T10 conversion
07-12-2011, 06:48 PM
#12
Here are tips I copied from an article a good while back that may give you some ideas about what is required to bolt an older style manual transmission behind a Gen III/IV engine. Keep in mind, this is not my writing, nor have I used any of the suggestions listed below to confirm their validity.
Manual Trans Swaps
When GM decided to build the new Gen III small-block that would become the LS1, GM's engineers carried over a couple of important design characteristics that make it easy to retrofit newer engines into older cars. It's doubtful that GM considered car crafters' requirements when it designed these new Gen III/IV engines, but regardless of the company's agenda, it did us a couple of big favors. The first gift is that the Gen III/IV bellhousing pattern is almost identical to the original small-block Chevy. Five of the six bellhousing bolts are in exactly the same location, as are the size and location of the two dowel pins. This one fact allows us to make everything else work. The Gen III/IV bolt pattern is not symmetrical, which is odd, and the top center bolt is employed while the upper passenger side bolt is not. But if using five of the six bolts works for you, then everything else is easy. As you will see, there are plenty of options that allow you to use all six bolts.
Unfortunately, GM engineers also added a few hurdles just to make this swap game more challenging. First and foremost, the crankshaft flange on a Gen III/IV engine is essentially even with the bellhousing flange on the block. On the original small-block and big-block Chevy engines, the crankshaft flange extends 0.400 inch farther rearward (aft, if you're nautically inclined) of the bellhousing flange. This is the critical differential measurement that defines all the other modifications we have to make to adapt earlier transmissions.
Another important piece to this swap puzzle is that all Gen III/IV engines use a distinct crankshaft mounting flange. This means now we have three separate crank flanges: the Gen I small-block with a two-piece rear main seal, the Gen I with a one-piece rear main seal, and now the Gen III/IV engines with their one-piece rear main seal. While this should come as no surprise, the Gen III/IV engines are now completely metric, demanding all new fasteners. Obviously, this means Gen I flywheels and flexplates will not interchange with a Gen IIII/IV engine. One other important tech tidbit is that all Gen III/IV engines use a 168-tooth flywheel or flexplate.
Given all this, the quickest way to adapt an early four- or five-speed manual trans to a Gen III/IV engine is to make up this 0.400-inch difference in crankshaft flange position. McLeod Clutches, which was recently purchased by B&M, has solved this problem with a 168-tooth flywheel that will bolt up to the Gen III/IV crankshaft and extends the flywheel face by exactly 0.400 inch. This places the clutch and pressure plate surface at the correct height so you can either bolt on a new clutch and pressure plate assembly or use a Gen I clutch and pressure plate assembly you already have. This custom McLeod flywheel is drilled to accept the traditional 11-inch Borg & Beck/diaphragm-style pressure plate bolt pattern using original 3/8-inch shouldered pressure plate bolts.
Before we bolt on the bellhousing, there is one other crucial step that must not be overlooked. It should be common knowledge that a pilot bushing positioned in the end of the crankshaft supports the transmission input shaft, preventing deflection when the clutch is disengaged. In our trans-swapping effort, remember that while the depth of our bellhousing is the same as with a Gen I engine, the crankshaft flange is 0.400 inch farther forward. Since the input shaft length on our traditional four-speed or five-speed transmission has not changed, we also have to move the position of the pilot bushing rearward to compensate for the discrepancy. McLeod has again come to the rescue with an adapter pilot bushing that sits in the larger recess in the crank and therefore supports the input shaft in the proper location. If you don't pay attention and incorrectly place a stock pilot bushing in the original spot in the Gen III/IV crank, the transmission input shaft will not be supported and the input shaft bearing will fail almost immediately. We also discovered that GM makes a special LS2/LS7 pilot bearing that will adequately support the shorter input shaft.
