The property of well-orderability is upward absolute for transitive models of ZF: by Replacement in the smaller class, specifically Mostowski collapse, this is equivalent to the upward absoluteness of von Neumann ordinals, which holds, by Foundation in the larger class, since the property of being a von Neumann ordinal is captured by the $\Delta\_0$ condition "transitive and linearly 
ordered by membership".


Note that Foundation is already necessary for the corresponding absoluteness result concerning finiteness 
[Is $\omega$ absolute in set theory without foundation?](https://mathoverflow.net/questions/85941/is-omega-absolute-in-set-theory-without-foundation):


Is upward absoluteness true or, perhaps more interestingly, independent in the absence of Replacement?



Absoluteness of well-orderability
Upward absoluteness of well-foundedness fails for transitive models of Zermelo set theory (i.e. with full Separation but no Replacement). That is, you can find $M \subseteq N$ both transitive models of Zermelo so that there's a linear order $L \in M$ which $M$ thinks is a well-order but $N$ sees is ill-founded.


This follows from Theorem 2.2 of Harvey Friedman's 1973 paper "Countable models of set theories" (<https://doi.org/10.1007/BFb0066789>). Let me state an instance of the theorem suitable for this question.



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> Let $\alpha$ be a countable admissible ordinal and let $T$ be a theory in the language of set theory which extends KP so that $T$ has a transitive model with $\alpha$ as an element. Then there is an ill-founded model of $T$ whose well-founded part has height exactly $\alpha$.
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(Briefly: You can prove this using the Barwise compactness theorem. Doing it for $T$ being ZFC: Let $U$ be a countable model of ZFC with $\alpha \in U$ admissible. Then $A = \mathrm L\_\alpha$ is an admissible set. You can cook up a theory $E$ in the infinitary language $\mathcal L\_A$ whose models must be end-extensions of $A$ whose well-founded parts have height $\alpha$. (Here, $Y \supseteq X$ is an end-extension if for any $a \in X$ if $Y \models b \in a$ then $b \in X$.) Then $U$ witnesses that $A$-finite fragments of $E$ + ZFC are consistent, and so by Barwise compactness $E$ + ZFC has a model.)


Let $\bar M$ be a model of ZFC obtained from this theorem for countable admissible $\alpha > \omega$. ZFC proves that $\mathrm V\_{\omega + \omega}$ is a model of Zermelo set theory, and set $M = {\mathrm V\_{\omega+\omega}}^{\bar M}$. In Zermelo, well-foundedness is a $\Pi\_1$-property. These are downward absolute among end-extensions. (That's really the same fact that $\Pi\_1$-properties are downward absolute among transitive models.) So everything in $M$ which $\bar M$ thinks is well-founded is also thought to be well-founded by $M$. In particular, everything $\bar M$ thinks is a countable ordinal is isomorphic to a linear order on $\omega$ in $M$, which $M$ thinks is a well-order. Fix such a linear order $L$, isomorphic to an "ordinal" $\lambda$ in the ill-founded part of $\bar M$.


Now observe that $M$ is well-founded—because $M$ has height $\omega+\omega < \alpha$ and $\bar M$ is well-founded below $\alpha$. So $M$ is a transitive model of Zermelo which thinks $L$ is a well-order. But $N = \mathrm V\_{\omega+\omega}$ sees that actually $L$ is ill-founded. This is because $N$ contains every real and so has a witness to the ill-foundedness of $L$. Thus the desired pair $M \subseteq N$.


