🔧 BUILD Upside-down M90 GTP build thread

General Information

When your wife gives you permission to build a racecar, you build a racecar.

This is what happened to me. However, all funding for this project comes out of my construction account. I really need a telehandler, so this is very budget friendly. Luckily, I've been stockpiling parts for years. This isn't an overnight build by any means. My goal is to make a 1/4 mile pass with it before the tracks close for the season. I'm taking a risk here and using photobucket for image hosting, so hopefully they don't screw me over again.

So let's start it off. I bought a 04 L26 motor with somewhere north of 100k on it and started to tear it down.

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Everything looks good so far. The pistons are really clean. There was some junk sitting in the oil pan, but not much.

GTPpower

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You can see why I'm losing boost. That lever is supposed to be up against the set screw, but it's a ways away.

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Got all my transmission parts in.

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Pulled the engine today. It's really hard to pull the engine with all this still on it. I broke a few pieces doing it.

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But the transmission is ready to come out. I drained the fluid. Lots of clutch material for only 100 miles on it.

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Ron Vogel

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I don't have any other gen V's. I would sacrifice a gen 3 for that though. But there's no way I could keep the belt from slipping with that setup
Did you add an idler pulley to get more wrap yet? I had good success with doing that. I also knurled my sc pulley.

On pump gas I dynoed 290 with a 2.5” full exhaust. I was trapping 111 then, same setup was trapping 117 on e85with some tuning. Could never get that car to hook right on slicks. Stuck at 12.0

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GTPpower

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Jun 5, 2012
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Did you add an idler pulley to get more wrap yet? I had good success with doing that. I also knurled my sc pulley.

On pump gas I dynoed 290 with a 2.5” full exhaust. I was trapping 111 then, same setup was trapping 117 on e85with some tuning. Could never get that car to hook right on slicks. Stuck at 12.0

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I haven't tried the wrap yet, mostly because I'd have to make one and it appears that the belt is not slipping yet. Once this thing builds boost like it should, we will see if I need more wrap.
 

GTPpower

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Ok, do after talking to a builder that does a lot of these, I'm waiting for parts again. I ordered a new forward band. I went with the high energy band. That sprag also feels rough to me, so I decided to replace it. This is the older pawl style. The newer style is ratcheting and it's stronger, so I'm going that route. It also requires different input clutches, so those are ordered as well. I should hopefully be able to start putting it back together next week.

In the meantime, I have a few different projects I'm doing.

Here's one...the brakes suck. So, out goes the jegs brake booster, and I'm working on setting it up with a Silverado hydroboost. I need to get some hydraulic hoses made, but this should be really easy to do. Other than that, I just need a piece of 3/16" steel to mount it to. IMG_20200814_172149186.jpg

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GTPpower

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Siiiiick! Hydraboost is nice. I considered that on my GN when the PM took a crap, but I didn't want to tap into the original hoses and risk overloading the pump. I converted to vacuum instead. Are you going to upgrade your pump or anything?

I'm going to just use the stock pump. I do have a Silverado pump, but it's significantly bigger, and I doubt it would fit. I think the stock pump should be ok though. A couple people have made this switch and haven't had any problems.
 

GTPpower

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Tried to get the hydraulic hoses made this morning, but I struck out. No one had the fittings I needed, so we'll have to try a different place next week.

In the meantime, I got a decent headstart on my tranny pan extension.

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It's all tacked into place. I just need to finish welding all the way around. Should have used the mig because this is taking forever.
 

GTPpower

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The pan is done, I just need to paint it. The filter extension I was going to use didn't end up working. I was told it fit....it does, but very poorly. And the pan would need to be extended 2" to work. (Remember this car has no weight reduction spared). So I had a machinist friend make me a new one that works with the pan I made.

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GTPpower

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I had a hell of a time getting the 3rd piston into place. I couldn't get it to drop in for the life of me. I pushed about as hard as a could, and it still wouldn't drop in. Come to find out that the transgo shift kit uses a crappy inner seal with a spring/wire to tighten it up. The seal sucks, so I used the stock seal. It's really hard to remove the spring, but I finally got it. But still couldn't get the piston to drop in. I worked on that for a long time, and finally looked closer at the groove....there appeared to be another one in there.

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There ended up being two. Wow.

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The piston dropped right in after that.


Other than that, it's coming together nicely. All the bands are in, and everything to the input and 3rd clutches. IMG_20200829_162503609.jpg

Im leaving 2nd out for now so I can get a thicker steel to tighten up the clearances on it.

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