This brings us to the bellhousing. Because all Gen III/IV engines use a 168-tooth flywheel and flexplate diameter, not all small-block Chevy bellhousings will work when it comes to bolting on an older four- or five-speed manual trans. This larger flywheel requires the rare 11-inch-style bellhousing. To use the larger flywheel, you'll either have to dig up a used 11-inch bellhousing or scattershield, or you can order a brand-new aluminum factory-style bellhousing from Keisler that will not only accommodate the larger flywheel but is drilled for the Gen I and Gen III/IV bolt patterns. One thing we discovered is the Keisler bellhousing is cast 0.200 inch deeper than a standard GM bellhousing. The standard GM bellhousing depth is 6.290 inches from the engine bellhousing face to the transmission mounting face, while the Keisler specs out at 6.490 inches. This affects input shaft placement relative to the crank as well as the position of the clutch disc. Another option is using a scattershield from Quick Times that also combines the Gen III/IV bolt pattern with the standard Gen I-style bell-housing depth.
The McLeod adapter flywheel (left) offsets the distance to the flywheel friction surface rearward (toward the transmission) an additional 0.400 inch to make up for the shorter crank flange position on Gen III/IV engines. Note the Gen III/IV flywheel bolt pattern is smaller than the Gen I bolt pattern (right). The McLeod flywheel is relieved on the backside to maintain its 35-pound weight.
Even using the custom offset McLeod flywheel, this custom McLeod pilot bushing adapter is necessary to properly support the input shaft.
The Keisler aluminum bellhousing employs both the Gen I and III/IV bolt patterns so it can be used on either engine. Of course, an 11-inch Gen I small- or big-block bellhousing can also be used as long as you're willing to sacrifice one mounting bolt hole. Standard small-block 101/2-inch (153-tooth) bellhousings will bolt up to a Gen III/IV engine but won't clear the 168-tooth flywheel.
We're not quite there yet. We prefer to keep everything simple by retaining the original mechanical clutch linkage, avoiding the added expense of a hydraulic system. The problem is Gen III/IV engines do not have a provision in the block for the engine-mounted ball stud pivot for the clutch linkage Z-bar. While discussing this with Scoggin-Dickey Parts Center's (SDPC) Nickey Fowler, he mentioned SDPC makes an adapter bracket originally designed for the Gen V/VI factory Rat blocks that also did not come with this ball stud provision. This SDPC bracket bolts to the lower two bellhousing bolts on the driver side and places the ball stud in exactly the right position for the Z-bar. This is the best scenario for adapting a Gen I-style manual trans behind a Gen III/IV engine that is easy and not overly expensive.
Not-So Shortcuts
Car crafters are the masters of adapting parts to achieve a solution. As you might have guessed, there are other ways to arrive at adapting a Gen I four- or five-speed manual trans behind a Gen III/IV engine. One idea involves using a Gen III/IV flywheel. Bolting on a stock metric Gen III/IV flywheel is easy, but again, it will also be short by 0.400 inch. According to McLeod, a production Gen III/IV pressure plate and clutch assembly stands roughly 1 inch taller than a Gen I diaphragm pressure plate. Even accounting for the shorter Gen III/IV flywheel, this places the metric pressure plate fingers roughly 0.600 inch taller than a Gen I system. Since this does not allow sufficient room for the release arm bearing, it won't work.
However, if you have a good Gen III/IV flywheel, you could have a machine shop drill it for the standard diaphragm counterbored bolt pattern using the correct 3/8-inch shouldered bolts. As you will discover, the stock metric pressure plate bolt pattern is the same as the Gen I 11-inch diaphragm pressure plate pattern. Do not use the Gen III metric bolt holes to attach an old-style pressure plate because these bolt holes are not counterbored and will not properly locate the pressure plate. All Gen III/IV metric pressure plates use a pair of small drive pins as locators. Since this conversion will use the 3/8x16 shouldered bolts, machining a separate bolt pattern and counterboring the bolt holes for the shouldered bolts will be necessary.
Manual Trans Swaps
When GM decided to build the new Gen III small-block that would become the LS1, GM's engineers carried over a couple of important design characteristics that make it easy to retrofit newer engines into older cars. It's doubtful that GM considered car crafters' requirements when it designed these new Gen III/IV engines, but regardless of the company's agenda, it did us a couple of big favors. The first gift is that the Gen III/IV bellhousing pattern is almost identical to the original small-block Chevy. Five of the six bellhousing bolts are in exactly the same location, as are the size and location of the two dowel pins. This one fact allows us to make everything else work. The Gen III/IV bolt pattern is not symmetrical, which is odd, and the top center bolt is employed while the upper passenger side bolt is not. But if using five of the six bolts works for you, then everything else is easy. As you will see, there are plenty of options that allow you to use all six bolts.
