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Going to try some dirt drag racing with the Tahoe

n8in8or

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Thread starter #1
I found out a couple months ago that KOI Dirt Drag Racing was going to be coming to the second annual diesel show put on by Legendary Diesel. This sounded like something to try out! I know the Tahoe could never compete in truck pulls with its short wheelbase and low weight (not to mention not having as much power as the other guys), but this seemed like something I could try and be somewhat competitive. Plus being on dirt, maybe I won’t break. Well today’s the day! So far the rain has held off, so we’ll see how this goes! 98B9F146-71C7-4C48-9104-1D855963B0F3.jpeg
 

n8in8or

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Practice is over. Unfortunately I am here by myself so it’s hard getting my time slips. I did get a couple and I’m running about 4.5 seconds at my best on the 200’ track. I won some and I lost some during practice. It’s a pro tree, so that’s interesting to get used to.

Technically I should be in the Mod class because of my non-factory turbo housing, but since I’m the only 6.5, they wanted me to be competitive so they are letting me run in the Street class that is supposed to be stock appearing turbos, but the insides can be modded. I think it was very nice of them to do that and I sure appreciate it since it would be no fun to have my ass handed to me run after run. I hooked up pretty good when the track was dry, but then they put some water down I was spinning a lot. I aired down to 36psi and that helped. After a few runs my trans gets in the 210+ range, so I need to keep an eye on that. In the driver’s meeting he said that he breaks up the diesel classes so the trucks don’t get too hot. Overall I’m very impressed with how this operation is run.

Unfortunately, my faux pro camera stopped working wih my phone for remote control, so I can’t do the videos I hoped to do.....and since my brother isn’t here I won’t have any outside vids. Maybe I can get a fellow racer to take a vid or 2 for you.
 

n8in8or

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Pushed through my brakes while building boost and red lighted. :oops: Didn’t happen once during time trials. Luckily it’s double elimination, but already one of my chances is gone. Dammit!
 

schiker

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Pendleton, SC
#13
You represented very well. Yeah, reaction time difference more than loss margin so close.

Looks like the other truck was a dually (yes no? ) and the rear was low like he added weight to help traction or was modified? He also looked to have bigger wider tires. So him with more power, better traction but heavier (double edge sword on dirt?). Versus the newer technology, you ran really competitively. Congrats.

Thanks for sharing.
 

n8in8or

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Thread starter #14
You represented very well. Yeah, reaction time difference more than loss margin so close.

Looks like the other truck was a dually (yes no? ) and the rear was low like he added weight to help traction or was modified? He also looked to have bigger wider tires. So him with more power, better traction but heavier (double edge sword on dirt?). Versus the newer technology, you ran really competitively. Congrats.

Thanks for sharing.
Thanks! Yeah I need more practice building boost while concentrating on the tree. Maybe I’ll go up to the local paved strip during test n tune nights for more practice.

The other truck wasn’t a dually. His back was a little low, but I think he was just going for a specific look. He had really wide wheels with tires that weren’t quite as wide if that makes sense. The tires didn’t have an aggressive tread pattern, but he seemed to hook pretty well. I’m not sure how weight factors in on dirt. I was thinking my lower weight helped me since I was down on power, but then my shorter wheelbase probably helps in conjunction with the lower weight - like it maintains weight density yet I don’t have the penalty of overall mass to move if that makes sense?

I think I have a good start here that just needs some optimizing. I think I’m losing a lot through my transmission. I was hoping to build a new trans this winter with stuff from Jake’s - we’ll see how my money situation is....
 

n8in8or

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Thread starter #15
A couple more notes on last night:

Tires. I installed new tires last weekend. A couple reasons for that: 1. Because the tread was getting a little low on my Mastercraft Courser AXTs and I didn’t want that to hold me back for the dirt drags. 2. I’d like to get some late model wheels next year I think and so I wanted to try a different tire size and see if I was happy. I can sell these used for nearly what I have invested in them this fall when I put my winter tires on, so my experiment wouldn’t cost much. This is also part of my experiment of going from 3.73 to 3.42 gears (which I AM liking so far - 1st gear is much more usable for me than it was before). So I went from 265/70/16 to 265/75/16, not a huge jump, but a little jump in diameter. The main nugget here is that the new tires are Hankook Dynapro ATM tires. They are reviewed pretty well overall and have a good cost. I was concerned that the overall tread pattern wasn’t agressive enough and would hold me back, but that was only true when the track got really wet - but once I dropped the pressure from 44 to 36 (warm) that took care of the problem for the most part. You apparentlu don’t need an aggressive mud tire to have enough traction for dirt drag racing - at least not on the track I was on.

F3ED0E05-BD1D-46B9-A4B3-3F3908EC2FD3.jpeg EAF25731-AC3C-4F10-84A3-8D23AA46BCF8.jpeg D37FEE36-2C24-4C81-874E-E36BC8481958.jpeg

Another note - trans fluid. I have had Valvoline Dexron/Mercon synthetic in my trans since it was rebuilt (I think in 2015?) which is a Dexron VI fluid. Once I did the Moose conversion I’ve been unhappy with how loose my converter is. When the torque converter clutch kicks in THAT’S when the truck pulls the hardest. I was reading on fluids and read that Dexron VI is thinner than Dexron III and you should run III in a trans that was designed for it. Then I was also reading that John Deere Hy-Gard is a great upgrade for automatic transmissions and has a viscosity similar to Dexron III. Guys have said their stall speed dropped a little with it and it holds up to heat really well. Well, knowing I’d be hammering the trans for the races it seemed like a good time to change. I also put this fluid in last weekend, so I’ve only been driving on it for a week. It did seem to tighten the converter a little, but I have nothing to measure that with so that’s just going by my butt dyno which is sometimes unreliable. The real nugget here is that I worked the trans hard last night doing boosted launches run after run with less than 10 minutes in between. At one point the tran temp gauge was over 210 degrees which worried me so I drove around some in an attempt to lower it (it didn’t really help), but finally shutting it off for 15-20 minutes did. I need to do the electric fan clutch Les did so I can turn the fan on manually to get more airflow when parked. Anyway....I just checked the fluid and it’s still clear and smells fine. Now I may not have gotten it so hot to where it would have actually burnt, but I thought I would share the info anyway.

0A8649BC-ED26-4E45-8610-27B513AC190B.jpeg
 

schiker

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#20
Exactly. Use it to help build boost before launch and cool during staging then cut to lowest lock up to race? It would be nice if it reacted that fast but unlikely. Maybe Leroy's electric clutch.

I have seen a few trucks with the lowered back end and don't really like the look. I saw one with lifted front, lowered rear, and sets the tailgate open 1/4. Kinda a poser look. Looks like it makes visibility poor. To each his own but not for me. I don't like my truck to sag even when loaded.

My understanding is aggressive open lugs are good for clearing heavy sticky mud. Kinda depends on your dirt. I would think you judge it by how much the tire loads up and ease of clean out???

How about your tie rods? Did you feel a lot of pull steering or bad wobble? I thought ya'll both took off pretty straight with a little squirm at first And how about your new rear end. Don't you like that little positive traction squirm in the back end but hooking with front to pull diagonal too.
 
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