[AlphaScent]

Does anyone have a good reference for the explanation of the gamma-gauche effect? 

[pgk]

It is generally accepted that the gauche effect is due to hyperconjugation. Indicatively, see below:
The Fluorine Gauche Effect: A Brief History, Israel Journal of Chemistry, 57(1-2), 92-100, (2017)
http://onlinelibrary.wiley.com/doi/10.1002/ijch.201600038/full
The C–F bond as a conformational tool in organic and biological chemistry, Beilstein Journal of Organic Chemistry, 6(38), (2016), e-article,  doi:10.3762/bjoc.6.38
https://www.beilstein-journals.org/bjoc/content/pdf/1860-5397-6-38.pdf
But let’s take a look to the issue from another point of view:
In general, anti-conformation is more stable due to energy minimization by zeroing of the dipole moment. But if dimers are formed via H….F bond, then the dipole moment of anti- conformation is not zero any more. Remember that H….F bond is very strong (≈ 40 kcal/mole), compared to H-bonds of other heteroatoms (3-7 kcal/mol). On the other hand, dipole moment is a question of angle, which might explain why the monomer conformer of ≈ 60o is more stable than the dimer anti-conformer.
Besides, strong O...H attractions also appear in electronic calculations of 1,2-dimethoxyethane, which is also susceptible to the gauche-effect:
Conformations of 1,2-Dimethoxyethane from ab initio Electronic Structure Calculations, J. Phys. Chem., 1993, 97 (49), pp 12745-12751, 97(49), (1993)
http://pubs.acs.org/doi/abs/10.1021/j100151a020?journalCode=jpchax
https://www.researchgate.net/publication/231399875_Conformations_of_12-Dimethoxyethane_from_ab_initio_Electronic_Structure_Calculations

[AlphaScent]

I apologize, I should have been more specific.  The gamma-gauche effect results in an up field shift of a carbon in fixed cyclic molecules (no ring flip).  I have a small explanation in a book but it is not enough.

Thank you for the references. I appreciate it. 

[wildfyr]

By upfield, do you mean in an NMR spectrum?

[pgk]

In that case, γ-gauche effect might be caused by a variety of factors, such as steric substituents, rings strain, presence of bridged rings with strained conformation, etc. On the other hand, up field shifts might not directly be associated with the γ-gauche effect.
I hope that the following references can be useful.
Substituent Chemical Shifts (SCS) in NMR, Part 6, A Model for the Calculation of Proton Chemical Shifts in Substituted Alkanes
http://www.modgraph.co.uk/Downloads/Chemical%20shifts%20of%20substituted%20alkanes.pdf
Ab Initio Calculations of Possible γ-Gauche Effects in the  13C-NMR for Methine and Carbonyl Carbons in Precise Polyethylene Acrylic Acid Copolymers, Molecules 2013, 18, 9010-9020
www.mdpi.com/1420-3049/18/8/9010/pdf

[AlphaScent]

Apologies for not being specific, again. The effect is seen in the C13 spectrum.  The fixed molecules I am working with are spiroketals.

Thanks again for the *delete me*

[pgk]

Little by little and with the tea spoon!
Spiroketals are susceptible to the anomeric effect, which is something similar; meaning that the thermodynamically unstable conformer is apparently the most stable one. Anomeric effect is caused by similar factors, as in the fixed rings and may strongly relate with the γ-gauche effect.
https://www.scripps.edu/baran/images/grpmtgpdf/Krawczuk_Nov_05.pdf