Unfortunately, GM engineers also added a few hurdles just to make this swap game more challenging. First and foremost, the crankshaft flange on a Gen III/IV engine is essentially even with the bellhousing flange on the block. On the original small-block and big-block Chevy engines, the crankshaft flange extends 0.400 inch farther rearward (aft, if you're nautically inclined) of the bellhousing flange. This is the critical differential measurement that defines all the other modifications we have to make to adapt earlier transmissions.
Another important piece to this swap puzzle is that all Gen III/IV engines use a distinct crankshaft mounting flange. This means now we have three separate crank flanges: the Gen I small-block with a two-piece rear main seal, the Gen I with a one-piece rear main seal, and now the Gen III/IV engines with their one-piece rear main seal. While this should come as no surprise, the Gen III/IV engines are now completely metric, demanding all new fasteners. Obviously, this means Gen I flywheels and flexplates will not interchange with a Gen IIII/IV engine. One other important tech tidbit is that all Gen III/IV engines use a 168-tooth flywheel or flexplate.
Given all this, the quickest way to adapt an early four- or five-speed manual trans to a Gen III/IV engine is to make up this 0.400-inch difference in crankshaft flange position. McLeod Clutches, which was recently purchased by B&M, has solved this problem with a 168-tooth flywheel that will bolt up to the Gen III/IV crankshaft and extends the flywheel face by exactly 0.400 inch. This places the clutch and pressure plate surface at the correct height so you can either bolt on a new clutch and pressure plate assembly or use a Gen I clutch and pressure plate assembly you already have. This custom McLeod flywheel is drilled to accept the traditional 11-inch Borg & Beck/diaphragm-style pressure plate bolt pattern using original 3/8-inch shouldered pressure plate bolts.
Before we bolt on the bellhousing, there is one other crucial step that must not be overlooked. It should be common knowledge that a pilot bushing positioned in the end of the crankshaft supports the transmission input shaft, preventing deflection when the clutch is disengaged. In our trans-swapping effort, remember that while the depth of our bellhousing is the same as with a Gen I engine, the crankshaft flange is 0.400 inch farther forward. Since the input shaft length on our traditional four-speed or five-speed transmission has not changed, we also have to move the position of the pilot bushing rearward to compensate for the discrepancy. McLeod has again come to the rescue with an adapter pilot bushing that sits in the larger recess in the crank and therefore supports the input shaft in the proper location. If you don't pay attention and incorrectly place a stock pilot bushing in the original spot in the Gen III/IV crank, the transmission input shaft will not be supported and the input shaft bearing will fail almost immediately. We also discovered that GM makes a special LS2/LS7 pilot bearing that will adequately support the shorter input shaft.
This brings us to the bellhousing. Because all Gen III/IV engines use a 168-tooth flywheel and flexplate diameter, not all small-block Chevy bellhousings will work when it comes to bolting on an older four- or five-speed manual trans. This larger flywheel requires the rare 11-inch-style bellhousing. To use the larger flywheel, you'll either have to dig up a used 11-inch bellhousing or scattershield, or you can order a brand-new aluminum factory-style bellhousing from Keisler that will not only accommodate the larger flywheel but is drilled for the Gen I and Gen III/IV bolt patterns. One thing we discovered is the Keisler bellhousing is cast 0.200 inch deeper than a standard GM bellhousing. The standard GM bellhousing depth is 6.290 inches from the engine bellhousing face to the transmission mounting face, while the Keisler specs out at 6.490 inches. This affects input shaft placement relative to the crank as well as the position of the clutch disc. Another option is using a scattershield from Quick Times that also combines the Gen III/IV bolt pattern with the standard Gen I-style bell-housing depth.
