Transmissions and Drivetrain Need help with your trans? Problems with your axle?

Bellhousing/Scattersheild alignment

Old 01-21-2019, 01:24 PM
  #1  
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Join Date: Nov 2007
Location: milwaukee
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Car: 04 silverado 4X4 6 speed/ 91 Z28
Engine: LS1
Transmission: T56
Axle/Gears: Moser 9" 3.70 35 spline wavetrack
Bellhousing/Scattersheild alignment

So I end up needing a bellhousing and look at prices only to determine the scattersheild would be a good choice. At twice the price and the power level I am at, I do not need it. On the other hand if I was to find out I should have had one, I would really regret not having it. So I purchase the Quicktime T56 LS version. Reviewing the instructions, they emphasize the alignment is crucial and the instructions to do that are vague. Google to the rescue with assistance from youtube. The recommended procedure is to remove the front transmission plate and torque it to the scattersheild and use a dial indicator to center/align the input shaft bearing race. I have the tools and understand the concept of what is to be accomplished here. It did not work, not at all. I went through the entire procedure a number of times repeating my numbers time and time again. I determined that I needed the offset dowel pins, purchased them, installed them, adjusted them, and the math worked. The math told me it was good, TIR of .003. I started with a TIR of .0105 - .011 I used .007 offset pins. When I bolted the transmission to the engine without the clutch installed it was difficult to rotate the yoke on the output shaft. No, not undoable just difficult. I thought perhaps something went wrong when I reinstalled the front plate of the transmission. I separated the trans from the engine and the trans spun freely again. So now I am confused, when is the last time math lied to you? I am confident I messed up somewhere I just dont know where. My friend who has raced modifieds told me what he had done. Bolt the trans to the bellhousing and to pull the dowels out and leave the bolts in loosely for the bellhousing. Move it around until the trans spins freely tighten the bolts and go. Kinda makes sense so I tried that with some other steps included. I do have a torqueometer, 0-30 in.lbs. quite sensitive. I measured the rotational force required to turn the trans in all 6 forward gears with the trans separate from the engine and recorded the numbers. I purchased another set of pins at .014 offset and after installing and adjusting them I came to spot where I can repeat the same rotational force as recorded earlier or no resistance. I feel this is good, but I am curious as to what people with experience with this issue think. Also curious on any theory as to why the first attempt failed when the indicator said it was good.
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Old 01-21-2019, 08:01 PM
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jmd
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Re: Bellhousing/Scattersheild alignment

Separation of assemblies so you are measuring what matters is important.
​​​​​​
Every time "my input shaft has lateral play!!!!!!!" comes up, it is by someone who has the transmission on a bench (no pilot bearing) and just knows that something is wrong. But they haven't measured bearing endplay. Yet.

Work on seeing whether the face of the new bell is flat, relative to the engine. Your dial should let you do this. Then, resume checking runout. Yeah, the faceplate removal and setup to measure it is a pain. But, setup of the bell is important and you gotta do it.

And further, the reassembly of the tremec front case plate can have bearing races get cocked or stuck, leading you to believe the bell offset is at fault when it is not. So *remove the trans. from the equation.*

Your buddies' method is possibly relevant but has a lot of holes in how it works. Namely, it probably works a little bit with an assembled trans. but the 8 bolt Tremec setup changes that. A little offset with a bronze bushing will not be a huge deal. The self-destruction roller bearings are another ballgame.

Wade through the hard work.
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Old 01-25-2019, 07:50 AM
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Join Date: Nov 2007
Location: milwaukee
Posts: 298
Car: 04 silverado 4X4 6 speed/ 91 Z28
Engine: LS1
Transmission: T56
Axle/Gears: Moser 9" 3.70 35 spline wavetrack
Re: Bellhousing/Scattersheild alignment

QUOTE=jmd;6276085]Separation of assemblies so you are measuring what matters is important.

​​​​​​???

Every time "my input shaft has lateral play!!!!!!!" comes up, it is by someone who has the transmission on a bench (no pilot bearing) and just knows that something is wrong. But they haven't measured bearing endplay. Yet.

I never said anything like this, why did you bring it up ? Please elaborate. I did rebuild the transmission some time ago. I replaced all of the bearings and performed the shimming procedure setting everything at the tight end of the tolerance. My input shaft has a little lateral play but does not flop around.

Work on seeing whether the face of the new bell is flat, relative to the engine. Your dial should let you do this. Then, resume checking runout. Yeah, the faceplate removal and setup to measure it is a pain. But, setup of the bell is important and you gotta do it.

It is 0 on top and + 0.006 at 6 o'clock. I have come across many recommendations to remove the powder coating to ensure that the difference in coating thickness is not skewing the mating surface on either side of the bellhousing. Also that is recommended for hole in the bellhousing when using an older transmission and centering that hole does the job. Since this is a T56 I am mounting the front plate of the trans to the bellhousing and centering the input shaft hole with the race installed. Because of this I believe removing the powder coating to be a moot point.

And further, the reassembly of the tremec front case plate can have bearing races get cocked or stuck, leading you to believe the bell offset is at fault when it is not. So *remove the trans. from the equation.*

I picked up a no walk bushing and installed that as well. So I broke down the trans into sub assembly's just to clean the mating surfaces of the main case, front plate, and tail housing. The shimming procedure has some tight tolerances and I did not want any residual silicone effecting those clearances nor did I want any debris inside the transmission. My first reaction was to blame myself for possibly getting something misaligned during reassembly, but everything spun freely once the trans was disconnected from the engine.

Your buddies' method is possibly relevant but has a lot of holes in how it works. Namely, it probably works a little bit with an assembled trans. but the 8 bolt Tremec setup changes that. A little offset with a bronze bushing will not be a huge deal. The self-destruction roller bearings are another ballgame.

Perhaps I was not clear, the trans is reassembled without any silicone sealer on the front plate mating surface. I will apply the sealer when I am satisfied that the bell is lined up and I am done pulling that plate off. I welded a nut to an extra yoke so I could use a torque o meter to measure the rotational force required to turn the trans. I measured with the trans disconnected from the engine for base numbers. I then adjusted the pins until I could repeat those numbers or no resistance. Since first posting I have put the front plate/dial indicator back on and remeasured, made minor adjustments and now the dial indicator says I am good. I reassembled the trans and mounted it to the bellhousing and the torque o meter says I am good also. I just do not trust the dial indicator method.
As for my friends advice, I did not intend to portray his advice as gospel because he drives a RACECAR. He knows that he pulled his locating pins and he will be back in there again. I have offset pins and am not relying on just the bolts to keep things in place. It was his advice that got me to think to go by feel and then to use the tool to measure the feel.
Setting up the dial indicator is a pain no doubt. Getting it perpendicular to the bearing race is well, I got it close as I could and was totally surprised when the numbers were as close as they were.
The pilot bearing in my truck failed causing problems, it's been bushings ever since. I always assumed the factory pins were good. It wasn't until seeing the scattersheild instructions that I knew there was even a possibility of adjustment. Now after going through this procedure I am curious if a pilot bearing would be better.

Wade through the hard work.[/QUOTE]

So the indicator said I was dead on last time and this time. I went from .007 offset pins to .014 offset pins. That is what has me confused at this point.
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