This sentence is grammatically correct. But does it make sense to use word dissimilar to avoid repetition of different here?
the results would be absolutely dissimilar if there is any slight difference in the coefficients.
Writing type: formal
Most writers on English style deprecate what is mockingly called "elegant variation", using synonyms purely in order to avoid repetition. Using different words suggests to a reader that two different concepts are involved, which is clearly not the case in your example. You make your point more strongly by using the same word with explicitly contrasted terms to emphasize the difference in degree:
The results will be significantly different if there is even an apparently insignificant difference in the coefficients.