95' Junker Drag Truck

when i racked my barrels the truck ran fine. idle wasnt the greatest but i liked mine as low as i could get with the 5k in there so it wasnt always happy at an idle. other than that it ran great.

Garrett
 
Mine was done maybe 8 years ago by Wimer Diesel, there not farm from me in PA. 215 pump no problems its just a noisy sucker. We racked dads 180 and fired it up, played with the idle and the gsk both couldnt beleive how smooth it is.
 
Well, my one and only pass this last Friday night was a failure. I burned up the forward clutch pack in my transmission. I've been fighting dips in line pressure for quite a while and I guess the forward clutch pack was the weak link.

Once I get the tranny torn down, I'll post pictures of the burned clutches and any other carnage I find. I was able to drive home but anything more than 10% throttle would cause the transmission to slip.

I don't have the time slip in front of me right now, but it was 13.3xx with less than 100 MPH trap speed. The truck seemed a little sluggish off the line and when full boost came on in 3rd gear, the truck revved to almost 5000 rpm as it blew through the (4) friction double belleville spring forward clutch pack. Line pressure has been dipping to around 145 psi for a half second during lock-up and 155psi during overdrive engagement so that's most likely the cause of the failure at my moderate horsepower level. I plan to closely inspect the bushings, seals, and crackable hard parts to see where the pressure dips are coming from.
 
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YOUNG GUNS15 said:
no chatter?
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No chatter, no burnt fluid, no signs of slippage till halfway through the pass.

After that run, I let it cool off for a bit then drove it around in the pits, it definitely slips into gear smooth and sloppy, before it would slam into gear pretty hard. Driving around in the pits, the 1-2 gear shift is soft and you can barely feel the gear shift, before it used to chirp the tires shifting into 2nd gear just normal driving. If you lock the converter in 2nd or 3rd gear and roll into it, once boost comes up enough to where it's putting out about 125 HP or so, it starts slipping. On the highway in overdrive, converter locked or unlocked, give it about 10% throttle and starts slipping.

All "forward" gears slip, therefore, I'm 95% sure the problem is a burned up forward clutch pack. Whether or not it's just glazed-over, or burned all the friction material down to metal, I don't know yet.
 
are you still running the stock pump? maybe an aftermarket pump or a constant pressure valve body might be in line? for the future
 
crackerman said:
are you still running the stock pump? maybe an aftermarket pump or a constant pressure valve body might be in line? for the future
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It still has the stock transmission pump. I haven't seen or heard of anyone making an aftermarket tranny pump for these things. I've seen pumps with coated gears to help lower pump noise and supposedly reduce wear, but nothing about higher flow.

I'll scratch my head a little more when I open it up and see if there are any places I can do a little port/polish work to help free up the feed passage to the pump. It might be time to ditch the factory filter and run a large brass screen-type filter as well... although I don't know of any high performance trucks running special filters, maybe this is a "trade secret"...
 
Sorry to hear you hurt your trans. I thought the line pressure issues were with the old trans not the new one. I have to be honest I am looking forward to your rebuild due to the fact that after reading the entire thing four times my auto trans knowledge grew exponentially!

Big Blue24 said:
most likely the cause of the failure at my moderate horsepower level.
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Your definition of moderate makes me laughLOL:clap:
 
yah after reading your clutch pack upgrades, im pulling mine out before i even get to test it and doing that so now i have to wait till you put a new tranny post lol
 
straight 6 roar said:
Pump gears could be worn? I'm sure theres a spec you could check with a feeler gauge
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I'll definitely check the pump gears for wear and see if they are still within spec. They were brand new the first time I built this tranny because the original gears where marred up from a broken stock converter hub ear that tumbled around in the pump for who knows how long before I bought the truck.
 
Mild Tranny Carnage

I pulled the transmission last night (3 hours) I know I'm slow but to pull the tranny on my race truck there are a few extra steps: prop the truck up 18" so there is room to work under there, remove 90% of the twin turbo setup, remove the relocated transmission heat exchanger, remove both driveshaft loops, remove the homebuilt 5" exhaust system....

Anyway, my diagnosis was correct, the forward clutch pack was burned up. I created an experimental setup last time for this clutch pack and that's probably 90% of the reason for failure. The experimental clutch pack involved removing the plastic cushion spacer, installing two belleville springs instead of one, stock pressure plate, 4 clutches and 5 steels, flipped over pressure plate instead of stock .280" thick flat reaction plate, stock waved snap ring. The first thing I noticed is that the 4th clutch was just barely catching the splines on the ring gear and so it basically wasn't engaged, so right away I had a 3-clutch pack instead of 4. It also looks like the belleville springs flexed far enough to make contact with the planetary that mounts on the end of the intermediate shaft.

In this case a picture is worth a thousand words since I'm sure the above description is foggy at best:

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If you look closely, you can see the extra steel I added between the last friction that wasn't engaging and the modified reaction plate. I added the extra steel to try to make sure the 4th clutch would fully engage the splines on the forward ring gear, but as you can clearly see in the picture, the 4th clutch was too close to the edge of the splines on the ring gear and it was not engaging.

Transmission02.jpg
 
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I also tore down the pump and had a look inside. Everything looked fine to me, all of the teflon seals were in-tact and in great shape. The dimpled bushing looked just fine as well, although for good measure, I'm going to replace all the bushings this go around.

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For me it looks like crack in input shaft , near the hole ...
 
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