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Discussion Starter · #1 ·
Hi all, it has been a long while since I have posted anything. That's good news in that my swap has been chugging along these 5 years or so. bad news in that I haven't contributed or learned much.
I am at a loss as to the best way to address this problem.
I originally converted my '94 K2500 to 4BD2T power using a DieselTim adapter and the original NV4500 transmission. That seemed to work fine, but it did have a lot of rollover noise at idle. I just put that down to a relatively light flywheel and four almost one liter cylinders slugging it out up front.
A year or three in, I let someone use the truck and they lugged the engine down badly, slowing the truck almost to a crawl with the brakes while still in 4th gear. Shortly after that the clutch felt funny.
So I pulled it apart and found a couple things. Several of the springs were knocked out of the damper on the clutch disc and laying in the bottom of the bellhousing. Also the bronze/oilite pilot bearing had spun in the back of the crank and was loose.
So, I replaced the disc with a McLeod disc, a decent brand name in the US at least. Replaced the clutch pressure plate with another new aftermarket Isuzu one, turned a new pilot bushing on the lathe with a good interference fit on the back of the crank.
Now, I was concerned about the alignment of the whole belhousing/adapter package because I didn't see how the pilot bearing problem was related to the clutch disc problem. So I took the whole mess to a friends machine shop with inspection equipment and we indicated everything in perfectly concentric. It was a little off to start with but not much. Once it was perfect I pinned all the pieces together so they can't move. I reassembled everything and it seemed good to go.
That was January 2020, and I used the truck all year in its usual duty, mostly just driving around but also pulling fairly heavy trailers a couple times. Then recently I noticed that the transmission seemed noisier than usual in 1st thru third. So I pulled one of the PTO covers off and had a look inside. Low and behold almost all the teeth on the front most counter shaft gear were damaged. OK, well, those were aftermarket parts when I built the transmission (you have to swap in a Dodge input shaft and front counter shaft gear to make the adapter kit work) so maybe they were just crap.
So I pulled it apart again. And again the clutch plate damper springs are damaged. Not falling out yet, but several cracked and broken though still captive in their pockets.
And the pilot bushing is trashed again.
I'm kind of at loss because there's little I can do about any damage that is being caused by just engine vibration. I am very confident of the work we did to make sure the adapter and bell housing are all on the same centerline. And I was pretty confident on my .0015" interference fit on the pilot bearing.
I don't really want to do this job again in another year.
Appreciate any thoughts! ( I did search the forum)
Thanks,
Phil
 

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Is the adapter housing stiff enough? It may be flexing out of alignment when the load comes on or with vertical forces from road shock.
 

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I had 2 LUK clutch discs behind my 4BT for the Ford/Cummins adapter the one from the bread van had springs in it that were MUCH heavier that the ones in the replacement disc, the replacement was for the f series pickups. I'm thinking that there might be multiple applications depending on GVW's.
 

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Discussion Starter · #4 ·
Thanks for the replies! The adapter is just an aluminum plate that goes between the stock Isuzu bell housing and the transmission. It is 1/2" thick and doesn't have hardly any bending moment applied to it. Very similar to this:
131637


The original application for the clutch disc is unknown. I just went to the McLeod website and picked a 12" disc with the correct 1-1/4 x 12 spline.....
 

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I have a disc hanging on the wall , it’s been there for years . 4 out of the 6 damper springs were laying in the bellhousing also . I was thinking the issue with mine was , using the clutch to stop the engine from rotating during shutdowns . But I’m not sure . My disc was a 12 in gasser disc , from a Dodge nv4500 . Any else determine what is the issue , please help .
 

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Thanks for the replies! The adapter is just an aluminum plate that goes between the stock Isuzu bell housing and the transmission. It is 1/2" thick and doesn't have hardly any bending moment applied to it. Very similar to this:
View attachment 131637

The original application for the clutch disc is unknown. I just went to the McLeod website and picked a 12" disc with the correct 1-1/4 x 12 spline.....
Clutch disc not holding up could easily be a disc without the torque capacity. But it's the centre bush getting chewed up that's making me question alignment.
If you can make the same geometry plate out of steel it will be 3 times stiff but also 3 times heavier.

Stock Isuzu uses a bearing for the shaft.
 

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Discussion Starter · #7 ·
Thanks for the replies again. I am going to use a ball bearing this time for the pilot bearing. South Bend Clutch is supposed to be able to make me a disc with a heavy duty Diesel oriented center section, working with them now.
Understand about duplicating the adapter in steel.... I'll let y'all know how it turns out.
Thanks!
Phil
 
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