6066 (1960-1966) GMC Truck Club - Eaton spring experience / review

1966 GMC 1500 truck, coils in front, leafs in rear.

So rear leafs seemed to have a 10 leaf count that seemed extra stiff even for a 3/4 ton truck. Called eaton Detroit springs and ordered a set of c20 3/4 ton springs, original spring rate of 2000lbs. Original height, springs looked well made, middle bolt was loose but I tighten it to match the other side. Install on left passenger side was a breeze, no issues. Got to the right side and found the spring to be a bit tweaked, took a while but got them installed. It took a few weeks to realize I should have painted them, they rusted at least on the surface rather fast. Felt the ride difference, smoother and not jarring. Only problem is that right side I believe lays a bit flatter the then left as it has a slight lean.

On to the fronts, that had heavy duty springs per chevy 3/4 ton standards but GMC called them regular weight eaton MC2022. They arrived and looked identical to the ones I took off the truck, from height to coil thickness and pig tail end orientation. Perfect duplicate. But I wanted a lighter spring rate.

So I discovered that Eaton has GMC spring rate 1018lbs MC2022 as standard duty for that year. And heavy duty was even higher in spring weight.

For some reason the chevy c20 version has MC1766 rated at 710 lbs spring rate and the MC2022 as heavy-duty. Only thing I could figure is the engines the GMC version 351e is heavier then the engines in the chevy c20 version. But I have a sbc350 so I went with the lighter MC1766 version which us standard duty in the chevy c20.

Well I have the MC2022 sitting waiting for the MC1766 version to arrive. They finally do and when compared to the MC2022 version they are a bit taller and the thickness is thinner which makes sense since they take the different weight to compress. But the D shape end at the top and the pig tail at the bottom are in a different orientation then the original and the MC2022 heavy-duty spring.

Common sense would tell me I was going to have issues putting them in and I decided to call eaton springs. So I told them about my concerns regarding the orientation of the spring ends, they stated that's the way they all are, with not much other advise other then I can return them. Or try them because they should fit.

Surprise, I was right the orientation at the bottom would not allow them to fully seat in the cup in the spring tower. Well it took me a long time and with a come along and dropping the spring back out resetting and using the weight of the truck I forced them in. I still dont believe they are in correctly but the d shape in the tower was in and the lower control arm was in. So I moved on to the other side. Holy smokes, compared to the first coil the second was even more difficult. Took forever.

Finally got everything button up and took a test drive. Felt smoother for sure, I feel if I get better shocks I can improve it even more. I seem to be getting a bouncing feeling in the rear. Have the Yellow monroe truck shocks, will probably go with the KYB Gass adjust or just there standard excel g shock but we will see.

Bottom line am I happy? Kinda, eaton seems to make a decent product but I feel their quality control could be better and they could research more into the problems people run into on thier products. Would I buy again, probably but I wouldn't say they are the end all be all of suspension as they hail themselves to be. They are OK.

Hopefully this helps someone going through the same. Thanks.