The McLeod adapter flywheel (left) offsets the distance to the flywheel friction surface rearward (toward the transmission) an additional 0.400 inch to make up for the shorter crank flange position on Gen III/IV engines. Note the Gen III/IV flywheel bolt pattern is smaller than the Gen I bolt pattern (right). The McLeod flywheel is relieved on the backside to maintain its 35-pound weight.
Even using the custom offset McLeod flywheel, this custom McLeod pilot bushing adapter is necessary to properly support the input shaft.
The Keisler aluminum bellhousing employs both the Gen I and III/IV bolt patterns so it can be used on either engine. Of course, an 11-inch Gen I small- or big-block bellhousing can also be used as long as you're willing to sacrifice one mounting bolt hole. Standard small-block 101/2-inch (153-tooth) bellhousings will bolt up to a Gen III/IV engine but won't clear the 168-tooth flywheel.
We're not quite there yet. We prefer to keep everything simple by retaining the original mechanical clutch linkage, avoiding the added expense of a hydraulic system. The problem is Gen III/IV engines do not have a provision in the block for the engine-mounted ball stud pivot for the clutch linkage Z-bar. While discussing this with Scoggin-Dickey Parts Center's (SDPC) Nickey Fowler, he mentioned SDPC makes an adapter bracket originally designed for the Gen V/VI factory Rat blocks that also did not come with this ball stud provision. This SDPC bracket bolts to the lower two bellhousing bolts on the driver side and places the ball stud in exactly the right position for the Z-bar. This is the best scenario for adapting a Gen I-style manual trans behind a Gen III/IV engine that is easy and not overly expensive.
Not-So Shortcuts
Car crafters are the masters of adapting parts to achieve a solution. As you might have guessed, there are other ways to arrive at adapting a Gen I four- or five-speed manual trans behind a Gen III/IV engine. One idea involves using a Gen III/IV flywheel. Bolting on a stock metric Gen III/IV flywheel is easy, but again, it will also be short by 0.400 inch. According to McLeod, a production Gen III/IV pressure plate and clutch assembly stands roughly 1 inch taller than a Gen I diaphragm pressure plate. Even accounting for the shorter Gen III/IV flywheel, this places the metric pressure plate fingers roughly 0.600 inch taller than a Gen I system. Since this does not allow sufficient room for the release arm bearing, it won't work.
However, if you have a good Gen III/IV flywheel, you could have a machine shop drill it for the standard diaphragm counterbored bolt pattern using the correct 3/8-inch shouldered bolts. As you will discover, the stock metric pressure plate bolt pattern is the same as the Gen I 11-inch diaphragm pressure plate pattern. Do not use the Gen III metric bolt holes to attach an old-style pressure plate because these bolt holes are not counterbored and will not properly locate the pressure plate. All Gen III/IV metric pressure plates use a pair of small drive pins as locators. Since this conversion will use the 3/8x16 shouldered bolts, machining a separate bolt pattern and counterboring the bolt holes for the shouldered bolts will be necessary.
05-14-2013, 09:03 PM
#13
Staging Lane
Join Date: Nov 2012
Location: Slidell, LA
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So what ever happened here?
Would like to know cause I have a 4.8 with a ranny issue n would like to swap in my
M20 Muncie. Not crying over the overdrive either cause the truck is on 24's.
[IMG]<a href="http://s192.photobucket.com/user/zukboi2004/media/IMG_3215.jpg.html" target="_blank"><img src="http://i192.photobucket.com/albums/z241/zukboi2004/IMG_3215.jpg" border="0" alt=" photo IMG_3215.jpg"/></a>[/IMG]
[IMG]
[/IMG]
Would like to know cause I have a 4.8 with a ranny issue n would like to swap in my
M20 Muncie. Not crying over the overdrive either cause the truck is on 24's.
[IMG]<a href="http://s192.photobucket.com/user/zukboi2004/media/IMG_3215.jpg.html" target="_blank"><img src="http://i192.photobucket.com/albums/z241/zukboi2004/IMG_3215.jpg" border="0" alt=" photo IMG_3215.jpg"/></a>[/IMG]
[IMG]
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Last edited by zukboi2004; 05-14-2013 at 09:04 PM. Reason: picdidnt post
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