LM7 and 4l60E have arrived . Build thread will follow.

[90gmcsierraL59]

On the road to pick up the GMC

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[L31MaxExpress]

On the road to pick up the GMC

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Sweet, enjoy that thing. Looks nicely done.

 

[90gmcsierraL59]

We arrived right on schedule snd took a test drive. It is like driving a different truck. The throttle response is instantaneous. It accelerates hard and the shifts are firm but nothing outrageous. The difference in power is unbelievable. My license may be in jeopardy. We loaded up the K motor and my travel tote with vital fluids and took Adam out to a nice steak late lunch early dinner. Then we gassed up and got on the road. The exhaust note is deep and throaty but not loud unless you get on it hard (and even then all you really hear is the fan , which will be changed sooner rather than later). On the interstate the tach reads slightly higher at speed than the Kmotor did about 200 RPMs. Initially I thought it might not be going into lock up so I tested it like my friend who owns the transmission shop told me to by holding steady on the accelerator steady and tapping the brake to unlock the converter, which confirms lock up by the tach going up 200 RPM and dropping back down. Unbeknownst to me Adam told me if it wasn't going into lock up that a CEL would come on as the TCM would show it as a fault.
The ride home was uneventful and a lot of fun. The L59 makes power from idle and you really have to watch your speed or set the cruise like I did as the smooth power delivery is deceptive and 80 MPH in that light truck is effortless. Of course right before we got off I-95 at Fredericksburg we encountered a traffic jam that had us running 5 MPH starting and stopping every 6 feet for 25 minutes. We got back to Front Royal about 2115 and gassed up again to check the mileage and even with the K motor and other cargo in the bed and the starts and stops running 77 on the interstates it got 18.9 MPG for the trip home. I think with reasonable speeds and unladen 20 is attainable. Checked all the vital fluids this morning and all were perfect. I crawled under and rolled around on the creeper and no leaks were noted. I am very happy with the swap. Thanks Adam!!! And thanks to everyone here for the encouragement, advice and well wishes.

 

[90gmcsierraL59]

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[90gmcsierraL59]

The L59 and 4l60E continues to impress me. It is so smooth. Averaging near 19 MPG on the 122 mile round trip commute. I have 1100 miles on it so far and I couldnt be more pleased. The only thing that I have any issues with is the very noisy fan. It sounds like a helicopter in the cab if you step down on it. So I ordered an electric fan kit today.

 

[90gmcsierraL59]

2500 mile update:
Tailshaft stopped seeping. No other leaks noted. Averaging 18.5 MPG on the 122 mile daily commute as long as I maintain 75 MPH mostly with the cruise set on the interstate. This proves difficult because it really likes to run between 80 and 85...Neither engine oil nor transmission fluid have moved from the full marks. I am gathering parts to install the electric fans. After consulting with Adam and another friend who have installed similar setups we will be using a continuous duty solenoid to prolong relay and fan controller life and a manual over ride switch in the cab in case of relay or controller failure. I have family coming for a 2 week visit starting Friday so shop time will be severely limited until Mid-November. More to follow.

 

[BeXtreme]

I am gathering parts to install the electric fans. After consulting with Adam and another friend who have installed similar setups we will be using a continuous duty solenoid to prolong relay and fan controller life and a manual over ride switch in the cab in case of relay or controller failure.

If you properly install and wire a system just like the stock 2006+ Suburban/Silverado electric fans, you shouldn't have any issue with relays. My 2011 Suburban is at 240k miles and I've never had a relay failure. My 1980 K25 has the same dual electric fan system from a 2013 K2500 pickup and it has been working just fine for about 3 years now with no failures of any kind.

 

[62barsoom]

Very well done. That MPG is astounding!

 

[90gmcsierraL59]

Thanks. Yeah if I play at all it will drop to 17. Lowest for a tank of hard running was 16.5. But I'm not sure I had it full on that one. Setting the cruise as much as possible really helps. It rarely shifts down unless it is a big hill. I bought aftermarket fans and this setup is a bit more complex than the single universal flex a lite that I installed in my 65 Falcon Ranchero 5.0 HO conversion in the 90s with a relay and a toggle switch on the dash. I guess I could have saved myself some money if I had researched further for a GM fan setup that would fit my 17x28 radiator but hindsight is always 20/20.

 

[GrimsterGMC]

Thanks. Yeah if I play at all it will drop to 17. Lowest for a tank of hard running was 16.5. But I'm not sure I had it full on that one. Setting the cruise as much as possible really helps. It rarely shifts down unless it is a big hill. I bought aftermarket fans and this setup is a bit more complex than the single universal flex a lite that I installed in my 65 Falcon Ranchero 5.0 HO conversion in the 90s with a relay and a toggle switch on the dash. I guess I could have saved myself some money if I had researched further for a GM fan setup that would fit my 17x28 radiator but hindsight is always 20/20.

I find that the cruise control can trim the throttle far gentler than my right foot so I make use of it when ever I can.