, but I'll have to get one in my hands to figure that out.
In order to fit a button this thin, I will have to bore a N* or V6 flexplate to the OD of the button and weld the remaining outer ring of the flexplate to the OD of the button. Oh well... the finished product will have lower MOI than it would by stacking a button on top of the flexplate.
The flywheel bolts can protrude above the friction surface by about 0.050 so long as they stay within the 5" ID of the friction material on the disks. ARP makes flywheel/flexplate bolts with thin heads. I'll have to see what they have in the way of 8x1.25 bolts. The N* crank flange is 0.575 thick and I know from experience that I want as little protrusion as possible beyond it. The factory bolts have a head thickness of 0.175, which means that the counterbores would have to be 0.125 deep. With a 0.450 thick button, this leaves 0.325 after the counterbore. 0.325 + 0.575 = 0.900 or about 23mm would be the best bolt length in that case.
I ordered a 62-002-5 Tilton TOB from Summit. I disassembled a stock Fiero TOB and may be able to use the housing with a small custom sleeve to fit the Tilton unit where it has to go... which is about 5/8" closer to the crank flange than the stock TOB sits.
[This message has been edited by Will (edited 09-16-2014).]
Here are the measurements I have. For the case depth, the two radii you have listed are the same for all transmissions. Also, the depth is limited by the aluminum bearing bosses for the transmission shafts.
Case End of End of Retraced Extended End of TOB Depth Input Shaft Splines TOB TOB Sleeve 92-94 HTOB Getrag: 2.454” -0.052” 0.316” 2.425” ------ ------ Isuzu: 2.462” 0.336” 0.562” 2.504” ------ 1.764” F23: ??? ??? ??? 2.776” 1.899” ------ F40: 3.513” 1.128” 1.527” 3.529” 2.660” ------
From those measurements that I was quoted in above the 3800 crank protrudes .035" from the engine bell housing flange. - you could add .035 to those measurements if you measure from the transmission bellhousing.
So for the F23 it's 3.040 There is about 10" diameter with that much clearance.
Case End of End of Retraced Extended End of TOB Depth Input Shaft Splines TOB TOB Sleeve 92-94 HTOB Getrag: 2.454” -0.052” 0.316” 2.425” ------ ------
When I measured my 92 FWD Getrag I came up with a pressure plate clearance from the bell housing surface to the inside of the trans to only be 2.325" and thus I needed to have my flywheel turned down to 0.820" for my 3800SC swap. I'm including the picture below I made at the time. Pay attention to the green line only.
When I made my post using this image I noted that the T/O bearing could compress down another 0.100" so maybe my measurement was correct but the actual clearance for the pressure plate needs to be 2.325" instead of the T/O clearance of 2.425" as in your table. So basically, I guess this is just a note for people looking at tolerances for the flywheel/pressure plate combo.
[This message has been edited by grsychckn (edited 09-24-2014).]
I can double check the bellhousing depth dimension when I get home, but I am pretty sure its was correct.
Over the years there have been several people do the 3800 swap who used a 0.84" thick flywheel and had pressure plate to bellhousing interference.
I have measured several 2.8's from the flywheel face to the engine bellhousing surface and all were 0.83 - 0.84. I think the 3800 swaps have had soooo many people do them that the flywheel "thickness" ended up being referenced as 0.840" instead of it being the "flywheel depth or protrusion". The actual flywheel thickness to get the right flywheel depth/protrusion is in the 0.82" range.
Hopefully this info can help others too. My Spec 3 had no clearance issues with my WCF 0.840 flywheel. I swapped to a stock pressure plate from autozone and the top of the pressure plate barely rubs inside the bellhousing.
Since the flywheel needs to be resurfaced anyway, I took it to the machine shop this morning. They measured the thickness at 0.870 inches. So maybe it wasn't milled down correctly to begin with. Or maybe surface rust and measuring inaccuracy accounts for the additional 0.030. He's taking off another 0.050 and said that he could go as far as 0.150 more if need be before the flywheel runs out of meat.
[This message has been edited by 2002z28ssconv (edited 02-09-2015).]